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diff --git a/36504.txt b/36504.txt new file mode 100644 index 0000000..a7e48cd --- /dev/null +++ b/36504.txt @@ -0,0 +1,12818 @@ +The Project Gutenberg eBook, Freshwater Sponges, Hydroids & Polyzoa, by +Nelson Annandale + + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + + + + +Title: Freshwater Sponges, Hydroids & Polyzoa + + +Author: Nelson Annandale + + + +Release Date: June 24, 2011 [eBook #36504] + +Language: English + +Character set encoding: ISO-646-US (US-ASCII) + + +***START OF THE PROJECT GUTENBERG EBOOK FRESHWATER SPONGES, HYDROIDS & +POLYZOA*** + + +E-text prepared by Bryan Ness, Carol Brown, Sharon Joiner, and +the Online Distributed Proofreading Team (http://www.pgdp.net) +from page images generously made available by Internet Archive +(http://www.archive.org) + + + +Note: Project Gutenberg also has an HTML version of this + file which includes the original illustrations. + See 36504-h.htm or 36504-h.zip: + (http://www.gutenberg.org/files/36504/36504-h/36504-h.htm) + or + (http://www.gutenberg.org/files/36504/36504-h.zip) + + + Images of the original pages are available through + Internet Archive. See + http://www.archive.org/details/freshwatersponge00anna + + + + + +The Fauna of British India, Including Ceylon and Burma. + +Published Under the Authority of the Secretary of +State for India in Council. + +Edited by A. E. Shipley, M.A., Sc.D., HON. D.Sc., F.R.S. + + +FRESHWATER SPONGES, HYDROIDS & POLYZOA. + +by + +N. ANNANDALE, D.SC., + +Superintendent and Trustee (_Ex Officio_) of the Indian Museum, +Fellow of the Asiatic Society of Bengal and of the Calcutta University. + + + + + + + +London: +Taylor and Francis, Red Lion Court, Fleet Street. + +Calcutta: +Thacker, Spink, & Co. + +Bombay: +Thacker & Co., Limited. + +Berlin: +R. Friedlaender & Sohn, 11 Carlstrasse. + +August, 1911. + +Printed at Today & Tomorrow's Printers & Publishers, Faridabad + + + + +CONTENTS. + + Page + + EDITOR'S PREFACE v + + SYSTEMATIC INDEX vii + + GENERAL INTRODUCTION 1 + Biological Peculiarities 2 + Geographical Distribution 5 + Geographical List 7 + Special Localities 13 + Nomenclature and Terminology 17 + Material 20 + + INTRODUCTION TO PART I. (_Spongillidae_) 27 + The Phylum Porifera 27 + General Structure 29 + Skeleton and Spicules 33 + Colour and Odour 35 + External Form and Consistency 37 + Variation 39 + Nutrition 41 + Reproduction 41 + Development 45 + Habitat 47 + Animals and Plants commonly associated with Freshwater Sponges 49 + Freshwater Sponges in relation to Man 50 + Indian Spongillidae compared with those of other Countries 51 + Fossil Spongillidae 52 + Oriental Spongillidae not yet found in India 52 + History of the Study of Freshwater Sponges 54 + Literature 55 + + GLOSSARY OF TECHNICAL TERMS USED IN PART I. 61 + + SYSTEMATIC LIST OF THE INDIAN SPONGILLIDAE 63 + + INTRODUCTION TO PART II. (_Hydrida_) 129 + The Phylum Coelenterata and the Class Hydrozoa 129 + Structure of Hydra 130 + Capture and Ingestion of Prey: Digestion 133 + Colour 134 + Behaviour 135 + Reproduction 136 + Development of the Egg 139 + Enemies 139 + Coelenterates of Brackish Water 139 + Freshwater Coelenterates other than Hydra 141 + History of the Study of Hydra 142 + Bibliography of Hydra 143 + + GLOSSARY OF TECHNICAL TERMS USED IN PART II. 145 + + LIST OF THE INDIAN HYDRIDA 146 + + INTRODUCTION TO PART III. (_Ctenostomata_ and _Phylactolaemata_) 163 + Status and Structure of the Polyzoa 163 + Capture and Digestion of Food: Elimination of Waste Products 166 + Reproduction: Budding 168 + Development 170 + Movements 172 + Distribution of the Freshwater Polyzoa 173 + Polyzoa of Brackish Water 174 + History of the Study of Freshwater Polyzoa 177 + Bibliography of the Freshwater Polyzoa 178 + + GLOSSARY OF TECHNICAL TERMS USED IN PART III. 181 + + SYNOPSIS OF THE CLASSIFICATION OF THE POLYZOA 183 + + SYNOPSIS OF THE SUBCLASSES, ORDERS, AND SUBORDERS 183 + + SYNOPSIS OF THE LEADING CHARACTERS OF THE DIVISIONS OF + THE SUBORDER CTENOSTOMATA 185 + + SYSTEMATIC LIST OF THE INDIAN FRESHWATER POLYZOA 187 + + APPENDIX TO THE VOLUME 239 + Hints on the Preparation of Specimens 239 + + ADDENDA 242 + Part I. 242 + Part II. 245 + Part III. 245 + + ALPHABETICAL INDEX 249 + + EXPLANATION OF PLATES. + + + + +EDITOR'S PREFACE. + + +Dr. N. Annandale's volume on the Freshwater SPONGES, POLYZOA, and +HYDRIDA contains an account of three of the chief groups of freshwater +organisms. Although he deals mainly with Indian forms the book contains +an unusually full account of the life-history and bionomics of +freshwater Sponges, Polyzoa, and Hydrozoa. + +I have to thank Dr. Annandale for the great care he has taken in the +preparation of his manuscript for the press, and also the Trustees of +the Indian Museum, Calcutta, for their kindness in placing material at +the disposal of the Author. + + A. E. SHIPLEY. + Christ's College, Cambridge, + March 1911. + + + + + SYSTEMATIC INDEX. + + + Page + PORIFERA. + + Order HALICHONDRINA 65 + + Fam. 1. SPONGILLIDAE 65 + + 1. Spongilla, _Lamarck_ 67 + 1A. Euspongilla, _Vejdovsky_ 69 + 1. lacustris, _auct._ 69 + 1_a_. reticulata, _Annandale_ 71, 241 + 2. proliferens, _Annandale_ 72 + 3. alba, _Carter_ 76 + 3_a_. cerebellata, _Bowerbank_ 76 + 3_b_. bengalensis, _Annandale_ 77 + 4. cinerea, _Carter_ 79, 241 + 5. travancorica, _Annandale_ 81 + 6. hemephydatia, _Annandale_ 82 + 7. crateriformis (_Potts_) 83 + 1B. Eunapius, _J. E. Gray_ 86 + 8. carteri, _Carter_ 87, 241 + 8_a_. mollis, _Annandale_ 88 + 8_b_. cava, _Annandale_ 88 + 9. fragilis, _Leidy_ 95 + 9_a_. calcuttana, _Annandale_ 96 + 9_b_. decipiens, _Weber_ 97 + 10. gemina, _Annandale _ 97 + 11. crassissima, _Annandale_ 98 + 11_a_. crassior, _Annandale_ 98 + 1C. Stratospongilla, _Annandale_ 100 + 12. indica, _Annandale_ 100 + 13. bombayensis, _Carter_ 102, 241 + 13_a_. pneumatica, _Annandale_ 241 + 14. ultima, _Annandale_ 104 + 2. Pectispongilla, _Annandale_ 106 + 15. aurea, _Annandale_ 106 + 15 _a_. subspinosa, _Annandale_ 107 + 3. Ephydatia, _Lamouroux_ 108 + 16. meyeni (_Carter_) 108 + fluviatilis, _auct._ 242 + 4. Dosilia, _Gray_ 110 + 17. plumosa (_Carter_) 111 + 5. Trochospongilla, _Vejdovsky_ 113 + 18. latouchiana, _Annandale_ 115 + 19. phillottiana, _Annandale_ 117 + 20. pennsylvanica (_Potts_) 118 + 6. Tubella, _Carter_ 120 + 21. vesparioides, _Annandale_ 120 + 7. Corvospongilla, _Annandale_ 122 + 22. burmanica (_Kirkpatrick_) 123 + caunteri, _Annandale_ 243 + 23. lapidosa (_Annandale_) 124 + + HYDROZOA. + + Order ELEUTHEROBLASTEA 147 + + Fam. 1. HYDRIDAE 147 + + 1. Hydra, _Linne_ 147 + 24. vulgaris, _Pallas_ 148 + 25. oligactis, _Pallas_ 158, 245 + + POLYZOA. + + Order CTENOSTOMATA 189 + + Div. 1. Vesicularina 189 + + Fam. 1. VESICULARIDAE 189 + + 1. Bowerbankia, _Farre_ 189 + caudata, _Hincks_ 189 + bengalensis, _Annandale_ 189 + + Div. 2. Paludicellina 190 + + Fam. 1. PALUDICELLIDAE 191 + + 1. Paludicella, _Gervais_ 192 + 2. Victorella, _Kent_ 194 + 26. bengalensis, _Annandale_ 195 + + Fam. 2. HISLOPIIDAE 199 + + 1. Hislopia, _Carter_ 199 + 27. lacustris, _Carter_ 202 + 27 _a_. moniliformis, _Annandale_ 204 + + Order PHYLACTOLAEMATA 206 + + Div. 1. Plumatellina 206 + + Fam. 1. FREDERICELLIDAE 208 + + 1. Fredericella, _Gervais_ 208 + 28. indica, _Annandale_ 210, 245 + + Fam. 2. PLUMATELLIDAE 211 + + Subfam. A. _Plumatellinae_ 212 + + 1. Plumatella, _Lamarck_ 212 + 29. fruticosa, _Allman_ 217 + 30. emarginata, _Allman_ 220, 245 + 31. javanica, _Kraepelin_ 221 + 32. diffusa, _Leidy_ 223, 245 + 33. allmani, _Hancock_ 224, 246 + 34. tanganyikae, _Rousselet_ 225, 246 + 35. punctata, _Hancock_ 227 + 2. Stolella, _Annandale_ 229 + 36. indica, _Annandale_ 229 + himalayana, _Annandale_ 246 + + Subfam. B. _Lophopinae_ 231 + + 1. Lophopodella, _Rousselet_ 231 + 37. carteri (_Hyatt_) 232 + 37 _a_. himalayana (_Annandale_) 233 + 2. Pectinatella, _Leidy_ 235 + 38. burmanica, _Annandale_ 235 + + + + +GENERAL INTRODUCTION TO THE VOLUME. + + +Although some zoologists have recently revived the old belief that the +sponges and the coelenterates are closely allied, no one in recent times +has suggested that there is any morphological relationship between +either of these groups and the polyzoa. Personally I do not think that +any one of the three groups is allied to any other so far as anatomy is +concerned; but for biological reasons it is convenient to describe the +freshwater representatives of the three groups in one volume of the +"Fauna." + +Indeed, I originally proposed to the Editor that this volume should +include an account not only of the freshwater species, but of all those +that have been found in stagnant water of any kind. It is often +difficult to draw a line between the fauna of brackish ponds and marshes +and that of pure fresh water or that of the sea, and this is +particularly the case as regards the estuarine tracts of India and +Burma. + +Pelseneer[A] has expressed the opinion that the Black Sea and the +South-east of Asia are the two districts in the world most favourable +for the study of the origin of a freshwater fauna from a marine one. The +transition in particular from the Bay of Bengal, which is much less salt +than most seas, to the lower reaches of the Ganges or the Brahmaputra is +peculiarly easy, and we find many molluscs and other animals of marine +origin in the waters of these rivers far above tidal influence. +Conditions are unfavourable in the rivers themselves for the development +and multiplication of organisms of many groups, chiefly because of the +enormous amount of silt held in suspension in the water and constantly +being deposited on the bottom, and a much richer fauna exists in ponds +and lakes in the neighbourhood of the rivers and estuaries than in +running water. I have only found three species of polyzoa and three of +sponges in running water in India, and of these six species, five have +also been found in ponds or lakes. I have, on the other hand, found +three coelenterates in an estuary, and all three species are essentially +marine forms, but two have established themselves in ponds of brackish +water, one (the sea-anemone _Sagartia schilleriana_) undergoing in so +doing modifications of a very peculiar and interesting nature. It is not +uncommon for animals that have established themselves in pools of +brackish water to be found occasionally in ponds of fresh water; but I +have not been able to discover a single instance of an estuarine species +that is found in the latter and not in the former. + + [Footnote A: "L'origine des animaux d'eau douce," Bull. de + l'Acad. roy. de Belgique (Classe des Sciences), No. 12, + 1905, p. 724.] + +For these reasons I intended, as I have said, to include in this volume +descriptions of all the coelenterates and polyzoa known to occur in +pools of brackish water in the estuary of the Ganges and elsewhere in +India, but as my manuscript grew I began to realize that this would be +impossible without including also an amount of general introductory +matter not justified either by the scope of the volume or by special +knowledge on the part of its author. I have, however, given in the +introduction to each part a list of the species found in stagnant +brackish water with a few notes and references to descriptions. + + +BIOLOGICAL PECULIARITIES OF THE SPONGES, COELENTERATES, AND POLYZOA OF +FRESH WATER. + +There is often an external resemblance between the representatives of +the sponges, coelenterates, and polyzoa that causes them to be classed +together in popular phraseology as "zoophytes"; and this resemblance is +not merely a superficial one, for it is based on a similarity in habits +as well as of habitat, and is correlated with biological phenomena that +lie deeper than what are ordinarily called habits. These phenomena are +of peculiar interest with regard to difficult questions of nutrition and +reproduction that perhaps can only be solved by a close study of animals +living together in identical conditions and exhibiting, apparently in +consequence of so living, similar but by no means identical tendencies, +either anatomical or physiological, in certain directions. + +One of the most important problems on which the study of the sponges, +coelenterates, and polyzoa of stagnant water throws light is that of the +production of resting buds and similar reproductive bodies adapted to +withstand unfavourable conditions in a quiescent state and to respond to +the renewal of favourable conditions by a renewed growth and activity. + +Every autumn, in an English pond or lake, a crisis takes place in the +affairs of the less highly organized inhabitants, and preparations are +made to withstand the unfavourable conditions due directly or indirectly +to the low winter temperature of the water: the individual must perish +but the race may be preserved. At this season _Hydra_, which has been +reproducing its kind by means of buds throughout the summer, develops +eggs with a hard shell that will lie dormant in the mud until next +spring; the phylactolaematous polyzoa produce statoblasts, the +ctenostomatous polyzoa resting-buds ("hibernacula"), and the sponges +gemmules. Statoblasts, hibernacula, and gemmules are alike produced +asexually, but they resemble the eggs of _Hydra_ in being provided with +a hard, resistant shell, and in having the capacity to lie dormant until +favourable conditions return. + +In an Indian pond or lake a similar crisis takes place in the case of +most species, but it does not take place at the same time of year in the +case of all species. Unfortunately the phenomena of periodic +physiological change have been little studied in the freshwater fauna of +most parts of the country, and as yet we know very little indeed of the +biology of the Himalayan lakes and tarns, the conditions in which +resemble those to be found in similar masses of water in Europe much +more closely than they do those that occur in ponds and lakes in a +tropical plain. In Bengal, however, I have been able to devote +considerable attention to the subject, and can state definitely that +some species flourish chiefly in winter and enter the quiescent stage at +the beginning of the hot weather (that is to say about March), while +others reach their maximum development during the "rains" (July to +September) and as a rule die down during winter, which is the driest as +well as the coolest time of year. + +The following is a list of the forms that in Bengal are definitely known +to produce hard-shelled eggs, gemmules, resting-buds, or statoblasts +only or most profusely at the approach of the hot weather and to +flourish during winter:-- + + _Spongilla carteri._ + _Sponging alba._ + _Spongilla alba_ var. _bengalensis_. + _Spongilla crassissima._ + _Hydra vulgaris._ + _Victorella bengalensis._ + _Plumatella fruticosa._ + _Plumatella emarginata._ + _Plumatella javanica._ + +The following forms flourish mainly during the "rains":-- + + _Spongilla lacustris_ subsp. _reticulata_. + _Trochospongilla latouchiana._ + _Trochospongilla phillottiana._ + _Stolella indica._ + +The following flourish throughout the year:-- + + _Spongilla proliferens._ + _Hislopia lacustris._ + +It is particularly interesting to note that three of the species that +flourish in the mild winter of Bengal, namely _Hydra vulgaris_, +_Plumatella emarginata_, and _P. fruticosa_, are identical with species +that in Europe perish in winter. There is evidence, moreover, that the +statoblasts of the genus to which two of them belong burst more readily, +and thus give rise to new colonies, after being subjected to a +considerable amount of cold. In Bengal they only burst after being +subjected to the heat of the hot weather. Does extreme heat have a +similar effect on aquatic organisms as extreme cold? There is some +evidence that it has. + +The species that flourish in India during the rains are all forms which +habitually live near the surface or the edge of ponds or puddles, and +are therefore liable to undergo desiccation as soon as the rains cease +and the cold weather supervenes. + +The two species that flourish all the year round do not, properly +speaking, belong to one category, for whereas _Hislopia lacustris_ +produces no form of resting reproductive body but bears eggs and +spermatozoa at all seasons, _Spongilla proliferens_ is a short-lived +organism that undergoes a biological crisis every few weeks; that is to +say, it begins to develop gemmules as soon as it is fully formed, and +apparently dies down as soon as the gemmules have attained maturity. The +gemmules apparently lie dormant for some little time, but incessant +reproduction is carried on by means of external buds, a very rare method +of reproduction among the freshwater sponges. + +The facts just stated prove that considerable specific idiosyncrasy +exists as regards the biology of the sponges, hydroids, and polyzoa of +stagnant water in Bengal; but an even more striking instance of this +phenomenon is afforded by the sponges _Spongilla bombayensis_ and +_Corvospongilla lapidosa_ in Bombay. These two sponges resemble one +another considerably as regards their mode of growth, and are found +together on the lower surface of stones. In the month of November, +however, _C. lapidosa_ is in full vegetative vigour, while _C. +bombayensis_, in absolutely identical conditions, is already reduced to +a mass of gemmules, having flourished during the "rains." It is thus +clear that the effect of environment is not identical in different +species. This is more evident as regards the groups of animals under +consideration in India (and therefore probably in other tropical +countries) than it is in Europe. The subject is one well worthy of study +elsewhere than in India, for it is significant that specimens of _S. +bombayensis_ taken in November in S. Africa were in a state of activity, +thus contrasting strongly with specimens taken at the same time of year +(though not at the same season from a climatic point of view) in the +Bombay Presidency. + + +GEOGRAPHICAL DISTRIBUTION OF THE INDIAN SPECIES. + +The geographical distribution of the lower invertebrates of fresh and of +stagnant water is often an extremely wide one, probably because the +individual of many species exists at certain seasons or in certain +circumstances in a form that is not only resistant to unfavourable +environment, but also eminently capable of being transported by wind or +currents. We therefore find that some genera and even species are +practically cosmopolitan in their range, while others, so far as our +knowledge goes, appear to have an extraordinarily discontinuous +distribution. The latter phenomenon may be due solely to our ignorance +of the occurrence of obscure genera or species in localities in which +they have not been properly sought for, or it may have some real +significance as indicating that certain forms cannot always increase and +multiply even in those localities that appear most suitable for them. As +an example of universally distributed species we may take the European +polyzoa of the genus _Plumatella_ that occur in India, while of species +whose range is apparently discontinuous better examples could not be +found than the sponges _Trochospongilla pennsylvanica_ and _Spongilla +crateriformis_, both of which are only known from N. America, the +British Isles, and India. + +My geographical list of the species of sponges, coelenterates, and +polyzoa as yet found in fresh water in India is modelled on Col. +Alcock's recently published list of the freshwater crabs (Potamonidae) of +the Indian Empire[B]. I follow him in accepting, with slight +modifications of my own, Blanford's physiographical rather than his +zoogeographical regions, not because I think that the latter have been +or ought to be superseded so far as the vertebrates are concerned, but +rather because the limits of the geographical distribution of aquatic +invertebrates appear to depend on different factors from those that +affect terrestrial animals or even aquatic vertebrates. + + [Footnote B: Cat. Ind. Dec. Crust. Coll. Ind. Mus., part i, + fasc. ii (Potamonidae), 1910.] + +"Varieties" are ignored in this list, because they are not considered to +have a geographical significance. The parts of India that are least +known as regards the freshwater representatives of the groups under +consideration are the valley of the Indus, the lakes of Kashmir and +other parts of the Himalayas, the centre of the Peninsula, and the basin +of the Brahmaputra. Those that are best known are the districts round +Bombay, Calcutta, Madras and Bangalore, Travancore and Northern +Tenasserim. Little is known as regards Ceylon, and almost nothing as +regards the countries that surround the Indian Empire, a few species +only having been recorded from Yunnan and the Malay Peninsula, none from +Persia, Afghanistan, or Eastern Turkestan, and only one from Tibet. +Professor Max Weber's researches have, however, taught us something as +regards Sumatra and Java, while the results of various expeditions to +Tropical Africa are beginning to cast light on the lower invertebrates +of the great lakes in the centre of that continent and of the basin of +the Nile. + +It is not known to what altitude the three groups range in the Himalayas +and the hills of Southern India. No sponge has been found in Indian +territory at an altitude higher than that of Bhim Tal in Kumaon (4,500 +feet), and _Hydra_ is only known from the plains; but a variety of _H. +oligactis_ was taken by Capt. F. H. Stewart in Tibet at an altitude of +about 15,000 feet. _Plumatella diffusa_ flourishes at Gangtok in Sikhim +(6,100 feet), and I have found statoblasts of _P. fruticosa_ in the +neighbourhood of Simla on the surface of a pond situated at an altitude +of about 8,000 feet; Mr. R. Kirkpatrick obtained specimens of the genus +in the Botanical Gardens at Darjiling (6,900 feet), and two species have +been found at Kurseong (4,500-5,000 feet) in the same district. + + +GEOGRAPHICAL LIST OF THE FRESHWATER SPONGES, HYDROIDS, AND POLYZOA OF +INDIA, BURMA, AND CEYLON. + +[A * indicates that a species or subspecies has only been found in one +physiographical region or subregion so far as the Indian Empire is +concerned; a ! that the species has also been found in Europe, a $ in +North America, a + in Africa, and a @ in the Malay Archipelago.] + +1. Western Frontier Territory[C]. + +(Baluchistan, the Punjab, and the N.W. Frontier Province.) + + [Footnote C: I include Baluchistan in this territory largely + for climatic reasons.] + + SPONGES:-- + 1. _Spongilla_ (_Eunapius_) _carteri_!@ (Lahore). + + HYDROIDS:-- + 1. _Hydra oligactis_!$ (Lahore). + + POLYZOA:-- + 1. _Plumatella fruticosa_!$ (Lahore). + 2. _Plumatella diffusa_!$ (Lahore). + + +2. Western Himalayan Territory. + +(Himalayas from Hazara eastwards as far as Nepal.) + + SPONGES:-- + 1. _Spongilla_ (_Eunapius_) _carteri_!@ (Bhim Tal). + 2. _Ephydatia meyeni_@ (Bhim Tal). + + HYDROIDS:--None known (_Hydra oligactis_ recorded from Tibet). + + POLYZOA:-- + 1. _Plumatella allmani_! (Bhim Tal). + 2. _Plumatella fruticosa_!$ (Simla). + 3. _Lophopodella carteri_+ (Bhim Tal). + + +3. North-Eastern Frontier Territory. + +(Sikhim, Darjiling and Bhutan, and the Lower Brahmaputra +Drainage-System.) + + SPONGES:-- + _Spongilla proliferens_@ (Assam). + + HYDROIDS:--None known. + + POLYZOA:-- + 1. _Plumatella fruticosa_! (Kurseong and Assam). + 2. _Plumatella diffusa_!$ (Sikhim). + 3. _Plumatella javanica_@ (Kurseong). + + +4. Burma Territory. + +(Upper Burma, Arrakan, Pegu, Tenasserim.) + + SPONGES:-- + 1. _Spongilla_ (_Euspongilla_) _proliferens_@ (Upper Burma, Pegu). + 2. _Spongilla_ (_Euspongilla_) _crateriformis_!$ (Tenasserim). + 3. _Spongilla_ (_Eunapius_) _carteri_!@ (Upper Burma, Pegu, + Tenasserim). + 4. _Trochospongilla latouchiana_ (Tenasserim). + 5. _Trochospongilla phillottiana_ (Tenasserim). + 6. _Tubella vesparioides_* (Tenasserim). + 7. _Corvospongilla burmanica_* (Pegu). + + HYDROIDS:-- + 1. _Hydra vulgaris_!$ (Upper Burma and Tenasserim). + + POLYZOA:-- + 1. _Plumatella emarginata_!$ (Pegu, Upper Burma). + 2. _Plumatella allmani_! (Tenasserim). + 3. _Pectinatella burmanica_ (Tenasserim). + 4. _Hislopia lacustris_ (Pegu). + + +5 _a._ Peninsular Province--Main Area. + +(The Peninsula east of the Western Ghats.) + + SPONGES:-- + 1. _Spongilla_ (_Euspongilla_) _lacustris_ subsp. _reticulata_ + (Orissa, Madras). + 2. _Spongilla_ (_Euspongilla_) _proliferens_@ (Madras). + 3. _Spongilla_ (_Euspongilla_) _alba_+ (N. Madras, Orissa, Hyderabad). + 4. _Spongilla_ (_Euspongilla_) _hemephydatia_* (Orissa). + 5. _Spongilla_ (_Euspongilla_) _crateriformis_!$. + 6. _Spongilla_ (_Eunapius_) _carteri_!@. + 7. _Spongilla_ (_Eunapius_) _gemina_* (Bangalore). + 8. _Spongilla_ (_Stratospongilla_) _bombayensis_+ (Mysore). + 9. _Dosilia plumosa_ (N. Madras). + + HYDROIDS:-- + 1. _Hydra vulgaris_!$. + + POLYZOA:-- + 1. _Plumatella fruticosa_! (Madras, Bangalore). + 2. _Lophopus_ (?_Lophopodella_), sp. (Madras). + 3. _Pectinatella burmanica_ (Orissa). + 4. _Victorella bengalensis_ (Madras). + 5. _Hislopia lacustris_ (Nagpur). + + +5b. Peninsular Province--Malabar Zone. + +(Western Ghats from Tapti R. to Cape Comorin and eastwards +to the sea.) + + SPONGES:-- + 1. _Spongilla_ (_Euspongilla_) _lacustris_ subsp. _reticulata_ + (W. Ghats). + 2. _Spongilla_ (_Euspongilla_) _proliferens_@ (Cochin). + 3. _Spongilla_ (_Euspongilla_) _alba_+. + 4. _Spongilla_ (_Euspongilla_) _cinerea_*. + 5. _Spongilla_ (_Euspongilla_) _travancorica_* (Travancore). + 6. _Spongilla_ (_Euspongilla_) _crateriformis_!$ (Cochin). + 7. _Spongilla_ (_Eunapius_) _carteri_!@. + 8. _Spongilla_ (_Stratospongilla_) _indica_* (W. Ghats). + 9. _Spongilla _ (_Stratospongilla_) _bombayensis_+ (Bombay, W. Ghats). + 10. _Spongilla_ (_Stratospongilla_) _ultima_* (Travancore). + 11. _Pectispongilla aurea_* (Travancore, Cochin). + 12. _Ephydatia meyeni_@ (Bombay, Travancore). + 13. _Dosilia plumosa_ (Bombay). + 14. _Trochospongilla pennsylvanica_*!$ (Travancore). + 15. _Corvospongilla lapidosa_* (W. Ghats). + + HYDROIDS:--None recorded. + + POLYZOA:-- + 1. _Fredericella indica_* (W. Ghats and Travancore). + 2. _Plumatella fruticosa_! (Bombay). + 3. _Plumatella javanica_@ (Travancore). + 4. _Plumatella tanganyikae_*+ (W. Ghats). + 5. _Lophopodella carteri_+ (Bombay, W. Ghats). + + +6. Indo-Gangetic Plain. + +(From Sind to the Brahmaputra.) + + SPONGES:-- + 1. _Spongilla_ (_Euspongilla_) _lacustris_ subsp. _reticulata_ + (Gangetic delta). + 2. _Spongilla_ (_Euspongilla_) _proliferens_@ (Lower Bengal, etc.). + 3. _Spongilla_ (_Euspongilla_) _alba_+ (Lower Bengal). + 4. _Spongilla_ (_Euspongilla_) _crateriformis_!$. + 5. _Spongilla_ (_Eunapius_) _carteri_!@ (Lower Bengal, etc.). + 6. _Spongilla_ (_Eunapius_) _fragilis_ subsp. _calcuttana_* (Lower + Bengal). + 7. _Spongilla_ (_Eunapius_) _crassissima_ (Bengal). + 8. _Ephydatia meyeni_@ (Lower Bengal). + 9. _Trochospongilla latouchiana_ (Lower Bengal). + 10. _Trochospongilla phillottiana_ (Lower Bengal). + + HYDROIDS:-- + 1. _Hydra vulgaris_!$. + + POLYZOA:-- + 1. _Plumatella fruticosa_!. + 2. _Plumatella emarginata_!$. + 3. _Plumatella javanica_@ (Lower Bengal). + 4. _Plumatella diffusa_!$. + 5. _Plumatella allmani_!. + 6. _Plumatella punctata_!$ (Lower Bengal). + 7. _Stolella indica_* (Lower Bengal, United Provinces). + 8. _Victorella bengalensis_ (Lower Bengal). + 9. _Hislopia lacustris_ (United Provinces, N. Bengal). + 9a. _Hislopia lacustris_ subsp. _moniliformis_* (Lower Bengal). + + +7. Ceylon. + + SPONGES:-- + 1. _Spongilla_ (_Euspongilla_) _proliferens_@. + 2. _Spongilla_ (_Eunapius_) _carteri_!@. + + HYDROIDS:-- + 1. _Hydra vulgaris_!$. + + POLYZOA:-- + 1. ? _Plumatella emarginata_!$. + 2. _Pectinatella burmanica._ + +The most striking feature of this list is the evidence it affords as to +the distinct character of the fauna of the Malabar Zone, a feature that +is also remarkably clear as regards the Potamonidae, one genus of which +(_Gecarcinucus_) is peculiar, so far as India is concerned, to that +zone. As regards the sponges we may note the occurrence of no less than +three species of the subgenus _Stratospongilla_, which has not been +found elsewhere in India except on one occasion in Mysore, and of a +species of the genus _Corvospongilla_, which is unknown from the rest of +Peninsular India and from the Himalayas. The genus _Pectispongilla_ is +only known from the Malabar Zone. Among the polyzoa the genus +_Fredericella_[D] appears to be confined, so far as the Indian and +Burmese fauna is concerned, to the Malabar Zone, and the same is true as +regards the group of species to which _Plumatella tanganyikae_, an +African form, belongs. + + [Footnote D: Mr. S. W. Kemp recently obtained at Mangaldai, + near the Bhutan frontier of Assam, a single specimen of what + may be a species of _Fredericella_.] + +A further examination of the list of Malabar species and a consideration +of allied forms shows that the majority of the forms restricted to the +Malabar Zone are either African or else closely allied to African forms. +The genus _Corvospongilla_, except for one Burmese species, is otherwise +peculiar to Tropical Africa; while _Stratospongilla_, although not +confined to Africa, is more prolific in species in that continent than +in any other. _Spongilla (Stratospongilla) bombayensis_ has only been +found in Bombay, the Western Ghats, Mysore, and Natal, and _Plumatella +tanganyikae_ only in the Western Ghats and Central Africa. The genus +_Fredericella_ (which also occurs in Europe, N. America, and Australia) +is apparently of wide distribution in Africa, while _Lophopodella_ +(which in India is not confined to the Malabar Zone) is, except for a +Japanese race of the Indian species, restricted outside India, so far as +we know, to East Africa. + +A less definite relationship between the sponges and polyzoa of the +Malabar Zone and those of countries to the east of India is suggested by +the following facts:-- + + (1) The occurrence of the genus _Corvospongilla_ in Burma; + + (2) the occurrence of the subgenus _Stratospongilla_ in + Sumatra, China, and the Philippines; + + (3) the occurrence of a race of _Lophopodella carteri_ in + Japan; + + (4) the occurrence of a species allied to _Plumatella + tanganyikae_ in the Philippines. + +It will be noted that in each of these instances the relationship +extends to Africa as well as to the Eastern countries, and is more +marked in the former direction. The species of _Stratospongilla_, +moreover, that occurs in Sumatra (_S. sumatrensis_) also occurs in +Africa, while those that have been found in China and the Philippines +are aberrant forms. + +At first sight it might appear that these extra-Indian relationships +might be explained by supposing that gemmules and statoblasts were +brought to the Malabar Coast from Africa by the aerial currents of the +monsoon or by marine currents and carried from India eastwards by the +same agency, this agency being insufficient to transport them to the +interior and the eastern parts of the Peninsula. The work of La +Touche[E] on wind-borne foraminifera in Rajputana is very suggestive in +this direction; but that the peculiar sponge and polyzoon fauna of +Malabar is due to the agency either of wind or of marine currents may be +denied with confidence, for it is a striking fact that most of the +characteristic genera and subgenera of the Zone have resting +reproductive bodies that are either fixed to solid objects or else are +devoid of special apparatus to render them light. The former is the case +as regards all species of _Corvospongilla_ and all Indian and most other +species of _Stratospongilla_, the gemmules of which not only are +unusually heavy but also adhere firmly; while the statoblasts of +_Fredericella_ have no trace of the air-cells that render the free +statoblasts of all other genera of phylactolaematous polyzoa peculiarly +light and therefore peculiarly liable to be transported by wind. + + [Footnote E: See Mem. Geol. Surv. Ind. XXXV (1), p. 39 + (1902).] + +A true geographical or geological explanation must therefore be sought +for the relationship between the sponges and polyzoa of Malabar, of +Africa, and of the Eastern countries--a relationship that is well known +to exist as regards other groups of animals. No more satisfactory +explanation has as yet been put forward than that of a former land +connection between Africa and the Malaysia through Malabar at a period +(probably late Cretaceous) when the Western Ghats were much higher than +they now are[F]. + + [Footnote F: See Ortmann, "The Geographical Distribution of + Freshwater Decapods and its bearing upon Ancient Geography," + Proc. Amer. Phil. Soc. xli, p. 380, fig. 6 (1902); also + Suess, "The Face of the Earth" (English ed.) i, p. 416 + (1904).] + +There is little to be said as regards the distribution of the sponges, +hydroids, and polyzoa of fresh water in other parts of India. It may be +noted, however, that the species known from the Punjab are all widely +distributed Palaearctic forms, and that the genus _Stolella_ is +apparently confined to the Indo-Gangetic Plain. Two species of sponge +are peculiar to Lower Burma, one of them (_Corvospongilla burmanica_) +representing the geographical alliance already discussed as regards the +Malabar Zone, the other (_Tubella vesparioides_) closely related to a +Malaysian species (_T. vesparium_ from Borneo) and perhaps representing +the northern limit of the Malaysian element well known in the fauna of +Lower Burma. Of the sponges and polyzoa of Ceylon we know as yet too +little to make it profitable to discuss their affinities. All that have +as yet been discovered occur also in Peninsular India; nor do they +afford any evidence of a connection with the Malabar Zone. + +The question of the geographical range of the sponges, hydroids, and +polyzoa of brackish water may be considered briefly, for it is of +importance in considering that of those which are confined to fresh +water. Some of these species from brackish water (e. g., _Membranipora +lacroixii_) are identical with others (e. g., _Victorella bengalensis_ +and _Bowerbankia caudata_ subsp. _bengalensis_) closely related to +European forms. Others again (e. g., _Loxosomatoides colonialis_ and +_Sagartia schilleriana_) are known as yet from the Ganges delta only. In +our ignorance of the Indian representatives of the groups to which they +belong, it is impossible to assert that their distribution is actually +so restricted as it seems. + + +SOME SPECIAL LOCALITIES. + +In order to avoid constant repetition as regards the conditions that +prevail at the places most frequently mentioned in this volume, a few +details as regards them may be conveniently stated here. + +_Lower Bengal._ + +CALCUTTA is situated on the River Hughli at a point about 90 miles from +the open sea. The water of the river is practically fresh, but is +strongly affected by the tides; it is always turbid and of a brownish +colour. The river, however, is not a good collecting ground for sponges, +coelenterates, and polyzoa, and none of the species described in this +volume have been obtained from it. It is in the Calcutta "tanks" that +most of my investigations have been made. These tanks are ponds, mostly +of artificial origin, very numerous, of varying size but never very +large or deep. Most of them contain few solid objects to which sedentary +organisms can fix themselves, and such ponds are of course poor in +sponges and polyzoa. Others, however, support a prolific growth of weeds +such as _Pistia stratiotes_, _Lemna_, and _Limnanthemum_, and a few have +brickwork or artificial stonework at their sides. In those parts of the +town that approach the Salt Lakes (large lagoons and swamps of brackish +water connected with the sea by the Mutlah River) the water of the ponds +is slightly brackish and permits few plants except algae to flourish. Few +of the bigger tanks ever dry up. The best of the tanks from the +sponge-collector's point of view, so far as I have been able to +discover, is the one in the compound of the Indian Museum. It enjoys all +the advantages of light and shade, solid supports, prolific aquatic +vegetation, considerable depth, and the vicinity of human dwellings that +seem to be favourable to the growth of sponges, no less than nine +species of which, representing three genera and two subgenera, grow +abundantly in it. _Hydra_ also flourishes in this pond, but for some +reasons there are few polyzoa. The phylactolaematous species of the +latter group, however, are extraordinarily abundant in one of the tanks +in the Zoological Gardens at Alipore. In this tank, which unlike the +Museum tank is directly connected with the river, no less than six +species and varieties of the genus _Plumatella_ have been found growing +together on sticks, floating seeds, and water-plants. Except _Hislopia_, +which is common on _Vallisneria_ in one tank on the Maidan (opposite the +Bengal Club), the ctenostomes of stagnant water are only found in the +tanks near the Salt Lakes. + +PORT CANNING is situated on the Mutlah River about 30 miles from +Calcutta and about 60 from the open sea. The Mutlah is really a tidal +creek rather than a river, in spite of the fact that it runs for a +considerable number of miles, and its waters are distinctly brackish. +Water taken from the edge at Port Canning in March was found to contain +25.46 per thousand of saline residue. The interesting feature of Port +Canning, however, is from a zoological point of view not the Mutlah but +certain ponds of brackish water now completely separated from it, except +occasionally when the river is in flood, but communicating regularly +with it in the memory of living persons. These ponds, which were +apparently not in existence in 1855, have on an average an area of about +half an acre each, and were evidently formed by the excavation of earth +for the construction of an embankment along the Mutlah. They are very +shallow and lie exposed to the sun. The salinity differs considerably in +different ponds, although the fauna seems to be identical; the water of +one pond was found to contain 22.88 per thousand of saline residue in +May, 20.22 per thousand in March, and 12.13 in December. A second pond +in the neighbourhood of the first and apparently similar to it in every +way contained only 9.82 per thousand in July, after the rains had +broken. The fauna of these ponds includes not only a freshwater sponge +(_Spongilla alba_ var. _bengalensis_) but also many aquatic insects +(_e. g._, larvae of mosquitos and of _Chironomus_ and several species of +beetles and Rhynchota); while on the other hand essentially marine +coelenterates (_Irene ceylonensis_, etc.) and worms (_e. g._, the +gephyrean _Physcosoma lurco_[G]) form a part of it, together with forms +of intermediate habitat such as _Bowerbankia caudata_ subsp. +_bengalensis_, _Victorella bengalensis_, and several fish and crustacea +common in brackish water. + + [Footnote G: I am indebted to Mr. W. F. Lanchester for the + identification of this species.] + +_Orissa._ + +Orissa may be described in general terms as consisting of the coastal +area of Bengal south of the Gangetic delta. It extends in inland, +however, for a considerable distance and includes hilly tracts. There is +no geographical boundary between it and the north-eastern part of the +Madras Presidency or the eastern part of the Central Provinces. + +CHILKA LAKE.--This marine lake is a shallow lagoon measuring about 40 +miles in length and 10 miles in breadth, and formed in geologically +recent times by the growth of a narrow sand-bank across the mouth of a +wide bay. At its northern end it communicates with the sea by a narrow +channel, and throughout its length it is strongly affected by the tides. +At its south end, which is actually situated in the Ganjam district of +Madras, the water is distinctly brackish and is said to be nearly fresh +at certain times of year. At this end there are numerous small +artificial pools of brackish water somewhat resembling those of Port +Canning as regards their fauna. + +SUR (or SAR) LAKE.--A shallow, freshwater lake of very variable size +situated a few miles north of Puri on the Orissa coast. In origin it +probably resembled the Chilka Lake, but it is now separated from the sea +by about 3 miles of barren sand dunes, among which numerous little pools +of rain-water are formed during the rains. These dry up completely in +winter, and even the lake itself is said sometimes almost to disappear, +although when it is full it is several miles in length. The fauna is +essentially a freshwater one, but includes certain Mysidae and other +crustacea usually found in brackish water. + +_Bombay Presidency._ + +BOMBAY.--The town of Bombay, built on an island near the mainland, is +situated close to swamps and creeks of brackish water not unlike those +that surround Calcutta. Its "tanks," however, differ from those of +Calcutta in having rocky bottoms and, in many cases, in drying up +completely in the hot weather. Of the fauna of the swamps extremely +little is known, but so far as the sponges and polyzoa of the tanks are +concerned the work undertaken by Carter was probably exhaustive. + +IGATPURI.--Igatpuri is situated at an altitude of about 2000 feet, 60 +miles north-east of Bombay. Above the town there is a lake of several +square miles in area whence the water-supply of several stations in the +neighbourhood is obtained. The water is therefore kept free from +contamination. The bottom is composed of small stones and slopes +gradually up at the edges. During the dry weather its level sinks +considerably. Several interesting sponges and polyzoa have been found in +this lake, most of them also occurring in a small pond in the +neighbourhood in which clothes are washed and the water is often full of +soap-suds. + +_Southern India._ + +MADRAS.--The city of Madras is built by the sea, straggling over a large +area of the sandy soil characteristic of the greater part of the east +coast of India. In wet weather this soil retains many temporary pools of +rain-water, and there are numerous permanent tanks of no great size in +the neighbourhood of the town. The so-called Cooum River, which flows +through the town, is little more than a tidal creek, resembling the +Mutlah River of Lower Bengal on a much smaller scale. The sponges and +polyzoa as yet found in the environs of Madras are identical with those +found in the environs of Calcutta. + +BANGALORE.--Bangalore (Mysore State) is situated near the centre of the +Madras Presidency on a plateau about 3000 feet above sea-level. The +surrounding country is formed of laterite rock which decomposes readily +and forms a fine reddish silt in the tanks. These tanks are numerous, +often of large size, and as a rule at least partly of artificial origin. +Their water supports few phanerogamic plants and is, as my friend Dr. +Morris Travers informs me, remarkably free from salts in solution. The +sponge fauna of the neighbourhood of Bangalore appears to be +intermediate between that of Madras and that of Travancore. + +THE BACKWATERS OF COCHIN AND TRAVANCORE.--The "backwaters" of Cochin and +Travancore were originally a series of shallow lagoons stretching along +the coast of the southern part of the west coast of India for a distance +of considerably over a hundred miles. They have now been joined together +by means of canals and tunnels to form a tidal waterway, which +communicates at many points directly with the sea. The salinity of the +water differs greatly at different places and in different seasons, and +at some places there is an arrangement to keep out sea-water while the +rice-fields are being irrigated. The fauna is mainly marine, but in the +less saline parts of the canals and lakes many freshwater species are +found. + +_Shasthancottah._--There are two villages of this name, one situated on +the backwater near Quilon (coast of Travancore), the other about three +miles inland on a large freshwater lake. This lake, which does not +communicate with the backwater, occupies a narrow winding rift several +miles in length at a considerable depth below the surrounding country. +Its bottom is muddy and it contains few water-plants, although in some +places the water-plants that do exist are matted together to form +floating islands on which trees and bushes grow. The fauna, at any rate +as regards mollusca and microscopic organisms, is remarkably poor, but +two species of polyzoa (_Fredericella indica_ and _Plumatella +fruticosa_) and one of sponge (_Trochospongilla pennsylvanica_) grow in +considerable abundance although not in great luxuriance. + +_The Himalayas._ + +BHIM TAL[H] is a lake situated at an altitude of 4500 feet in that part +of the Western Himalayas known as Kumaon, near the plains. It has a +superficial area of several square miles, and is deep in the middle. Its +bottom and banks are for the most part muddy. Little is known of its +fauna, but two polyzoa (_Plumatella allmani_ and _Lophopodella carteri_) +and the gemmules of two sponges (_Spongilla carteri_ and _Ephydatia +meyeni_) have been found in it. + + [Footnote H: The fauna of this lake and of others in the + neighbourhood has recently been investigated by Mr. S. W. + Kemp. See the addenda at the end of this volume.--_June + 1911._] + + * * * * * + +NOMENCLATURE AND TERMINOLOGY. + +The subject of nomenclature may be considered under four heads:--(I.) +the general terminology of the various kinds of groups of individuals +into which organisms must be divided; (II.) the general nomenclature of +specimens belonging to particular categories, such as types, co-types, +etc.; (III.) the nomenclature that depends on such questions as that of +"priority"; and (IV.) the special terminology peculiar to the different +groups. The special terminology peculiar to the different groups is +dealt with in the separate introductions to each of the three parts of +this volume. + + +(I.) + +No group of animals offers greater difficulty than the sponges, +hydroids, and polyzoa (and especially the freshwater representatives of +these three groups) as regards the question "What is a species?" and the +kindred questions, "What is a subspecies?" "What is a variety?" and +"What is a phase?" Genera can often be left to look after themselves, +but the specific and kindred questions are answered in so many different +ways, if they are even considered, by different systematists, especially +as regards the groups described in this volume, that I feel it necessary +to state concisely my own answers to these questions, not for the +guidance of other zoologists but merely to render intelligible the +system of classification here adopted. The following definitions should +therefore be considered in estimating the value of "species," etc., +referred to in the following pages. + +_Species._--A group of individuals differing in constant characters of a +definite nature and of systematic[I] importance from all others in the +same genus. + + [Footnote I: "What characters are of systematic importance?" + is a question to which different answers must be given in + the case of different groups.] + +_Subspecies._--An isolated or local race, the individuals of which +differ from others included in the same species in characters that are +constant but either somewhat indefinite or else of little systematic +importance. + +_Variety._--A group of individuals not isolated geographically from +others of the same species but nevertheless exhibiting slight, not +altogether constant, or indefinite differences from the typical form of +the species (_i. e._, the form first described). + +_Phase._--A peculiar form assumed by the individuals of a species which +are exposed to peculiarities in environment and differ from normal +individuals as a direct result. + +There are cases in which imperfection of information renders it +difficult or impossible to distinguish between a variety and a +subspecies. In such cases it is best to call the form a variety, for +this term does not imply any special knowledge as regards its +distribution or the conditions in which it is found. + +I use the term "form" in a general sense of which the meaning or +meanings are clear without explanation. + + +(II.) + +The question of type specimens must be considered briefly. There are two +schools of systematists, those who assert that one specimen and one only +must be the type of a species, and those who are willing to accept +several specimens as types. From the theoretical point of view it seems +impossible to set up any one individual as the ideal type of a species, +but those who possess collections or are in charge of museums prefer, +with the natural instinct of the collector, to have a definite single +type (of which no one else can possibly possess a duplicate) in their +possession or care, and there is always the difficulty that a zoologist +in describing a species, if he recognizes more than one type, may +include as types specimens that really belong to more than one species. +These difficulties are met by some zoologists by the recognition of +several specimens as paratypes, all of equal value; but this, after all, +is merely a terminological means of escaping from the difficulty, +calculated to salve the conscience of a collector who feels unwilling to +give up the unique type of a species represented by other specimens in +his collection. The difficulty as regards the confounding of specimens +of two or more species as the types of one can always be adjusted if the +author who discovers the mistake redescribes one of the species under +the original name and regards the specimen that agrees with his +description as the type, at the same time describing a new species with +another of the specimens as its type. Personally I always desire to +regard the whole material that forms the basis of an original +description of a species as the type, but museum rules often render this +impossible, and the best that can be done is to pick out one specimen +that seems particularly characteristic and to call it the type, the rest +of the material being termed co-types. A peculiar difficulty arises, +however, as regards many of the sponges, coelenterates, and polyzoa, +owing to the fact that they are often either compound animals, each +specimen consisting of more than one individual, or are easily divisible +into equivalent fragments. If the single type theory were driven to its +logical conclusion, it would be necessary to select one particular polyp +in a hydroid colony, or even the part of a sponge that surrounded a +particular osculum as the type of the species to which the hydroid or +the sponge belonged. Either by accident or by design specimens of +Spongillidae, especially if kept dry, are usually broken into several +pieces. There is, as a matter of fact, no reason to attribute the +peculiarly sacrosanct nature of a type to one piece more than another. +In such cases the biggest piece may be called the type, while the +smaller pieces may be designated by the term "schizotype." + +The more precise definition of such terms as topotype, genotype, _et +hujus generis omnis_ is nowadays a science (or at any rate a form of +technical industry) by itself and need not be discussed here. + + +(III.) + +In 1908 an influential committee of British zoologists drew up a +strenuous protest against the unearthing of obsolete zoological names +(see 'Nature,' Aug. 1908, p. 395). To no group does this protest apply +with greater force than to the three discussed in this volume. It is +difficult, however, to adopt any one work as a standard of nomenclature +for the whole of any one of them. As regards the Spongillidae it is +impossible to accept any monograph earlier than Potts's "Fresh-Water +Sponges" (P. Ac. Philad., 1887), for Bowerbank's and Carter's earlier +monographs contained descriptions of comparatively few species. Even +Potts's monograph I have been unable to follow without divergence, for +it seems to me necessary to recognize several genera and subgenera that +he ignored. The freshwater polyzoa, however, were dealt with in so +comprehensive a manner by Allman in his "Fresh-Water Polyzoa" (London, +1856) that no difficulty is experienced in ignoring, so far as +nomenclature is concerned, any earlier work on the group; while as +regards other divisions of the polyzoa I have followed Hincks's "British +Marine Polyzoa" (1880), so far as recent researches permit. In most +cases I have not attempted to work out an elaborate synonymy of species +described earlier than the publication of the works just cited, for to +do so is a mere waste of time in the case of animals that call for a +most precise definition of species and genera and yet were often +described, so far as they were known earlier than the dates in question, +in quite general terms. I have been confirmed in adopting this course by +the fact that few of the types of the earlier species are now in +existence, and that a large proportion of the Indian forms have only +been described within the last few years. + + +MATERIAL. + +The descriptions in this volume are based on specimens in the collection +of the Indian Museum, the Trustees of which, by the liberal manner in +which they have permitted me to travel in India and Burma on behalf of +the Museum, have made it possible not only to obtain material for study +and exchange but also to observe the different species in their natural +environment. This does not mean to say that specimens from other +collections have been ignored, for many institutions and individuals +have met us generously in the matter of gifts and exchanges, and our +collection now includes specimens of all the Indian forms, named in +nearly all cases by the author of the species, except in those of +species described long ago of which no authentic original specimens can +now be traced. Pieces of the types of all of the Indian Spongillidae +described by Carter have been obtained from the British Museum through +the kind offices of Mr. R. Kirkpatrick. The Smithsonian Institution has +sent us from the collection of the United States National Museum +specimens named by Potts, and the Berlin Museum specimens named by +Weltner, while to the Imperial Academy of Sciences of St. Petersburg we +owe many unnamed but interesting sponges. Dr. K. Kraepelin and Dr. W. +Michaelsen have presented us with specimens of most of the species and +varieties of freshwater polyzoa described by the former in his great +monograph and elsewhere. We owe to Dr. S. F. Harmer, formerly of the +Cambridge University Museum and now Keeper in Zoology at the British +Museum, to Professor Max Weber of Amsterdam, Professor Oka of Tokyo, and +several other zoologists much valuable material. I would specially +mention the exquisite preparations presented by Mr. C. Rousselet. +Several naturalists in India have also done good service to the Museum +by presenting specimens of the three groups described in this volume, +especially Major H. J. Walton, I.M.S., Major J. Stephenson, I.M.S., Dr. +J. R. Henderson and Mr. G. Matthai of Madras, and Mr. R. Shunkara +Narayana Pillay of Trivandrum. + +The following list shows where the types of the various species, +subspecies, and varieties are preserved, so far as it has been possible +to trace them. I have included in this list the names of all species +that have been found in stagnant water, whether fresh or brackish, but +those of species not yet found in fresh water are enclosed in square +brackets. + ++-----------------------------------------------------------------------+ +| INDIAN SPONGILLIDAE. | +| | ++---------------------------------+----------------------+--------------+ +| NAME. | TYPE IN COLL. | MATERIAL | +| | | EXAMINED. | ++---------------------------------+----------------------+--------------+ +| _Spongilla lacustris_ subsp. | Ind. Mus. | Type. | +| _reticulata_ | | | ++---------------------------------+----------------------+--------------+ +| _Spongilla proliferens_ | " " | " | ++---------------------------------+----------------------+--------------+ +| _Spongilla alba_ | Brit. and Ind. Mus. | Schizotype. | ++---------------------------------+----------------------+--------------+ +| [_Spongilla alba_ var. | Ind. Mus. | Type | +| _bengalensis_] | | | ++---------------------------------+----------------------+--------------+ +| _Spongilla alba_ var. | Brit. Mus. | {Specimens | +| _cerebellata_ | | {compared | +| | | {with type. | ++---------------------------------+----------------------+--------------+ +| _Spongilla cinerea_ | Brit. and Ind. Mus. | Schizotype. | ++---------------------------------+----------------------+--------------+ +| [_Spongilla travancorica_] | Ind. Mus. | Type. | ++---------------------------------+----------------------+--------------+ +| _Spongilla hemephydatia_ | " " | " | ++---------------------------------+----------------------+--------------+ +| _Spongilla crateriformis_ | U.S. Nat. Mus. | Co-type. | ++---------------------------------+----------------------+--------------+ +| _Spongilla carteri_ | Brit. and Ind. Mus. | Schizotype. | ++---------------------------------+----------------------+--------------+ +| _Spongilla carteri_ var. | Ind. Mus. | Type. | +| _mollis_ | | | ++---------------------------------+----------------------+--------------+ +| _Spongilla carteri_ var. | " " | " | +| _cava_ | | | ++---------------------------------+----------------------+--------------+ +| _Spongilla carteri_ var. | " " | " | +| _lobosa_ | | | ++---------------------------------+----------------------+--------------+ +| _Spongilla fragilis_ subsp. | " " | " | +| _calcuttana_ | | | ++---------------------------------+----------------------+--------------+ +| _Spongilla fragilis_ subsp. | Amsterdam Mus. | Co-type. | +| _decipiens_ | | | ++---------------------------------+----------------------+--------------+ +| _Spongilla gemina_ | Ind. Mus. | Type. | ++---------------------------------+----------------------+--------------+ +| _Spongilla crassissima_ | " " | " | ++---------------------------------+----------------------+--------------+ +| _Spongilla crassissima_ var. | " " | " | +| _crassior_ | | | ++---------------------------------+----------------------+--------------+ +| _Spongilla bombayensis_ | Brit. and Ind. Mus. | Schizotype. | ++---------------------------------+----------------------+--------------+ +| _Spongilla indica_ | Ind. Mus. | Type. | ++---------------------------------+----------------------+--------------+ +| _Spongilla ultima_ | " " | " | ++---------------------------------+----------------------+--------------+ +| _Pectispongilla aurea_ | " " | " | ++---------------------------------+----------------------+--------------+ +| _Ephydatia meyeni_ | Brit. and Ind. Mus. | Schizotype. | ++---------------------------------+----------------------+--------------+ +| _Dosilia plumosa_ | " " " " | " | ++---------------------------------+----------------------+--------------+ +| _Trochospongilla latouchiana_ | Ind. Mus. | Type. | ++---------------------------------+----------------------+--------------+ +| _Trochospongilla phillottiana_ | " " | " | ++---------------------------------+----------------------+--------------+ +| _Trochospongilla pennsylvanica_ | U.S. Nat. Mus. | Co-type. | ++---------------------------------+----------------------+--------------+ +| _Tubella vesparioides_ | Ind. Mus. | Type. | ++---------------------------------+----------------------+--------------+ +| _Corvospongilla burmanica_ | Brit. and Ind. Mus. | Schizotype. | ++---------------------------------+----------------------+--------------+ +| _Corvospongilla lapidosa_ | Ind. Mus. | Type. | ++---------------------------------+----------------------+--------------+ +| INDIAN COELENTERATES OF STAGNANT WATER. | ++---------------------------------+----------------------+--------------+ +| HYDROZOA. | | | ++---------------------------------+----------------------+--------------+ +| _Hydra oligactis_ | Not in existence. | | ++---------------------------------+----------------------+--------------+ +| _Hydra vulgaris_ | " " | | ++---------------------------------+----------------------+--------------+ +| [_Syncoryne filamentata_] | Ind. Mus. | Type. | ++---------------------------------+----------------------+--------------+ +| [_Bimeria vestita_] | ? Not in existence. | | ++---------------------------------+----------------------+--------------+ +| [_Irene ceylonensis_] | {Hydroid in Ind.} | Hydroid type | +| | {Mus., Medusa} | | +| | {in Brit. Mus.} | | ++---------------------------------+----------------------+--------------+ +| ACTINIARIA. | | | ++---------------------------------+----------------------+--------------+ +| [_Sagartia schilleriana_] | Ind. Mus. | Types. | ++---------------------------------+----------------------+--------------+ +| [_Sagartia schilleriana_ | " " | " | +| subsp. _exul_] | | | ++---------------------------------+----------------------+--------------+ +| INDIAN POLYZOA OF STAGNANT WATER. | ++---------------------------------+----------------------+--------------+ +| ENTOPROCTA. | | | ++---------------------------------+----------------------+--------------+ +| [_Loxosomatoides colonialis_] | Ind. Mus. | Types. | ++---------------------------------+----------------------+--------------+ +| ECTOPROCTA CHEILOSTOMATA. | | | ++---------------------------------+----------------------+--------------+ +| [_Membranipora lacroixii_] | ? Paris Mus. | | ++---------------------------------+----------------------+--------------+ +| [_Membranipora bengalensis_] | Ind. Mus. | Types. | ++---------------------------------+----------------------+--------------+ +| ECTOPROCTA STENOSTOMATA. | | | ++---------------------------------+----------------------+--------------+ +| [_Bowerbankia caudata_ subsp. | Ind. Mus. | Types. | +| _bengalensis_] | | | ++---------------------------------+----------------------+--------------+ +| _Victorella bengalensis_ | " " | " | ++---------------------------------+----------------------+--------------+ +| _Hislopia lacustris_ | ? Not in existence. | | ++---------------------------------+----------------------+--------------+ +| _Hislopia lacustris_ subsp. | Ind. Mus. | " | +| _moniliformis_ | | | ++---------------------------------+----------------------+--------------+ +| ECTOPROCTA PHYLACTOLAEMATA. | | | ++---------------------------------+----------------------+--------------+ +| _Fredericella indica_ | Ind. Mus. | Type. | ++---------------------------------+----------------------+--------------+ +| _Plumatella fruticosa_ | Not in existence. | | ++---------------------------------+----------------------+--------------+ +| _Plumatella diffusa_ |?Philadelphia Acad.[J]| | ++---------------------------------+----------------------+--------------+ +| _Plumatella allmani_ | Not in existence. | | ++---------------------------------+----------------------+--------------+ +| _Plumatella emarginata_ | " " | | ++---------------------------------+----------------------+--------------+ +| | {Hamburg and} | One of the | +| _Plumatella javanica_ | {Ind. Mus. } | types. | ++---------------------------------+----------------------+--------------+ +| | {Brit. and Ind.} | One of the | +| _Plumatella tanganyikae_ | {Mus. } | types. | ++---------------------------------+----------------------+--------------+ +| _Stolella indica_ | Ind. Mus. | Type. | ++---------------------------------+----------------------+--------------+ +| _Lophopodella carteri_ | Brit. Mus. | " | ++---------------------------------+----------------------+--------------+ +| _Lophopodella carteri_ var. | Ind. Mus. | " | +| _himalayana_ | | | ++---------------------------------+----------------------+--------------+ +| _Pectinatella burmanica_ | Ind. Mus. | " | ++---------------------------------+----------------------+--------------+ + + [Footnote J: I have failed to obtain from the Philadelphia + Academy of Science a statement that the type of this species + is still in existence.] + + +The literature dealing with the various groups described in the volume +is discussed in the introductions to the three parts. Throughout the +volume I have, so far as possible, referred to works that can be +consulted in Calcutta in the libraries of the Indian Museum, the +Geological Survey of India, or the Asiatic Society of Bengal. The names +of works that are not to be found in India are marked with a *. The +rarity with which this mark occurs says much for the fortunate position +in which zoologists stationed in Calcutta find themselves as regards +zoological literature, for I do not think that anything essential has +been omitted. + +It remains for me to express my gratitude to those who have assisted me +in the preparation of this volume. The names of those who have +contributed specimens for examination have already been mentioned. I +have to thank the Trustees of the Indian Museum not only for their +liberal interpretation of my duties as an officer of the Museum but also +for the use of all the drawings and photographs and some of the blocks +from which this volume is illustrated. Several of the latter have +already been used in the "Records of the Indian Museum." From the Editor +of the "Fauna" I have received valuable suggestions, and I am indebted +to Dr. Weltner of the Berlin Museum for no less valuable references to +literature. Mr. F. H. Gravely, Assistant Superintendent in the Indian +Museum, has saved me from several errors by his criticism. + +The majority of the figures have been drawn by the draftsmen of the +Indian Museum, Babu Abhoya Charan Chowdhary, and of the Marine Survey of +India, Babu Shib Chandra Mondul, to both of whom I am much indebted for +their accuracy of delineation. + +No work dealing with the sponges of India would be complete without a +tribute to the memory of H. J. Carter, pioneer in the East of the study +of lower invertebrates, whose work persists as a guide and an +encouragement to all of us who are of the opinion that biological +research on Indian animals can only be undertaken in India, and that +even systematic zoological work can be carried out in that country with +success. I can only hope that this, the first volume in the official +Fauna of the Indian Empire to be written entirely in India, may prove +not unworthy of his example. + +Indian Museum, Calcutta Oct. 23rd, 1910. + + + + +PART I. + +FRESHWATER SPONGES + +(SPONGILLIDAE). + + + + +INTRODUCTION TO PART I. + + +I. + +THE PHYLUM PORIFERA. + +The phylum Porifera or Spongiae includes the simplest of the Metazoa or +multicellular animals. From the compound Protozoa its members are +distinguished by the fact that the cells of which they are composed +exhibit considerable differentiation both in structure and in function, +and are associated together in a definite manner, although they are not +combined to form organs and systems of organs as in the higher Metazoa. +Digestion, for instance, is performed in the sponges entirely by +individual cells, into the substance of which the food is taken, and the +products of digestion are handed on to other cells without the +intervention of an alimentary canal or a vascular system, while there is +no structure in any way comparable to the nervous system of more highly +organized animals. + +The simplest form of sponge, which is known as an olynthus, is a hollow +vase-like body fixed at one end to some solid object, and with an +opening called the osculum at the other. The walls are perforated by +small holes, the pores, from which the name Porifera is derived. + +Externally the surface is protected by a delicate membrane formed of +flattened cells and pierced by the pores, while the interior of the vase +is covered with curious cells characteristic of the sponges, and known +as choanocytes or collar-cells. They consist of minute oval or +pear-shaped bodies, one end of which is provided with a rim or collar of +apparently structureless membrane, while a flagellum or whip-like lash +projects from the centre of the surface surrounded by the collar. These +collar-cells are practically identical with those of which the Protozoa +known as Choanoflagellata consist; but it is only in the sponges[K] that +they are found constantly associated with other cells unlike themselves. + + [Footnote K: Except in "_Proterospongia_," an organism of + doubtful affinities but not a sponge. It consists of a mass + of jelly containing ordinary cells, with collar-cells + _outside_.] + +In addition to the collar-cells, which form what is called the gastral +layer, and the external membrane (the derma or dermal membrane), the +sponge contains cells of various kinds embedded in a structureless +gelatinous substance, through which they have the power of free +movement. Most of these cells have also the power of changing their form +in an "amoeboid" manner; that is to say, by projecting and withdrawing +from their margin mobile processes of a more or less finger-like form, +but unstable in shape or direction. The protoplasm of which some of the +cells are formed is granular, while that of others is clear and +translucent. Some cells, which (for the time being at any rate) do not +exhibit amoeboid movements, are glandular in function, while others +again give rise in various ways to the bodies by means of which the +sponge reproduces its kind. There is evidence, however, that any one +kind of cell, even those of the membrane and the gastral layer, can +change its function and its form in case of necessity. + +Most sponges possess a supporting framework or skeleton. In some it is +formed entirely of a horny substance called spongin (as in the +bath-sponge), in others it consists of spicules of inorganic matter +(either calcareous or siliceous) secreted by special cells, or of such +spicules bound together by spongin. Extraneous objects, such as +sand-grains, are frequently included in the skeleton. The spongin is +secreted like the spicules by special cells, but its chemical structure +is much more complicated than that of the spicules, and it is not +secreted (at any rate in most cases) in such a way as to form bodies of +a definite shape. In the so-called horny sponges it resembles the chitin +in which insects and other arthropods are clothed. + + * * * * * + +In no adult sponge do the collar-cells completely cover the whole of the +internal surface, the olynthus being a larval form, and by no means a +common larval form. It is only found in certain sponges with calcareous +spicules. As the structure of the sponge becomes more complicated the +collar-cells are tucked away into special pockets or chambers known as +ciliated chambers, and finally the approach to these chambers, both from +the external surface and from the inner or gastral cavity, takes the +form of narrow tubes or canals instead of mere pores. With further +complexity the simple internal cavity tends to disappear, and the sponge +proliferates in such a way that more than one osculum is formed. In the +class Demospongiae, to which the sponges described in this volume belong, +the whole system is extremely complicated. + +The skeleton of sponges, when it is not composed wholly of spongin, +consists of, or at any rate contains, spicules that have a definite +chemical composition and definite shapes in accordance with the class, +order, family, genus, and species of the sponge. Formerly sponges were +separated into calcareous, siliceous, and horny sponges by the nature of +their skeleton; and although the system of classification now adopted +has developed into a much more complex one and a few sponges are known +that have both calcareous and siliceous spicules, the question whether +the spicules are formed of salts of lime or of silica (strictly speaking +of opal) is very important. All Demospongiae that have spicules at all +have them of the latter substance, and the grade Monaxonida, in which +the freshwater sponges constitute the family Spongillidae, is +characterized by the possession of spicules that have typically the form +of a needle pointed at both ends. Although spicules of this simple form +may be absent in species that belong to the grade, the larger spicules, +which are called megascleres, have not normally more than one main axis +and are always more or less rod-like in outline. They are usually +arranged so as to form a reticulate skeleton. Frequently, however, the +megascleres or skeleton-spicules are not the only spicules present, for +we find smaller spicules (microscleres) of one or more kinds lying loose +in the substance of the sponge and in the external membrane, or, in the +Spongillidae only, forming a special armature for the reproductive bodies +known as gemmules. + +All sponges obtain their food in the same way, namely by means of the +currents of water set up by the flagella of the collar-cells. These +flagella, although apparently there is little concerted action among +them, cause by their rapid movements changes of pressure in the water +contained in the cavities of the sponge. The water from outside +therefore flows in at the pores and finally makes its way out of the +oscula. With the water minute particles of organic matter are brought +into the sponge, the collar-cells of which, and probably other cells, +have the power of selecting and engulfing suitable particles. Inside the +cells these particles undergo certain chemical changes, and are at least +partially digested. The resulting substances are then handed on directly +to other cells, or, as some assert, are discharged into the common +jelly, whence they are taken up by other cells. + +Sponges reproduce their kind in more ways than one, _viz._, by means of +eggs (which are fertilized as in other animals by spermatozoa), by means +of buds, and by means of the peculiar bodies called gemmules the +structure and origin of which is discussed below (p. 42). They are of +great importance in the classification of the Spongillidae. Sponges can +also be propagated artificially by means of fission, and it is probable +that this method of reproduction occurs accidentally, if not normally, +in natural circumstances. + + +GENERAL STRUCTURE OF THE SPONGILLIDAE. + +It would be impracticable in this introduction to give a full account of +the structure of the Spongillidae, which in some respects is still +imperfectly known. Students who desire further information should +consult Professor Minchin's account of the sponges in Lankester's +'Treatise on Zoology,' part ii, or, if a less technical description is +desired, Miss Sollas's contribution to the 'Cambridge Natural History,' +vol. i, in which special attention is paid to _Spongilla_. + +The diagram reproduced in fig. 1 gives a schematic view of a vertical +section through a living freshwater sponge. Although it represents the +structure of the organism as being very much simpler than is actually +the case, and entirely omits the skeleton, it will be found useful as +indicating the main features of the anatomy. + +[Illustration: Fig. 1.--Diagram of a vertical section through a +freshwater sponge (_modified from Kuekenthal_). + +A=pores; B=subdermal cavity; C=inhalent canal; D=ciliated chamber; +E=exhalent canal; F=osculum; G=dermal membrane; H=eggs; J=gemmule.] + +It will be noted that the diagram represents an individual with a single +osculum or exhalent aperture. As a rule adult Demospongiae have several +or many oscula, but even in the Spongillidae sponges occur in which there +is only one. New oscula are formed by a kind of proliferation that +renders the structure still more complex than it is when only one +exhalent aperture is present. + +The little arrows in the figure indicate the direction of the currents +of water that pass through the sponge. It enters through small holes in +the derma into a subdermal cavity, which separates the membrane from the +bulk of the sponge. This space differs greatly in extent in different +species. From the subdermal space the water is forced by the action of +the flagella into narrow tubular canals that carry it into the ciliated +chambers. Thence it passes into other canals, which communicate with +what remains of the central cavity, and so out of the oscula. + +The ciliated chambers are very minute, and the collar-cells excessively +so. It is very difficult to examine them owing to their small size and +delicate structure. Fig. 2 D represents a collar-cell of a sponge seen +under a very high power of the microscope in ideal conditions. + +[Illustration: Fig. 2.--Sponge cells. + +A=bubble-cells of _Ephydatia muelleri_, x 350 (_after Weltner_). +B=gemmule-cell of _Spongilla lacustris_ containing green corpuscles +(shaded dark), x 800 (_after Weltner_). C=gemmule-cell of _Ephydatia +blembingia_ showing "tabloids" of food-material, x 1150 (_after Evans_). +D=collar-cell of _Esperella aegagrophila_, x 1600 (_after Vosmaer and +Pekelharing_). E=three stages in the development of a gemmule-spicule of +_E. blembingia_ (_after Evans_), x 665. F=outline of porocytes of _S. +proliferens_, x ca. 1290: _e_=dermal cell; _n_=nucleus; _p_=pore; +_p.c._=pore-cell.] + +The nature of the inhalent apertures in the external membrane has been +much discussed as regards the Demospongiae, but the truth seems to be +that their structure differs considerably even in closely allied +species. At any rate this is the case as regards the Indian _Spongillae_. +In all species the membrane is composed of flattened cells of irregular +shape fitted together like the pieces of a puzzle-picture. In some +species (e. g., _Spongilla carteri_) the apertures in the membrane +consist merely of spaces between adjacent cells, which may be a little +more crowded together than is usual. But in others (e. g., _Spongilla +proliferens_ and _Spongilla crassissima_) in which the pores are +extremely small, each pore normally pierces the middle of a flat, +ring-shaped cell or porocyte. Occasionally, however, a pore may be found +that is enclosed by two narrow, crescent-shaped cells joined together at +their tips to form a ring. The porocytes of sponges like _Spongilla +carteri_ are probably not actually missing, but instead of being in the +external membrane are situated below the derma at the external entrance +to the canals that carry water to the flagellated chambers or even at +the entrance to the chambers themselves[L]. Some authors object on +theoretical grounds to the statement that porocytes exist in the +Demospongia, and it is possible that these cells have in this grade +neither the same origin as, nor a precisely similar function to, the +porocytes of other sponges. When they occur in the dermal membrane no +great difficulty is experienced in seeing them under a sufficiently high +power of the microscope, if the material is well preserved and mounted +and stained in a suitable manner[M]. In most sponges the porocytes can +contract in such a way that the aperture in their centre is practically +closed, but this power appears to be possessed by the porocytes of +_Spongilla_ only to a very limited extent, although they closely +resemble the porocytes of other sponges in appearance. + + [Footnote L: _Cf._ Weltner, "Spongillidenstudien, V," Arch. + Naturg. Berlin, lxxiii (i), p. 273 (1907).] + + [Footnote M: It is difficult to see any trace of them in + thin microtome sections. A fragment of the membrane must be + mounted whole.] + +The external membrane in many Spongillidae is prolonged round and above +the oscula so as to form an oscular collar. This structure is highly +contractile, but cannot close together. As a rule it is much more +conspicuous in living sponges than in preserved specimens. + +It is not necessary to deal here with most of the cells that +occur in the parenchyma or gelatinous part of the sponge. A full +list of the kinds that are found is given by Dr. Weltner in his +"Spongillidenstudien, V," p. 276 (Arch. Naturg. Berlin, lxxiii (i), +1907). One kind must, however, be briefly noticed as being of some +systematic importance, namely the "bubble-cells" (fig. 2 A) that are +characteristic of some species of _Ephydatia_ and other genera. These +cells are comparatively large, spherical in form; each of them contains +a globule of liquid which not only occupies the greater part of the +cell, but forces the protoplasm to assume the form of a delicate film +lining the cell-wall and covering the globule. In optical section +"bubble-cells" have a certain resemblance to porocytes, but the cell is +of course imperforate and not flattened. + + +SKELETON AND SPICULES. + +[Illustration: Fig. 3.--Radial sections of fragments of the skeletons of +_Spongillae_. + +A, _S. crassissima_ var. _crassior_ (from Rajshahi); B, _S. carteri_ +(from Calcutta); _a_=transverse, _b_=radiating fibres; _e_=external +surface of the sponge.] + +In the Spongillidae the spicules and the skeleton are more important as +regards the recognition of genera and species than the soft parts. The +skeleton is usually reticulate, but sometimes consists of a mass of +spicules almost without arrangement. The amount of spongin present is +also different in different species. The spicules in a reticulate +skeleton are arranged so as to form fibres of two kinds--radiating +fibres, which radiate outwards from the centre of the sponge and +frequently penetrate the external membrane, and transverse fibres, which +run across from one radiating fibre to another. The fibres are composed +of relatively large spicules (megascleres) arranged parallel to one +another, overlapping at the ends, and bound together by means of a more +or less profuse secretion of spongin. In some species they are actually +enclosed in a sheath of this substance. The radiating fibres are usually +more distinct and stouter than the transverse ones, which are often +represented by single spicules but are sometimes splayed out at the ends +so as to assume in outline the form of an hour-glass (fig. 3 B). The +radiating fibres frequently raise up the membrane at their free +extremities just as a tent-pole does a tent. + +Normal spicules of the skeleton are always rod-like or needle-like, and +either blunt or pointed at both ends; they are either smooth, granular, +or covered with small spines. Sometimes spicules of the same type form a +more or less irregular transverse network at the base or on the surface +of the sponge. + +[Illustration: Fig. 4.--Part of an oscular collar of _Spongilla +lacustris_ subsp. _reticulata_, showing arrangement of microscleres in +the derma (magnified).] + +From the systematist's point of view, the structure of the free spicules +found scattered in the substance and membrane of the sponge, and +especially of those that form the armature of the gemmules, is of more +importance than that of the skeleton-spicules. Free spicules are absent +in many species; when present they are usually needle-like and pointed +at the tips. In a few species, however, they are of variable or +irregular form, or consist of several or many shafts meeting in a common +central nodule. In one genus (_Corvospongilla_) they resemble a double +grappling-iron in form, having a circle of strongly recurved hooks at +both ends. The free microscleres, or flesh-spicules as they are often +called, are either smooth, granular, or spiny. + +Gemmule-spicules, which form a characteristic feature of the +Spongillidae, are very seldom absent when the gemmules are mature. They +are of the greatest importance in distinguishing the genera. In their +simplest form they closely resemble the free microscleres, but in +several genera they bear, either at or near one end or at or near both +ends, transverse disks which are either smooth or indented round the +edge. In one genus (_Pectispongilla_) they are provided at both ends not +with disks but with vertically parallel rows of spines resembling combs +in appearance. + +The simpler spicules of the Spongillidae are formed in single cells (see +fig. 2 E), but those of more complicated shape are produced by several +cells acting in concert. Each spicule, although it is formed mainly of +hydrated silica (opal), contains a slender organic filament running +along its main axis inside the silica. This filament, or rather the tube +in which it is contained, is often quite conspicuous, and in some +species (e. g., _Spongilla crassissima_) its termination is marked at +both ends of the megasclere by a minute conical protuberance in the +silica. + +Unless sponges are alchemists and can transmute one element into +another, the material of which the spicules are made must ultimately +come from the water in which the sponges live, or the rocks or other +bodies to or near which they are attached. The amount of water that must +pass through a large specimen of such a sponge as _Spongilla carteri_ in +order that it may obtain materials for its skeleton must be enormous, +for silica is an insoluble substance. I have noticed, however, that this +sponge is particularly abundant and grows with special luxuriance in +ponds in which clothes are washed with soap, and my friend Mr. G. H. +Tipper has suggested to me that possibly the alkali contained in the +soap-suds may assist the sponge in dissolving out the silica contained +in the mud at the bottom of the ponds. The question of how the mineral +matter of the skeleton is obtained is, however, one about which we know +nothing definite. + +The spongin that binds the skeleton-spicules together takes the form of +a colourless or yellowish transparent membrane, which is often +practically invisible. When very abundant it sometimes extends across +the nodes of the skeleton as a delicate veil. In some sponges it also +forms a basal membrane in contact with the object to which the sponge is +attached, and in some such cases the spongin of the radiating fibres is +in direct continuity with that of the basal membrane. + + +COLOUR AND ODOUR. + +Most freshwater sponges have a bad odour, which is more marked in some +species than in others. This odour is not peculiar to the Spongillidae, +for it is practically identical with that given out by the common marine +sponge _Halichondria panicea_. Its function is probably protective, but +how it is produced we do not know. + +The coloration of freshwater sponges is usually dull and uniform, but +_Pectispongilla aurea_ is of the brilliant yellow indicated by its name, +while many species are of the bright green shade characteristic of +chlorophyll, the colouring matter of the leaves of plants. Many species +are brown or grey, and some are almost white. + +These colours are due to one of three causes, or to a combination of +more than one of them, viz.:--(1) the inhalation of solid inorganic +particles, which are engulfed by the cells; (2) the presence in the +cells of coloured substances, solid or liquid, produced by the vital +activities of the sponge; and (3) the presence in the cells of peculiar +organized living bodies known as "green corpuscles." + +Sponges living in muddy water are often nearly black. This is because +the cells of their parenchyma are gorged with very minute solid +particles of silt. If a sponge of the kind is kept in clean water for a +few days, it often becomes almost white. An interesting experiment is +easily performed to illustrate the absorption and final elimination of +solid colouring matter by placing a living sponge (small specimens of +_Spongilla carteri_ are suitable) in a glass of clean water, and +sprinkling finely powdered carmine in the water. In a few hours the +sponge will be of a bright pink colour, but if only a little carmine is +used at first and no more added, it will regain its normal greyish hue +in a few days. + +The colouring matter produced by the sponge itself is of two +kinds--pigment, which is probably a waste product, and the substances +produced directly by the ingestion of food or in the process of its +digestion. When pigment is produced it takes the form of minute granules +lying in the cells of the parenchyma, the dermal membrane being as a +rule colourless. Very little is known about the pigments of freshwater +sponges, and even less about the direct products of metabolism. It is +apparently the latter, however, that give many otherwise colourless +sponges a slight pinkish or yellowish tinge directly due to the presence +in cells of the parenchyma of minute liquid globules. In one form of +_Spongilla carteri_ these globules turn of a dark brown colour if +treated with alcohol. The brilliant colour of _Pectispongilla aurea_ is +due not to solid granules but to a liquid or semi-liquid substance +contained in the cells. + +The green corpuscles of the Spongillidae are not present in all species. +There is every reason to think that they represent a stage in the +life-history of an alga, and that they enter the sponge in an active +condition (see p. 49). + +A fourth cause for the coloration of freshwater sponges may be noted +briefly. It is not a normal one, but occurs commonly in certain forms +(e. g., _Spongilla alba_ var. _bengalensis_). This cause is the growth +in the canals and substance of the sponge of parasitic algaae, which turn +the whole organism of a dull green colour. They do not do so, however, +until they have reduced it to a dying state. The commonest parasite of +the kind is a filamentous species particularly common in brackish water +in the Ganges delta. + + +EXTERNAL FORM AND CONSISTENCY. + +[Illustration: Fig. 5.--Part of a type-specimen of _Spongilla lacustris_ +subsp. _reticulata_ (nat. size).] + +The external form of sponges is very variable, but each species, +subspecies, or variety of the Spongillidae has normally a characteristic +appearance. The European race of _Spongilla lacustris_, for example, +consists in favourable circumstances of a flattened basal part from +which long cylindrical branches grow out; while in the Indian race of +the species these branches are flattened instead of being cylindrical, +and anastomose freely. The structure of the branches is identical with +that of the basal part. Many other species (for instance, _Spongilla +bombayensis_ and _S. ultima_) never produce branches but always consist +of lichenoid or cushion-shaped masses. The appearance of _Spongilla +crateriformis_, when it is growing on a flattened surface which allows +it to develop its natural form, is very characteristic, for it consists +of little flattened masses that seem to be running out towards one +another, just as though the sponge had been dropped, spoonful by +spoonful, in a viscous condition from a teaspoon. Some species, such as +_Trochospongilla phillottiana_, cover large areas with a thin film of +uniform thickness, while others (e. g., _Spongilla alba_ and _Ephydatia +meyeni_) consist of irregular masses, the surface of which bears +numerous irregular ridges or conical, subquadrate, or digitate +processes. In a few forms (e. g., _Corvospongilla burmanica_) the +surface is covered with small turret-like projections of considerable +regularity, and some (e. g., _Spongilla crassissima_) naturally assume a +spherical or oval shape with an absolutely smooth surface. + +The production of long branches is apparently rare in tropical +freshwater sponges. + +The form of the oscula is characteristic in many cases. No other Indian +species has them so large, or with such well-defined margins as +_Spongilla carteri_ (Pl. II, fig. 1). In many species (Pl. II, fig. 3) +they have a stellate appearance owing to the fact that grooves in the +substance of the sponge radiate round them beneath the external +membrane. In other species they are quite inconspicuous and very small. + +[Illustration: Fig. 6.--Radial section through part of a dried sponge of +_Spongilla crassissima_ (from Calcutta), x 5.] + +Spongillidae differ greatly in consistency. _Spongilla crassissima_ and +_Corvospongilla lapidosa_ are almost stony, although the former is +extremely light, more like pumice than true stone. Other species (e. g., +_Trochospongilla latouchiana_) are hard but brittle, while others again +are soft and easily compressed, as _Spongilla lacustris_, the variety +_mollis_ of _S. carteri_, and _S. crateriformis_. The consistency of a +sponge depends on two factors--the number of spicules present, and the +amount of spongin. In _Corvospongilla lapidosa_ the number of spicules +is very large indeed. They are not arranged so as to form a reticulate +skeleton but interlock in all directions, and there is hardly any +spongin associated with them. In _Spongilla crassissima_, on the other +hand, the number of spicules although large is not unusually so; but +they form a very definitely reticulate skeleton, and are bound together +by an unusually profuse secretion of spongin. In _S. carteri_ var. +_mollis_ both spicules and spongin are reduced to a minimum, and the +parenchyma is relatively more bulky than usual. + + +VARIATION. + +Sponges are very variable organisms, and even a slight change in the +environment of the freshwater species often produces a considerable +change in form and structure. Some species vary in accordance with the +season, and others without apparent cause. Not only have many given rise +to subspecies and "varieties" that possess a certain stability, but most +if not all are liable to smaller changes that apparently affect both the +individual and the breed, at any rate for a period. + +(a) _Seasonal Variation._ + +Weltner has shown in a recent paper (Arch. Natg. Berlin, lxxiii (i), p. +276, 1907) that in Europe those individuals of _Ephydatia_ which are +found (exceptionally) in an active condition in winter differ +considerably both as regards the number of their cells and their anatomy +from those found in summer. In Calcutta the majority of the individuals +of _Spongilla carteri_ that are found in summer have their external +surface unusually smooth and rounded, and contain in their parenchyma +numerous cells the protoplasm of which is gorged with liquid. These +cells give the whole sponge a faint pinkish tinge during life; but if it +is plunged in spirit, both the liquid in the cells and the spirit turn +rapidly of a dark brown colour. Specimens of _Spongilla crateriformis_ +taken in a certain tank in Calcutta during the cold weather had the +majority of the skeleton-spicules blunt, while the extremities of the +gemmule-spicules were distinctly differentiated. Specimens of the same +species taken from the same tank in July had the skeleton-spicules +pointed, while the extremities of the gemmule-spicules were much less +clearly differentiated. I have been unable to confirm this by +observations made on sponges from other tanks, but it would certainly +suggest that at any rate the breed of sponges in the tank first +investigated was liable to seasonal variation. + +(b) _Variation due directly to Environment._ + +The characteristic external form of freshwater sponges is liable in most +cases to be altered as a direct result of changes in the environment. +The following are two characteristic instances of this phenomenon. + +Certain shrubs with slender stems grow in the water at the edge of +Igatpuri Lake. The stems of these shrubs support many large examples of +_Spongilla carteri_, which are kept in almost constant motion owing to +the action of the wind on those parts of the shrubs that are not under +water. The surface of the sponges is so affected by the currents of +water thus set up against it that it is covered with deep grooves and +high irregular ridges like cockscombs. Less than a hundred yards from +the lake there is a small pond in which _Spongilla carteri_ is also +abundant. Here it grows on stones at the bottom and has the +characteristic and almost smooth form of the species. + +My second instance also refers in part to Igatpuri Lake. _Corvospongilla +lapidosa_ is common in the lake on the lower surface of stones, and also +occurs at Nasik, about thirty miles away, on the walls of a conduit of +dirty water. In the latter situation it has the form of large sheets of +a blackish colour, with the surface corrugated and the oscula +inconspicuous, while in the clear waters of the lake it is of a pale +yellowish colour, occurs in small lichenoid patches, and has its oscula +rendered conspicuous, in spite of their minute size, by being raised on +little conical eminences in such a way that they resemble the craters of +volcanoes in miniature. + +Both the European and the Indian races of _Spongilla lacustris_ fail to +develop branches if growing in unfavourable conditions. In specimens +obtained from the River Spree near Berlin these structures are sometimes +many inches in length; while in mature specimens taken under stones in +Loch Baa in the Island of Mull the whole organism consisted of a minute +cushion-shaped mass less than an inch in diameter, and was also +deficient in spicules. Both these breeds belong to the same species, and +probably differ as a direct result of differences in environment. + +(c) _Variation without apparent cause._ + +Plate I in this volume illustrates an excellent example of variation in +external form to which it is impossible to assign a cause with any +degree of confidence. The three specimens figured were all taken in the +same pond, and at the same season, but in different years. It is +possible that the change in form, which was not peculiar to a few +individuals but to all those in several adjacent ponds, was due to a +difference in the salinity of the water brought about by a more or less +abundant rainfall; but of this I have been able to obtain no evidence in +succeeding years. + +Many Spongillidae vary without apparent cause as regards the shape, size, +and proportions of their spicules. This is the case as regards most +species of _Euspongilla_ and _Ephydatia_, and is a fact to which careful +consideration has to be given in separating the species. + + +NUTRITION. + +Very little is known about the natural food of freshwater sponges, +except that it must be of an organic nature and must be either in a very +finely divided or in a liquid condition. The cells of the sponge seem to +have the power of selecting suitable food from the water that flows past +them, and it is known that they will absorb milk. The fact that they +engulf minute particles of silt does not prove that they lack the power +of selection, for extraneous matter is taken up by them not only as food +but in order that it may be eliminated. Silt would soon block up the +canals and so put a stop to the vital activity of the sponge, if it were +not got rid of, and presumably it is only taken into the cells in order +that they may pass it on and finally disgorge it in such a way or in +such a position that it may be carried out of the oscula. The siliceous +part of it may be used in forming spicules. + +It is generally believed that the green corpuscles play an important +part in the nutrition of those sponges in which they occur, and there +can be no doubt that these bodies have the power peculiar to all +organisms that produce chlorophyll of obtaining nutritive substances +direct from water and carbonic oxide through the action of sunlight. +Possibly they hand on some of the nourishment thus obtained to the +sponges in which they live, or benefit them by the free oxygen given out +in the process, but many Spongillidae do well without them, even when +living in identical conditions with species in which they abound. + + +REPRODUCTION. + +Both eggs and buds are produced by freshwater sponges (the latter rarely +except by one species), while their gemmules attain an elaboration of +structure not observed in any other family of sponges. + +Probably all Spongillidae are potentially monoecious, that is to say, +able to produce both eggs and spermatozoa. In one Indian species, +however, in which budding is unusually common (viz. _Spongilla +proliferens_), sexual reproduction takes place very seldom, if ever. It +is not known whether the eggs of sponges are fertilized by spermatozoa +from the individual that produces the egg or by those of other +individuals, but not improbably both methods of fertilization occur. + +The egg of a freshwater sponge does not differ materially from that of +other animals. When mature it is a relatively large spherical cell +containing abundant food-material and situated in some natural cavity of +the sponge. In the earlier stages of its growth, however, it exhibits +amoeboid movements, and makes its way through the common jelly. As it +approaches maturity it is surrounded by other cells which contain +granules of food-material. The food-material is apparently transferred +by them in a slightly altered form to the egg. The egg has no shell, but +in some species (e. g. _Ephydatia blembingia_[N]) it is surrounded, +after fertilization, by gland-cells belonging to the parent sponge, +which secrete round it a membrane of spongin. Development goes on within +the chamber thus formed until the larva is ready to assume a free life. + + [Footnote N: Rec. Ind. Mus. i, p. 269 (1907).] + +The spermatozoon is also like that of other animals, consisting of a +rounded head and a lash-like tail, the movements of which enable it to +move rapidly through the water. Spermatozoa are produced in _Spongilla_ +from spherical cells not unlike the eggs in general appearance. The +contents of these cells divide and subdivide in such a way that they +finally consist of a mass of spermatozoa surrounded by a single covering +cell, which they finally rupture, and so escape. + +[Illustration: Fig. 7.--Diagram of a vertical section through the +gemmule of _Spongilla proliferens_. + +A=cellular contents; B=internal chitinous layer; C=external chitinous +layer; D=pneumatic coat; E=gemmule-spicule; F=external membrane; +G=foraminal tubule.] + +Gemmules are asexual reproductive bodies peculiar to the sponges, but +not to the Spongillidae. They resemble the statoblasts of the +phylactolaematous polyzoa in general structure as well as in function, +which is mainly that of preserving the race from destruction by such +agencies as drought, starvation, and temperatures that are either too +high or too low for its activities. This function they are enabled to +perform by the facts that they are provided with coverings not only very +hard but also fitted to resist the unfavourable agencies to which the +gemmules are likely to be exposed, and that they contain abundant +food-material of which use can be made as soon as favourable conditions +occur again. + +Internally the gemmule consists of a mass of cells containing +food-material in what may be called a tabloid form, for it consists of +minutely granular plate-like bodies. These cells are enclosed in a +flask-like receptacle, the walls of which consist of two chitinous +layers, a delicate inner membrane and an outer one of considerable +stoutness. The mouth of the flask is closed by an extension of the inner +membrane, and in some species is surrounded by a tubular extension of +the external membrane known as the foraminal tubule. Externally the +gemmule is usually covered by what is called a "pneumatic coat," also of +"chitin" (spongin), but usually of great relative thickness and +honeycombed by spaces which contain air, rendering the structure +buoyant. The pneumatic coat also contains the microscleres +characteristic of the species; it is often limited externally by a third +chitinous membrane, on which more gemmule-spicules sometimes lie +parallel to the surface. + +The cells from which those of the gemmules are derived are akin in +origin to those that give rise to eggs and spermatozoa. Some zoologists +are therefore of the opinion that the development of the gemmule is an +instance of parthenogenesis--that is to say of an organism arising from +an egg that has not been fertilized. But some of the collar-cells, +although most of them originate from the external ciliated cells of the +larva, have a similar origin. The building-up of the gemmule affords an +excellent instance of the active co-operation that exists between the +cells of sponges, and of their mobility, for the food-material that has +to be stored up is brought by cells from all parts of the sponge, and +these cells retire after discharging their load into those of the young +gemmule. + +The formation of the gemmule of _Ephydatia blembingia_, a Malayan +species not yet found in India, is described in detail by Dr. R. Evans +(Q. J. Microsc. Sci. London, xliv, p. 81, 1901). + +Gemmules are produced by the freshwater sponges of Europe, N. America +and Japan at the approach of winter, but in the tropical parts of India +they are formed more frequently at the approach of the hot weather (p. +4). After they are fully formed the sponge that has produced them dies, +and as a rule disintegrates more or less completely. In some species, +however, the greater part of the skeleton remains intact, if it is not +disturbed, and retains some of the gemmules in its meshwork, where they +finally germinate. Other gemmules are set free. Some of them float on +the surface of the water; others sink to the bottom. In any case all of +them undergo a period of quiescence before germinating. It has been +found that they can be kept dry for two years without dying. + +The function of the special spicules with which the gemmules of the +Spongillidae are provided appears to be not only to protect them but more +especially to weight them to the extent suitable to the habits of each +species. Species that inhabit running water, for example, in some cases +have heavier gemmule-spicules than those that live in stagnant water, +and their gemmules are the less easily carried away by the currents of +the river. The gemmules of sponges growing in lakes are sometimes +deficient in spicules. This is the case as regards the form of +_Spongilla lacustris_ found in Lake Baa, Isle of Mull, as regards _S. +helvetica_ from the Lake of Geneva, _S. moorei_ from Lake Tanganyika, +and _S. coggini_ from Tali-Fu in Yunnan; also as regards the species of +_Spongilla_ and _Ephydatia_ found in Lake Baikal, many of the sponges of +which are said never to produce gemmules. + +Except in the genus _Corvospongilla_ and the subgenus _Stratospongilla_, +in both of which the air-spaces of the gemmules are usually no more than +cavities between different chitinous membranes, the pneumatic coat is +either "granular" or "cellular." Neither of these terms, however, must +be understood in a physiological sense, for what appear to be granules +in a granular coat are actually minute bubbles of air contained in +little cavities in a foam-like mass of chitin (or rather spongin), while +the cells in a cellular one are only larger and more regular air-spaces +with thin polygonal walls and flat horizontal partitions. The walls of +these spaces are said in some cases to contain a considerable amount of +silica. + +The gemmules with their various coverings are usually spherical in +shape, but in some species they are oval or depressed in outline. They +lie as a rule free in the substance of the sponge, but in some species +adhere at its base to the object to which it is attached. In some +species they are joined together in groups, but in most they are quite +free one from another. + +Reproductive buds[O] are produced, so far as is known, by very few +Spongillidae, although they are common enough in some other groups of +sponges. In the only freshwater species in which they have been found to +form a habitual means of reproduction, namely in _Spongilla +proliferens_, they have much the appearance of abortive branches, and it +is possible that they have been overlooked for this reason in other +species, for they were noticed by Laurent in _Spongilla lacustris_ as +long ago as 1840 (CR. Se. Acad. Sci. Paris, xi, p. 478). The buds +noticed by Laurent, however, were only produced by very young sponges, +and were of a different nature from those of _S. proliferens_, perhaps +representing a form of fission rather than true budding (see 'Voyage de +la Bonite: Zoophytologie,' Spongiaires, pl. i (Paris, 1844)). + + [Footnote O: Proliferation whereby more than one osculum is + produced is really a form of budding, but in most sponges + this has become no longer a mode of reproduction but the + normal method by which size is increased, and must therefore + be considered merely as a vegetative process.] + +In _Spongilla proliferens_, a common Indian species, the buds arise as +thickenings of the strands of cells accompanying the radiating +spicule-fibres of the skeleton, which project outwards from the surface +of the sponge. The thickenings originate beneath the surface and +contain, at the earliest stage at which I have as yet examined them, all +the elements of the adult organism (_i. e._ flesh-spicules, ciliated +chambers, efferent and afferent canals, parenchyma-cells of various +sorts) except skeleton fibres, gemmules, and a dermal membrane. A +section at this period closely resembles one of an adult sponge, except +that the structure is more compact, the parenchyma being relatively +bulky and the canals of small diameter. + +Laurent observed reproduction by splitting in young individuals of +_Spongilla_, but I have not been able to obtain evidence myself that +this method of reproduction occurs normally in Indian species. In +injured specimens of _Spongilla carteri_, however, I have observed a +phenomenon that seems to be rather an abnormal form of budding, little +rounded masses of cells making their way to the ends of the radiating +skeleton fibres and becoming transformed into young sponges, which break +loose and so start an independent existence. Possibly the buds observed +by Laurent in _S. lacustris_ were of a similar nature. + + +DEVELOPMENT. + + +(a) _From the Egg._ + +After fertilization, the egg, lying in its cavity in the sponge, +undergoes a complete segmentation; that is to say, becomes divided into +a number of cells without any residuum remaining. The segmentation, +however, is not equal, for it results in the formation of cells of two +distinct types, one larger and less numerous than the other. As the +process continues a pear-shaped body is produced, solid at the broader +end, which consists of the larger cells, but hollow at the other. +Further changes result in the whole of the external surface becoming +ciliated or covered with fine protoplasmic lashes, each of which arises +from a single small cell; considerable differentiation now takes place +among the cells, and spicules begin to appear. At this stage or earlier +(for there seem to be differences in different species and individuals +as to the stage at which the young sponge escapes) the larva makes its +way out of the parent sponge. After a brief period of free life, in +which it swims rapidly through the water by means of its cilia, it fixes +itself by the broad end to some solid object (from which it can never +move again) and undergoes a final metamorphosis. During this process the +ciliated cells of the external layer make their way, either by a +folding-in of the whole layer or in groups of cells, into the interior, +there change into collar-cells and arrange themselves in special +cavities--the ciliated chambers of the adult. Finally an osculum, pores, +&c., are formed, and the sponge is complete. + +This, of course, is the merest outline of what occurs; other changes +that take place during the metamorphosis are of great theoretical +interest, but cannot be discussed here. The student may refer to Dr. R. +Evans's account of the larval development of _Spongilla lacustris_ in +the Q. J. Microsc. Sci. London, xlii, p. 363 (1899). + +(b) _From the Gemmule._ + +The period for which the gemmule lies dormant probably depends to some +extent upon environment and to some extent on the species to which it +belongs. Carter found that if he cleaned gemmules with a handkerchief +and placed them in water exposed to sunlight, they germinated in a few +days; but in Calcutta gemmules of _Spongilla alba_ var. _bengalensis_ +treated in this way and placed in my aquarium at the beginning of the +hot weather, did not germinate until well on in the "rains." Even then, +after about five months, only a few of them did so. Zykoff found that in +Europe gemmules kept for two years were still alive and able to +germinate. + +Germination consists in the cellular contents of the gemmule bursting +the membrane or membranes in which they are enclosed, and making their +way out of the gemmule in the form of a delicate whitish mass, which +sometimes issues through the natural aperture in the outer chitinous +coat and sometimes through an actual rent in this coat. In the latter +case the development of the young sponge is more advanced than in the +former. + +The fullest account of development from the gemmule as yet published is +by Zykoff, and refers to _Ephydatia_ in Europe (Biol. Centralbl. Berlin, +xii, p. 713, 1892). + +His investigations show that the bursting of the gemmule is not merely a +mechanical effect of moisture or any such agency but is due to +development of the cellular contents, which at the time they escape have +at least undergone differentiation into two layers. Of the more +important soft structures in the sponge the osculum is the first to +appear, the ciliated chambers being formed later. This is the opposite +of what occurs in the case of the bud, but in both cases the aperture +appears to be produced by the pressure of water in the organism. The +manner and order in which the different kinds of cells originate in the +sponge derived from a gemmule give support to the view that the +primitive cell-layers on which morphologists lay great stress are not of +any great importance so far as sponges are concerned. + +(c) _Development of the Bud._ + +As the bud of _Spongilla proliferens_ grows it makes its way up the +skeleton-fibre to which it was originally attached, pushing the dermal +membrane, which expands with its growth, before it. The skeleton-fibre +does not, however, continue to grow in the bud, in which a number of +finer fibres make their appearance, radiating from a point approximately +at the centre of the mass. As the bud projects more and more from the +surface of the sponge the dermal membrane contracts at its base, so as +finally to separate it from its parent. Further details are given on p. +74. + + +HABITAT. + +Mr. Edward Potts[P], writing on the freshwater sponges of North America, +says:--"These organisms have occasionally been discovered growing in +water unfit for domestic uses; but as a rule they prefer pure water, and +in my experience the finest specimens have always been found where they +are subjected to the most rapid currents." True as this is of the +Spongillidae of temperate climates, it is hardly applicable to those of +tropical India, for in this country we find many species growing most +luxuriantly and commonly in water that would certainly be considered +unfit for domestic purposes in a country in which sanitation was treated +as a science. Some species, indeed, are only found in ponds of water +polluted by human agency, and such ponds, provided that other conditions +are favourable, are perhaps the best collecting grounds. Other +favourable conditions consist in a due mixture of light and shade, a +lack of disturbance such as that caused by cleaning out the pond, and +above all in the presence of objects suitable for the support of +sponges. + + [Footnote P: P. Ac. Philad. 1887, p. 162.] + +I do not know exactly why light and shade must be mixed in a habitat +favourable for the growth of sponges, for most species prefer shade, if +it be not too dense; but it is certainly the case that, with a few +exceptions, Indian Spongillidae flourish best in water shaded at the +edges by trees and exposed to sunlight elsewhere. One of the exceptions +to this rule is the Indian race of _Spongilla lucustris_, which is found +in small pools of water in sand-dunes without a particle of shade. +Several species are only found on the lower surface of stones and roots +in circumstances which do not suggest that their position merely +protects them from mud, which, as Mr. Potts points out, is their "great +enemy." A notable instance is _Trochospongilla pennsylvanica_, which is +found hiding away from light in America and Europe as well as in India. + +It is curious that it should be easy to exterminate the sponges in a +pond by cleaning it out, for one would have thought that sufficient +gemmules would have remained at the edge, or would have been brought +rapidly from elsewhere, to restock the water. Mr. Green has, however, +noted that _Spongilla carteri_ has disappeared for some years from a +small lake at Peradeniya in which it was formerly abundant, owing to the +lake having been cleaned out, and I have made similar observations on +several occasions in Calcutta. + +The question of the objects to which sponges attach themselves is one +intimately connected with that of the injury done them by mud. The delta +of the Ganges is one of the muddiest districts on earth. There are no +stones or rocks in the rivers and ponds, but mud everywhere. If a sponge +settles in the mud its canals are rapidly choked, its vital processes +cease, and it dies. In this part of India, therefore, most sponges are +found fixed either to floating objects such as logs of wood, to vertical +objects such as the stems of bulrushes and other aquatic plants, or to +the tips of branches that overhang the water and become submerged during +the "rains." In Calcutta man has unwittingly come to the assistance of +the sponges, not only by digging tanks but also by building +"bathing-ghats" of brick at the edge, and constructing, with aesthetic +intentions if not results, masses of artificial concrete rocks in or +surrounding the water. There are at least two sponges (the typical form +of _Spongilla alba_ and _Ephydatia meyeni_) which in Calcutta are only +found attached to such objects. The form of _S. alba_, however, that is +found in ponds of brackish water in the Gangetic delta has not derived +this artificial assistance from man, except in the few places where +brick bridges have been built, and attaches itself to the stem and roots +of a kind of grass that grows at the edge of brackish water. This sponge +seems to have become immune even to mud, the particles of which are +swallowed by its cells and finally got rid of without blocking up the +canals. + +Several Indian sponges are only found adhering to stones and rocks. +Among these species _Corvospongilla lapidosa_ and our representatives of +the subgenus _Stratospongilla_ are noteworthy. Some forms (e. g. +_Spongilla carteri_ and _S. crateriformis_) seem, however, to be just as +much at home in muddy as in rocky localities, although they avoid the +mud itself. + +There is much indirect evidence that the larvae of freshwater sponges +exercise a power of selection as regards the objects to which they affix +themselves on settling down for life. + +Few Spongillidae are found in salt or brackish water, but _Spongilla +alba_ var. _bengalensis_ has been found in both, and is abundant in the +latter; indeed, it has not been found in pure fresh water. _Spongilla +travancorica_ has only been found in slightly brackish water, while _S. +lacustris_ subsp. _reticulata_ and _Dosilia plumosa_ occur in both fresh +and brackish water, although rarely in the latter. The Spongillidae are +essentially a freshwater family, and those forms that are found in any +but pure fresh water must be regarded as aberrant or unusually tolerant +in their habits, not as primitive marine forms that still linger halfway +to the sea. + + +ANIMALS AND PLANTS COMMONLY ASSOCIATED WITH +FRESHWATER SPONGES. + + +(a) _Enemies._ + +Freshwater sponges have few living enemies. Indeed, it is difficult to +say exactly what is an enemy of a creature so loosely organized as a +sponge. There can be little doubt, in any case, that the neuropteroid +larva (_Sisyra indica_) which sucks the cells of several species should +be classed in this category, and it is noteworthy that several species +of the same genus also occur in Europe and N. America which also attack +sponges. Other animals that may be enemies are a midge larva (_Tanypus_ +sp.) and certain worms that bore through the parenchyma (p. 93), but I +know of no animal that devours sponges bodily, so long as they are +uninjured. If their external membrane is destroyed, they are immediately +attacked by various little fish and also by snails of the genera +_Limnaea_ and _Planorbis_, and prawns of the genus _Palaemon_. + +Their most active and obvious enemy is a plant, not an animal,--to wit, +a filamentous alga that blocks up their canals by its rapid growth (p. +79). + +(b) _Beneficial Organisms._ + +The most abundant and possibly the most important organisms that may be +considered as benefactors to the Spongillidae are the green corpuscles +that live in the cells of certain species (fig. 2, p. 31), notably +_Spongilla lacustris_, _S. proliferens_, and _Dosilia plumosa_. I have +already said that these bodies are in all probability algae which live +free in the water and move actively at one stage of their existence, but +some of them are handed on directly from a sponge to its descendants in +the cells of the gemmule. In their quiescent stage they have been +studied by several zoologists, notably by Sir Ray Lankester[Q] and Dr. +W. Weltner[R], but the strongest light that has been cast on their +origin is given by the researches of Dr. F. W. Gamble and Mr. F. Keeble +(Q. J. Microsc. Sci. London, xlvii, p. 363, 1904, and li, p. 167, 1907). +These researches do not refer directly to the Spongillidae but to a +little flat-worm that lives in the sea, _Convoluta roscoffiensis_. The +green corpuscles of this worm so closely resemble those of _Spongilla_ +that we are justified in supposing a similarity of origin. It has been +shown by the authors cited that the green corpuscles of the worm are at +one stage minute free-living organisms provided at one end with four +flagella and at the other with a red pigment spot. The investigators are +of the opinion that these organisms exhibit the essential characters of +the algae known as Chlamydomonadae, and that after they have entered the +worm they play for it the part of an excretory system. + + [Footnote Q: Q. J. Microsc. Sci. London, xxii. p. 229 + (1882).] + + [Footnote R: Arch. Naturg. Berlin, lix (i), p. 260 (1893).] + +As they exist in the cells of _Spongilla_ the corpuscles are minute oval +bodies of a bright green colour and each containing a highly refractile +colourless granule. A considerable number may be present in a single +cell. It is found in European sponges that they lose their green colour +if the sponge is not exposed to bright sunlight. In India, however, +where the light is stronger, this is not always the case. Even when the +colour goes, the corpuscles can still be distinguished as pale images of +their green embodiment. They are called _Chlorella_ by botanists, who +have studied their life-history but have not yet discovered the full +cycle. See Beyerinck in the Botan. Zeitung for 1890 (vol. xlviii, p. +730, pl. vii; Leipzig), and for further references West's 'British +Freshwater Algae,' p. 230 (1904). + +The list of beneficent organisms less commonly present than the green +corpuscles includes a _Chironomus_ larva that builds parchment-like +tubes in the substance of _Spongilla carteri_ and so assists in +supporting the sponge, and of a peculiar little worm (_Chaetogaster +spongillae_[S]) that appears to assist in cleaning up the skeleton of the +same sponge at the approach of the hot weather and in setting free the +gemmules (p. 93). + + [Footnote S: Journ. As. Soc. Beng. n. s. ii, 1906, p. 189.] + +(c) _Organisms that take shelter in the Sponge or adhere to it +externally._ + +There are many animals which take shelter in the cavities of the sponge +without apparently assisting it in any way. Among these are the little +fish _Gobius alcockii_, which lays its eggs inside the oscula of _S. +carteri_, thus ensuring not only protection but also a proper supply of +oxygen for them (p. 94); the molluscs (_Corbula_, spp.) found inside _S. +alba_ var. _bengalensis_ (p. 78); and the Isopod (_Tachaea +spongillicola_) that makes its way into the oscula of _Spongilla +carteri_ and _S. crateriformis_ (pp. 86, 94). + +In Europe a peculiar ciliated Protozoon (_Trichodina spongillae_) is +found attached to the external surface of freshwater sponges. I have +noticed a similar species at Igatpuri on _Spongilla crateriformis_, but +it has not yet been identified. It probably has no effect, good or bad, +on the sponge. + + +FRESHWATER SPONGES IN RELATION TO MAN. + +In dealing with _Spongilla carteri_ I have suggested that sponges may be +of some hygienic importance in absorbing putrid organic matter from +water used both for ablutionary and for drinking purposes, as is so +commonly the case with regard to ponds in India. Their bad odour has +caused some species of Spongillidae to be regarded as capable of +polluting water, but a mere bad odour does not necessarily imply that +they are insanitary. + +Unless my suggestion that sponges purify water used for drinking +purposes by absorbing putrid matter should prove to be supported by +fact, the Spongillidae cannot be said to be of any practical benefit to +man. The only harm that has been imputed to them is that of polluting +water[T], of blocking up water-pipes by their growth--a very rare +occurrence,--and of causing irritation to the human skin by means of +their spicules--a still rarer one. At least one instance is, however, +reported in which men digging in a place where a pond had once been were +attacked by a troublesome rash probably due to the presence of +sponge-spicules in the earth, and students of the freshwater sponges +should be careful not to rub their eyes after handling dried specimens. + + [Footnote T: See Potts, Proc. Ac. Philad. 1884, p. 28.] + + +INDIAN SPONGILLIDAE COMPARED WITH THOSE OF OTHER COUNTRIES. + +In Weltner's catalogue of the freshwater sponges (1895) seventy-six +recent species of Spongillidae (excluding _Lubosmirskia_) are enumerated, +and the number now known is well over a hundred. In India we have +twenty-nine species, subspecies, and varieties, while from the whole of +Europe only about a dozen are known. In the neighbourhood of Calcutta +nine species, representing three genera and a subgenus, have been found; +all of them occur in the Museum tank. The only other region of similar +extent that can compare with India as regards the richness of its +freshwater sponge fauna is that of the Amazon, from which about twenty +species are known. From the whole of North America, which has probably +been better explored than any other continent so far as Spongillidae are +concerned, only twenty-seven or twenty-eight species have been recorded. + +The Indian species fall into seven genera, one of which (_Spongilla_) +consists of three subgenera. With one exception (that of +_Pectispongilla_, which has only been found in Southern India) these +genera have a wide distribution over the earth's surface, and this is +also the case as regards the subgenera of Spongilla. Four genera +(_Heteromeyenia_, _Acalle_, _Parmula_, and _Uruguaya_) that have not yet +been found in India are known to exist elsewhere. + +Five of the Indian species are known to occur in Europe, viz., +_Spongilla lacustris_, _S. crateriformis_, _S. carteri_, _S. fragilis_, +_Trochospongilla pennsylvanica_; while _Ephydatia meyeni_ is +intermediate between the two commonest representatives of its genus in +the Holarctic Zone, _Ephydatia fluviatilis_ and _E. muelleri_. Of the +species that occur both in India and in Europe, two (_Spongilla +lacustris_ and _S. fragilis_) are found in this country in forms +sufficiently distinct to be regarded as subspecies or local races. +Perhaps this course should also be taken as regards the Indian forms of +_S. carteri_, of which, however, the commonest of the Indian races would +be the typical one; but _S. crateriformis_ and _T. pennsylvanica_ seem +to preserve their specific characters free from modification, whether +they are found in Europe, Asia, or America. + +The freshwater sponges of Africa have been comparatively little studied, +but two Indian species have been discovered, _S. bombayensis_ in Natal +and _S. alba_ var. _cerebellata_ in Egypt. Several of the species from +the Malabar Zone are, moreover, closely allied to African forms (p. 11). + + +FOSSIL SPONGILLIDAE. + +The Spongillidae are an ancient family. Young described a species +(_Spongilla purbeckensis_) from the Upper Jurassic of Dorset (Geol. Mag. +London (new series) v, p. 220 (1878)), while spicules, assigned by +Ehrenberg to various genera but actually those of _Spongilla lacustris_ +or allied forms, have been found in the Miocene of Bohemia (see +Ehrenberg's 'Atlas fuer Micro-Geologie,' pl. xi (Leipzig, 1854), and +Traxler in Foeldt. Koezl., Budapest, 1895, p. 211). _Ephydatia_ is also +known in a fossil condition, but is probably less ancient than +_Spongilla_. + +Ehrenberg found many sponge spicules in earth from various parts of the +Indian Empire (including Baluchistan, Mangalore, Calcutta, the Nicobars +and Nepal) and elsewhere, and it might be possible to guess at the +identity of some of the more conspicuous species figured in his 'Atlas.' +The identification of sponges from isolated spicules is, however, always +a matter of doubt, and in some cases Ehrenberg probably assigned +spicules belonging to entirely different families or even orders to the +same genus, while he frequently attributed the different spicules of the +same species to different genera. Among his fossil (or supposed fossil) +genera that may be assigned to the Spongillidae wholly or in part are +_Aphidiscus_, _Spongolithis_, _Lithastericus_ and _Lithosphaeridium_, +many of the species of these "genera" certainly belonging to _Spongilla_ +and _Ephydatia_. + + +ORIENTAL SPONGILLIDAE NOT YET FOUND IN INDIA. + +Few freshwater sponges that have not been found in India are as yet +known from the Oriental Region, and there is positive as well as +negative evidence that Spongillidae are less abundant in Malaysia than in +this country. The following list includes the names of those that have +been found, with notes regarding each species. It is quite possible that +any one of them may be found at any time within the geographical +boundaries laid down for this 'Fauna.' I have examined types or co-types +in all cases except that of _Ephydatia fortis_, Weltner. + +I. _Spongilla_ (_Euspongilla_) _microsclerifera_*, Annandale +(Philippines). P. U.S. Mus. xxxvii, p. 131 (1909). + +This sponge is closely related to _S. lacustris_, but apparently does +not produce branches. It is remarkable for the enormous number of +microscleres in its parenchyma. + +II. _S._ (_Euspongilla_) _philippinensis_*, Annandale (Philippines). P. +U.S. Mus. xxxvi, p. 629 (1909). + +Related to _S. alba_ and still more closely to _S. sceptrioides_ of +Australia. From the former it is readily distinguished by having +minutely spined megascleres, green corpuscles, slender gemmule-spicules +with short spines and no free microscleres. + +III. _S._ (? _Euspongilla_) _yunnanensis_*, Annandale (W. China). Rec. +Ind. Mus. v, p. 197 (1910). + +Apparently allied to _S. philippinensis_ but with smooth +skeleton-spicules and a more delicate skeleton. + +IV. _S._ (_Stratospongilla_) _sinensis_*, Annandale (Foochow, China). P. +U.S. Mus. xxxviii, p. 183 (1910). + +This species and _S. clementis_ are referred to _Stratospongilla_ with +some doubt. Their gemmules are intermediate in structure between those +of that subgenus and those of _Euspongilla_. In _S. sinensis_ the +gemmules are packed together in groups at the base of the sponge, and +their spicules are smooth, stout, and gradually pointed. + +V. _S._ (_Stratospongilla_) _clementis_*, Annandale (Philippines). P. +U.S. Mus. xxxvi, p. 631 (1909). + +The gemmules are single and closely adherent at the base of the sponge. +Their spicules are very slender and minutely spined. + +VI. _S._ (? _Stratospongilla_) _coggini_*, Annandale (W. China). Rec. +Ind. Mus. v, p. 198 (1910). + +The gemmules apparently lack microscleres. They resemble those of _S. +clementis_, to which the species is probably related, in other respects. +The skeleton-spicules are spiny and rather stout, the species being +strongly developed at the two ends. + +VII. _S._ (_Stratospongilla_) _sumatrana_*, Weber (Malay Archipelago). +Zool. Ergebnisse einer Reise in Niederlaendisch Ost-Indien, i. p. 38 +(1890). + +Closely allied to _S. indica_ (p. 100) but with pointed +skeleton-spicules. + +VIII. _Ephydatia fortis_, Weltner (Philippines). Arch. Naturgesch. +lxi(i), p. 141 (1895). + +This species is remarkable for the great development of the spines on +the shaft of the gemmule-spicules. + +IX. _Ephydatia bogorensis_*, Weber (Malay Archipelago). Zool. Ergebnisse +einer Reise in Niederlaendisch Ost-Indien, i, p. 33 (1890). + +The gemmule-spicules have rather narrow flattish disks, the edge of +which is feebly but closely serrated. + +X. _E. blembingia_*, Evans (Malay Peninsula). Q. J. Microsc. Sci. +London, xliv, p. 81 (1901). + +The gemmules resemble those of _Dosilia plumosa_ but are spherical. +There are no free microscleres. + +XI. _Tubella vesparium_*, v. Martens (Borneo). Arch. Naturg. + +Berlin, xxxiv, p. 62 (1868). + +Closely related to _T. vesparioides_ (p. 189), but with spiny +megascleres. + +As regards _Spongilla decipiens_*, Weber, from the Malay Archipelago, +see p. 97. + + +II. + +HISTORY OF THE STUDY OF FRESHWATER SPONGES. + +The bath-sponge was known to the Greeks at an early date, and Homer +refers to it as being used for cleansing furniture, for expunging +writing, and for ablutionary purposes. He also mentions its peculiar +structure, "with many holes." "Many things besides," wrote the English +naturalist Ray in his 'Historia Plantarum' (1686), "regarding the powers +and uses of sponges have the Ancients: to them refer." Ray himself +describes at least one freshwater species, which had been found in an +English river, and refers to what may be another as having been brought +from America. In the eighteenth century Linne, Pallas and other authors +described the commoner European Spongillidae in general terms, sometimes +as plants and sometimes as animals, more usually as zoophytes or +"plant-animals" partaking of the nature of both kingdoms. The gemmules +were noted and referred to as seeds. The early naturalists of the +Linnaean Epoch, however, added little to the general knowledge of the +Spongillidae, being occupied with theory in which theological disputes +were involved rather than actual observation, and, notwithstanding the +fact that the animal nature of sponges was clearly demonstrated by +Ellis[U] in 1765, it was not until the nineteenth century was well +advanced that zoologists could regard sponges in anything like an +impartial manner. + + [Footnote U: Phil. Trans. Roy. Soc. lv, p. 280.] + +One of the pioneers in the scientific study of the freshwater forms was +the late Dr. H. J. Carter, who commenced his investigations, and carried +out a great part of them, in Bombay with little of the apparatus now +considered necessary, and with a microscope that must have been grossly +defective according to modern ideas. His long series of papers +(1848-1887) published in the 'Annals and Magazine of Natural History' is +an enduring monument to Indian zoology, and forms the best possible +introduction to the study of the Spongillidae. Even his earlier mistakes +are instructive, for they are due not so much to actual errors in +observation as to a faithful transcription of what was observed with +faulty apparatus. + +Contemporary with Carter were two authors whose monographs on the +freshwater sponges did much to advance the study of the group, namely, +J. S. Bowerbank, whose account of the species known at the time was +published in the 'Proceedings of the Zoological Society of London' in +1882, and the veteran American naturalist Mr. Edward Potts, whose study +of the freshwater sponges culminated in his monograph published in the +'Proceedings of the Academy of Natural Sciences of Philadelphia' in +1887. Carter's own revision of the group was published in the 'Annals +and Magazine of Natural History' in 1881. The names of Vejdovsky, who +prefaced Potts's monograph with an account of the European species, and +of Dybowsky, who published several important papers on classification, +should also be mentioned, while Weltner's catalogue of the known species +(1895) is of the greatest possible value to students of the group. + +Many authors have dealt with the physiology, reproduction and +development of the Spongillidae, especially in recent years; Dr. R. +Evans's description of the larva of _Spongilla lacustris_ (1899), and +his account of the development of the gemmule in _Ephydatia blembingia_ +(1901), Zykoff's account of the development of the gemmule and of the +sponge from the gemmule (1892), and Weltner's observations on colour and +other points (1893, 1907), may be mentioned in particular. Laurent's +observations on development (1844), which were published in the 'Voyage +de la Bonite,' and especially the exquisite plates which accompany them, +have not received the notice they deserve, probably on account of their +method of publication. + + +LITERATURE. + +The fullest account of the literature on the Spongillidae as yet +published will be found in the first of Weltner's 'Spongillidenstudien' +(Archiv fuer Naturgeschichte, lix (i), p. 209, 1893). Unfortunately it +contains no references of later date than 1892. The following list is +not a complete bibliography, but merely a list of books and papers that +should prove of use to students of the Oriental Spongillidae. + +(a) _Works of Reference._ + +1863. BOWERBANK, "A Monograph of the Spongillidae," P. Zool. Soc. London, +1863, pp. 440-472, pl. xxxviii. + +1867. GRAY, J. E., "Notes on the arrangement of Sponges, with the +description of some new genera." _ibid._ 1867, pp. 492-558. + +1881. CARTER, "History and classification of the known species of +_Spongilla_," Ann. Nat. Hist. (5) vii, pp. 77-107, pls. v, vi. + +1883. VEJDOVSKY, "Die Suesswasserschwaemme Boehmens," Abh. Koen. Boehm. Ges. +Wiss. (math.-natur. Classe), xii, pp. 1-43, pls. i-iii. + +1887. VOSMAER, "Spongien (Porifera)," in Bronn's Thier-Reichs. + +1887. POTTS, "Contributions towards a synopsis of the American forms of +Fresh-Water Sponges, with descriptions of those named by other authors +and from all parts of the world," P. Ac. Philad. pp. 158-279, pls. +v-xii. + +1887. VEJDOVSKY, "Diagnosis of the European Spongillidae," _ibid._ pp. +172-180. + +1888. WIERZEJSKI, "Beitrag zur Kenntnis der Suesswasserschwaemme," Verh. +k.-k. zool.-bot. Ges. Wien, xxxviii, pp. 529-536, pl. xii. + +1891. WELTNER, in Zacharias's Die Tier- und Pflanzenwelt des +Suesswassers: I, Die Suesswasserschwaemme. + +1895. WELTNER, "Spongillidenstudien, III," Arch. Naturg. Berlin, lxi +(i), pp. 114-144. + +1895. KORSCHELT and HEIDER, Text-book of the Embryology of +Invertebrates: English edition, prepared by E. L. Mark and W. McM. +Woodworth, Vol. I, chap. i. + +1900. MINCHIN, Sponges--Phylum Porifera in Lankester's "Treatise on +Zoology," ii. + +1905. KUEKENTHAL, W., Leitfaden fuer das Zoologische Praktikum (3rd Ed., +Jena), 2. Kursus: Porifera, Schwaemme, p. 31. + +1906. SOLLAS, I. B. J., Cambridge Natural History--I. Porifera +(Sponges). + +1909. WELTNER, "Spongillidae, Suesswasserschwaemme," in Brauer's "Die +Suesswasserfauna Deutschlands," Heft xix, pp. 177-190. + +1910. LLOYD, An Introduction to Biology for Students in India. + +(b) _Special Memoirs on Anatomy, Physiology, and Development._ + +1844. LAURENT, "Recherches sur l'Hydre et l'Eponge d'eau douce," Voyage +de la Bonite, ii, pp. 113-276. + +1854. CARTER, "Zoosperms in _Spongilla_," Ann. Nat. Hist. (2) xiv, pp. +334-336, pl. xi, figs. 1-6. + +1857. CARTER, "On the ultimate structure of _Spongilla_, and additional +notes on Freshwater Infusoria," Ann. Nat. Hist. (2) xx, pp. 21-41, pl. +i, figs. 1-11. + +1859. CARTER, "On the identity in structure and composition of the +so-called 'seed-like body' of _Spongilla_ with the winter-egg of the +Bryozoa, and the presence of starch-granules in each," Ann. Nat. Hist. +(3) iii, pp. 331-343, pl. viii. + +1859. LIEBERKUEHN, "Neue Beitraege zur Anatomie der Spongien," Arch. Anat. +Phys. J. Mueller, pp. 374-375, 526-528. + +1871. CARTER, "Discovery of the animal of the Spongiadae confirmed," Ann. +Nat. Hist. (4) vii, p. 445. + +1871. HAECKEL, "Ueber die sexuelle Fortpflanzung und das natuerliche +System der Schwaemme," Jenaische Zeitschr. f. Naturw. vi, pp. 643, 645. + +1874. CARTER, "On the nature of the seed-like body of _Spongilla_; on +the origin of the mother-cell of the spicule; and on the presence of +spermatozoa in the _Spongida_," Ann. Nat. Hist. (4) xiv, pp. 97-111. + +1874. LANKESTER, E. RAY, "The mode of occurrence of chlorophyll in +_Spongilla_," Q. J. Micr. Sci. xiv, pp. 400-401. + +1875. SORBY, H., "On the Chromatological relations of _Spongilla +fluviatilis_," Q. J. Micr. Sci. xv, pp. 47-52. + +1878. GANIN, "Zur Entwickelung der _Spongilla fluviatilis_," Zool. Anz. +I, pp. 195-199. + +1882. CARTER, "Spermatozoa, polygonal cell-structure, and the green +colour in _Spongilla_, together with a new species," Ann. Nat. Hist. (5) +x, pp. 362-372, pl. 16. + +1882. GEDDES, "Further researches on animals containing chlorophyll," +Nature, xxv, pp. 303-305, 361-362. + +1882. LANKESTER, E. RAY, "On the chlorophyll-corpuscles and amyloid +deposits of _Spongilla_ and _Hydra_," Q. J. Micr. Sci. xxii (n. s.), pp. +229-254, pl. xx. + +1883. MARSHALL, W., "Einige vorlaeutige Bemerkungen ueber die Gemmulae der +Suesswasserschwaemme," Zool. Anz. vi, pp. 630-634, 648-652. + +1884. CARTER, "The branched and unbranched forms of the Freshwater +Sponges considered generally," Ann. Nat. Hist. (5) xiii, pp. 269-273. + +1884. MARSHALL, W., "Vorlaeutige Bemerkungen ueber die +Fortpflanzungsverhaeltnisse von _Spongilla lacustris_," Ber. Naturf. Ges. +Leipzig,* pp. 22-29. + +1884. POTTS, "Freshwater Sponges as improbable causes of the pollution +of river-water," P. Ac. Philad. pp. 28-30. + +1885. SCHULZE, F. E., "Ueber das Verhaeltniss der Spongien zu den +Choanoflagellaten," SB. preuss. Akad. Wiss. Berlin, pp. 179-191. + +1886. GOETTE, Untersuchungen zur Entwickelungsgeschichte von _Spongilla +fluviatilis_*, Hamburg und Leipzig (5 plates). + +1886. WIERZEJSKI, "Le developpement des Gemmules des Eponges d'eau douce +d'Europe," Arch. Slaves Biologie, i, pp. 26-47 (1 plate). + +1887. CARTER, "On the reproductive elements of the _Spongida_," Ann. +Nat. Hist. (5) xix, pp. 350-360. + +1889. MAAS, "Zur Metamorphose der Spongillalarve," Zool. Anz. xii, pp. +483-487. + +1890. MAAS, "Ueber die Entwickelung des Suesswasserschwaemmes," Zeitschr. +Wiss. Zool. 1, pp. 527-554, pls. xxii, xxiii. + +1890. WEBER, M. et Mme. A., "Quelques nouveau cas de Symbiose," Zool. +Ergebn. einer Reise Niederlaend. Ost-Indien, i, pp. 48-72, pl. v. + +1892. ZYKOFF, "Die Entwicklung der Gemmulae der _Ephydatia fluviatilis_ +auct.," Zool. Anz. xv, pp. 95-96. + +1892. ZYKOFF, "Die Bildung der Gemmulae bei _Ephydatia Fluviatilis_," Revue +Sc. Nat. Soc. St. Petersbourg,* pp. 342-344. + +1892. ZYKOFF, "Die Entwicklung der Gemmulae bei _Ephydatia fluviatilis_ +auct.," Bull. Soc. Imp. Natur. Moscou, n. s. vi, pp. 1-16, pl. i, ii. + +1892. ZYKOFF, "Entwickelungsgeschichte von _Ephydatia muelleri_, Liebk. +aus den Gemmulae," Biol. Centralbl. xii, pp. 713-716. + +1893. WELTNER, "Spongillidenstudien, II," Arch. Naturg. Berlin, lix (1), +pp. 245-282, pls. viii, ix. + +1899. EVANS, R., "The structure and metamorphosis of the larva of +_Spongilla lacustris_," Q. J. Micr. Sci. xlii, pp. 363-476, pls. +xxxv-xli. + +1901. EVANS, R., "A description of _Ephydatia blembingia_, with an +account of the formation and structure of the gemmule," Q. J. Micr. Sci. +xliv, pp. 71-109, pls. i-iv. + +1907. WELTNER, "Spongillideustudien, V.: Zur Biologie von _Ephydatia +fluviatilis_ and die Bedeutung der Amoebocyten fuer die Spongilliden," +Arch. Naturg. Berlin, lxxiii (i), pp. 273-286. + +1907. ANNANDALE, "The buds of _Spongilla proliferens_, Annand.," Rec. +Ind. Mus. i, pp. 267, 268. + +1907. ANNANDALE, "Embryos of _Ephydatia blembingia_, Evans," _ibid._ p. +269. + +1907. ANNANDALE, "The nature of the pores in _Spongilla_," _ibid._ pp. +270-271. + +(c) _Descriptions of Asiatic Species[V] and of Animals associated with +them._ + + [Footnote V: Descriptions of Siberian sponges are not + included in these references.] + +1847-1848. CARTER, "Notes on the species, structure, and animality of +the Freshwater Sponges in the tanks of Bombay (Genus _Spongilla_)," +Trans. Bombay Med. & Phys. Soc., 1847, and Ann. Nat. Hist. (2) i, pp. +303-311, 1848. + +1849. CARTER, "A descriptive account of the Freshwater Sponges (Genus +_Spongilla_) in the Island of Bombay, with observations on their +structure and development," Ann. Nat. Hist. (2) iv, pp. 81-100, pls. +iii-v. + +1868. MARTENS, E. VON, "Ueber einige oestasiatische Suesswasserthiere," +Arch. Naturg. Berlin, xxxiv, pp. 1-67: IV., Ein Suesswasserschwamm aus +Borneo, pp. 61-64, pl. i, fig. 1. + +1881. CARTER, "On _Spongilla cinerea_," Ann. Nat. Hist. (5) vii, p. 263. + +1890. WEBER, M., "Zoologische Ergebnisse einer Reise in Niederlaendisch +Ost-Indien," i, pp. 30-47, pl. iv. + +1901. EVANS, R., "A description of _Ephydatia blembingia_, with an +account of the formation and structure of the gemmule," Q. J. Micr. Sci. +xliv, pp. 71-109, pls. i-iv. + +1901. WELTNER, "Suesswasserspongien von Celebes (Spongillidenstudien, +IV.)," Arch. Naturg. Berlin, lxvii (1) (Special Number), pp. 187-204, +pls. vi, vii. + +1906. ANNANDALE, "A variety of _Spongilla lacustris_ from brackish water +in Bengal," J. As. Soc. Bengal, (n. s.) ii, pp. 55-58. + +1906. ANNANDALE, "Some animals found associated with _Spongilla carteri_ +in Calcutta," _ibid._ pp. 187-196. + +1907. WILLEY, "Freshwater Sponge and Hydra in Ceylon," Spolia Zeylanica, +iv, pp. 184-185. + +1907. ANNANDALE, "On Freshwater Sponges from Calcutta and the +Himalayas," J. As. Soc. Bengal, (n. s.) iii, pp. 15-26. + +1907. ANNANDALE, "Gemmules of _Trochospongilla phillottiana_, Annand.," +Rec. Ind. Mus. i, p. 269. + +1907. ANNANDALE, "Description of two new Freshwater Sponges from Eastern +Bengal, with remarks on allied forms," _ibid._ pp. 387-392. + +1908. ANNANDALE, "Preliminary notice of a collection of Sponges from W. +India, with descriptions of two new species," Rec. Ind. Mus. ii, pp. +25-28. + +1908. KIRKPATRICK, "Description of a new variety of _Spongilla +loricata_, Weltner," _ibid._ pp. 97-99. + +1908. ANNANDALE, "Preliminary notice of a collection of Sponges from +Burma, with the description of a new species of _Tubella_," _ibid._ pp. +157-158. + +1909. ANNANDALE, "Report on a small collection of Sponges from +Travancore," Rec. Ind. Mus. iii, pp. 101-104, pl. xii. + +1909. NEEDHAM, "Notes on the Neuroptera in the collection of the Indian +Museum," _ibid._ pp. 206-207. + +1909. ANNANDALE, "Description of a new species of _Spongilla_ from +Orissa," _ibid._ p. 275. + +1909. ANNANDALE, "Beitraege zur Kenntnis der Fauna von Sued-Afrika: IX. +Freshwater Sponges," Zool. Jahrb. (Syst.) xxvii, pp. 559-568. + +1909. ANNANDALE, "Report on a collection of Freshwater Sponges from +Japan," Annot. Zool. Japon, vii, pp. 105-112, pl. ii. + +1909. ANNANDALE, "Freshwater Sponges in the collection of the United +States National Museum: Part I. Specimens from the Philippines and +Australia," P. U.S. Mus. xxxvi, pp. 627-632. + +1909. ANNANDALE, "Freshwater Sponges collected in the Philippines by the +'Albatross' Expedition," _ibid._ xxxvii, pp. 131-132. + +1909. ANNANDALE, "Freshwater Sponges in the collection of the United +States National Museum: Part II. Specimens from North and South +America," _ibid._ pp. 401-406. + +1910. ANNANDALE, "Freshwater Sponges in the collection of the United +States National Museum: Part III. Description of a new species of +_Spongilla_ from China," _ibid._ xxxviii, p. 183. + +1910. ANNANDALE, "Description of a new species of Sponge from Cape +Comorin," Rec. Ind. Mus. v, p. 31. + +1910. STEPHENSON, "On some aquatic Oligochaete worms commensal in +_Spongilla carteri_," _ibid._ pp. 233-240. + +1910. ANNANDALE, "Note on a Freshwater Sponge and Polyzoon from Ceylon," +Spolia Zeylanica, vii. p. 63, pl. i. + + + + +GLOSSARY OF TECHNICAL TERMS USED IN PART I. + + + _Amphioxi_ (adj. Rod-like spicules sharp at both ends. + _amphioxous_) + + _Amphistrongyli_ (adj. Rod-like spicules blunt at both ends. + _amphistrongylous_) + + _Basal membrane_ A horny, structureless membrane found + at the base of some sponges. + + _Birotulate_ (subst. or adj.) Spicule with a transverse disk at both + ends. + + _Bubble-cells_ Spherical cells of the parenchyma the + contents of which consist of a drop of + liquid covered by a thin film of + protoplasm. + + _Ciliated_ (or _flagellated_) A cavity lined with collar-cells. + _chamber_ + + _Collar-cell_ (_choanocyte_) Cell provided at one end with a + membranous collar and a vibratile lash + or flagellum that springs from within + the collar. + + _Derma_ or _ectodermal layer_ A layer of flat cells arranged like a + pavement on the surface of the sponge. + + _Exhalent_ (or _efferent_) A tubular canal through which water + _canal_ passes from a ciliated chamber towards + the osculum. + + _Fibres_ (skeleton) Thread-like structures that compose the + skeleton of the sponge and are formed + (in the Spongillidae) mainly of + overlapping spicules. + + _Flesh-spicules_ Microscleres (_q. v._) that lie free in + the parenchyma and the derma. + + _Foramen_ An orifice of the gemmule. + + _Foraminal tubule_ A horny tube that surrounds the foramina + of some gemmules. + + _Gemmule_ A mass of cells packed with food-material, + surrounded by at least one horny coat, + capable of retaining vitality in + unfavourable conditions and finally of + giving origin to a new sponge. + + _Green corpuscles_ Minute green bodies found inside cells + of sponges and other animals and + representing a stage in the life-history + of an alga (_Chlorella_). + + _Inhalent_ (or _afferent_) A tubular canal through which water + canal passes from the exterior towards a + ciliated chamber. + + _Megascleres_ The larger spicules that (in the + Spongillidae) form the basis of the + skeleton of the sponge. + + _Microscleres_ Smaller spicules that lie free in the + substance or the derma of the sponge, or + are associated with the gemmule. + + _Monaxon_ (Of spicules) having a single main axis; + (of sponges) possessing skeleton spicules + of this type. + + _Osculum_ An aperture through which water is + ejected from the sponge. + + _Oscular collar_ A ring-shaped membrane formed by an + extension of the derma round an osculum. + + _Parenchyma_ The gelatinous part of the sponge. + + _Pavement layer_ Adherent gemmules arranged close together + in a single layer at the base of a sponge. + + _Pneumatic coat_ A horny or chitinous layer on the surface + of the gemmule containing air-spaces. + If these spaces are of regular form and + arrangement it is said to be _cellular_; + if they are minute and irregular it is + called _granular_. + + _Pore_ A minute hole through which water is + taken into the sponge. + + _Pore-cell_ (_porocyte_) A cell pierced by a pore. + + _Radiating fibres_ Fibres in the skeleton of a sponge that + are vertical or radiate from its centre. + + _Rotula_ A transverse disk borne by a microsclere. + + _Rotulate_ (subst. or adj.) Spicule bearing one or two transverse + disks. + + _Spicule_ A minute mineral body of regular and + definite shape due not to the forces of + crystallization but to the activity of + the living cell or cells in which it is + formed. + + _Spongin_ The horny substance found in the skeletal + framework and the coverings of gemmules + of sponges. Structures formed of + this substance are often referred to as + _chitinous_. + + _Subdermal cavity_ A cavity immediately below the derma + (_q. v._). + + _Transverse fibres_ Fibres in the skeleton of a sponge that + run across between the radiating fibres. + + _Tubelliform_ (of spicule) Having a straight shaft with a transverse + disk at one end and a comparatively + small knob-like projection at the other. + + + + +SYSTEMATIC LIST OF THE INDIAN SPONGILLIDAE. + + +[Types, schizotypes, or cotypes have been examined in the case of all +species, &c., whose names are marked thus, *.] + + Genus 1. SPONGILLA, Lamarck (1816). + Subgenus A. EUSPONGILLA, Vejdovsky (1883). + 1. ? _S. lacustris_, auct. (perhaps in N.W. India). + 1_a_. _S. lacustris_ subsp. _reticulata_*, Annandale (1907). + 2. _S. proliferens_*, Annandale (1907). + 3. _S. alba_*, Carter (1849). + 3_a_. _S. alba_ var. _cerebellata_, Bowerbank (1863). + 3_b_. _S. alba_ var. _bengalensis_*, Annandale (1906). + 4. _S. cinerea_*, Carter (1849). + 5. _S. travancorica_*, Annandale (1909). + 6. _S. hemephydatia_*, Annandale (1909). + 7. _S. crateriformis_* (Potts) (1882). + Subgenus B. EUNAPIUS, J. E. Gray (1867). + 8_a_. _S. carteri_ var. _mollis_*, nov. + 8_b_. _S. carteri_ var. _cava_*, nov. + 8_c_. _S. carteri_ var. _lobosa_*, nov. + 9_a_. _S. fragilis_ subsp. _calcuttana_*, nov. + 9_b_. _S. fragilis_ var. _decipiens_, Weber (probably Malaysian, + not Indian). + 10. _S. gemina_*, sp. nov. + 11. _S. crassissima_*, Annandale (1907). + 11_a_. _S. crassissima_ var. _crassior_*, Annandale (1907). + Subgenus C. STRATOSPONGILLA, Annandale (1909). + 12. _S. indica_*, Annandale (1908). + 13. _S. bombayensis_*, Carter (1882). + 14. _S. ultima_*, Annandale (1910). + + Genus 2. PECTISPONGILLA, Annandale (1909). + 15. _P. aurea_*, Annandale (1909). + 15_a_. _P. aurea_ var. _subspinosa_*, nov. + + Genus 3. EPHYDATIA, Lamouroux (1816). + 16. _E. meyeni_* (Carter) (1849). + + Genus 4. DOSILIA, J. E. Gray (1867). + 17. _D. plumosa_* (Carter) (1849). + + Genus 5. TROCHOSPONGILLA, Vejdovsky (1883). + 18. _T. latouchiana_*, Annandale (1907). + 19. _T. phillottiana_*, Annandale (1907). + 20. _T. pennsylvanica_* (Potts) (1882). + + Genus 6. TUBELLA, Carter (1881). + 21. _T. vesparioides_*, Annandale (1908). + + Genus 7. CORVOSPONGILLA, nov. + 22. _C. burmanica_* (Kirkpatrick) (1908). + 23. _C. lapidosa_* (Annandale) (1908). + + +Order HALICHONDRINA. + + +Siliceous monaxon sponges in which the horny skeleton is much reduced or +absent and the spicular skeleton is more or less definitely reticulate. +The microscleres are usually rod-like and rarely have more than one main +axis. + + +Family SPONGILLIDAE. + +SPONGILLADAE, J. E. Gray, P. Zool. Soc. London, 1867, p. 550. + +Freshwater Halichondrina which at certain seasons produce gemmules armed +with peculiar microscleres. Two distinct kinds of microsclere are often +present, that associated with the gemmule sometimes consisting of a +vertical shaft at the ends of which transverse disks or rotulae are +borne. There is always at least a trace of a subdermal cavity. + +Many authors divide the Spongillidae into two subfamilies:--Spongillinae +(or Euspongillinae), in which the gemmule-spicules have no transverse +rotulae, and Meyeninae (or Ephydatiinae), in which they have rotules at one +or both ends. So gradual, however, is the transition that I find it +difficult to decide in one instance to which of two genera, typical +respectively of the two "subfamilies," a species should be assigned. +Minchin in his account of the Porifera in Lankester's "Treatise on +Zoology" (1900) regards the Spongillidae merely as a subfamily of the +Heterorrhaphidae, and there certainly are few differences of a definite +nature between them and the marine family (or subfamily) Remeridae. + + + _Key to the Indian Genera of_ Spongillidae. + + I. Microscleres without transverse disks. + A. Microscleres of the parenchyma similar + in general structure to those or the + gemmule; the latter without comb-like + vertical rows of spines at the ends SPONGILLA, p. 67. + B. Microscleres of the gemmule with comb-like + vertical rows of spines at both ends PECTISPONGILLA, p. 106. + + II. Some or all of the microscleres birotulate. + (Birotulate microscleres of one kind only.) + A. Microscleres of the gemmule birotulate, the + rotules with serrated or strongly sinuous + edges; parenchyma spicules usually absent, + never of complicated structure EPHYDATIA, p. 108. + B. Microscleres of the gemmule as in + _Ephydatia_; microscleres of the parenchyma + consisting of numerous shafts + meeting in different planes in a central + nodule DOSILIA, p. 110. + C. Microscleres as in _Ephydatia_ except + that the rotulae of the gemmule-spicules + have smooth edges TROCHOSPONGILLA, p. 113. + D. Microscleres of the gemmule without a + trace of rotules, those of the parenchyma + birotulate CORVOSPONGILLA, nov., p. 122. + + III. Microscleres of the gemmule with a well-developed + basal rotule and a vertical shaft + ending above in a mere knob. TUBELLA, p. 120. + +The most distinct genus of Spongillidae not yet found in India is +_Heteromeyenia_, Potts. It is easily distinguished from all others by +the fact that the birotulate spicules of the gemmule are of two quite +distinct kinds, which occur together on every mature gemmule. +_Heteromeyenia_ is represented by several American species, one of which +has been found in Europe. _Acalle_, J. E. Gray, which is represented by +a single South American species (_Spongilla recurvata_, Bowerbank), is +related to _Heteromeyenia_ but has one kind of gemmule-spicule +tubelliform, the other birotulate. Probably _Uraguaya_, Carter, should +be regarded as a subgenus of _Trochospongilla_ with an unusually solid +skeleton; it is peculiar to S. America. _Parmula_, Carter (=_Drulia_, +Gray) includes South American forms allied to _Tubella_, but with the +shaft of the gemmule-spicule degenerate and consisting of a mere +projection in the centre of a shield-like body, which represents the +lower rotule. The status of _Potamolepis_, Marshall, originally +described from the Lake of Galilee, is very doubtful; possibly some or +all of its species belong to the subgenus of _Spongilla_ here called +_Stratospongilla_ (p. 100); but they are stated never to produce +gemmules. The same is the case as regards _Pachydictyum_, Weltner, which +consists of a single species from Celebes. + +The sponges from Lake Baikal assigned by Weltner (Arch. Naturg. lxi (i) +p. 131) to the subfamily Lubomirskinae are of doubtful position and need +not be considered here; while _Lessepsia_, Keller, from one of the salt +lakes on the Suez Canal, certainly does not belong to the family, +although it is assigned to it by von Lendenfeld (Mon. Horny Sponges, p. +904 (1889)) and subsequently by Minchin (Porifera, p. 152, in +Lankester's Treatise on Zoology, part ii (1900)). + + +Genus 1. SPONGILLA, _Lamarck_ (Carter _emend._). + + _Spongilla_, Lamarck, Histoire des Animaux sans Vertebres, ii, p. 111 + (1836). + _Spongilla_, Carter, Ann. Nat. Hist. (5) vii, p. 86 (1881). + _Euspongilla_, Vejdovsky, Abh. Boehm. Ges. xii, p. 15 (1883). + _Spongilla_, Potts, P. Ac. Philad. 1887, p. 182. + +TYPE, _Spongilla lacustris_, auctorum. + +Spongillidae in which the gemmules have (normally) cylindrical or +subcylindrical spicules that are sharp or blunt at the ends, without a +distinct transverse disk or disks and without comb-like vertical rows of +spines. + +The skeleton is variable in structure, sometimes being almost amorphous, +sometimes having well-defined radiating and transverse fibres firmly +compacted with spongin. The skeleton-spicules are either sharp or blunt +at the ends. Flesh-spicules are often absent; when present they are +needle-like and resemble the gemmule-spicules in general structure; they +have not even rudimentary rotules at their ends. The gemmules either lie +free in the substance of the sponge or are attached to its support; +sometimes they adhere together in free or attached groups. + +_Spongilla_ is undoubtedly the most primitive genus of the Spongillidae, +its spicules showing less sign of specialization than those of any other +genus included in the family. As a fossil it goes back at any rate to +the Upper Jurassic (p. 52). + +GEOGRAPHICAL DISTRIBUTION.--Cosmopolitan. In most countries the majority +of the freshwater sponges belong to this genus, but in Japan _Ephydatia_ +seems to predominate. + + +_Key to the Indian Species of_ Spongilla. + + I. Gemmule provided with a thick, apparently + granular pneumatic coat in + which the gemmule-spicules are arranged + tangentially or vertically. (Subgenus + _Euspongilla_, p. 69.) + A. No foraminal tubule. + _a._ Sponge bright green, soft and + compressiblewhen fresh, very fragile + dry _lacustris_, p. 69. + _a'._ Sponge white or grey, hard both + fresh and dry _alba_, p. 76. + B. A foraminal tubule present. + _b._ Skeleton-spicules smooth. + beta. Gemmules free; gemmule-spicules + arranged tangentially and + horizontally _proliferens_, p. 72. + beta'. Gemmules free; gemmule-spicules + arranged vertically or nearly + so in a single series _hemephydatia_, p. 82. + beta''. Gemmules firmly fixed + to the support of the sponge; + gemmule-spicules almost vertical, + irregularly arranged, as a rule in + more than one series _travancorica_, p. 81. + _b'._ Skeleton-spicules spiny or + irregular in outline. + beta'''. Gemmule-spicules tangential + and horizontal, without + rudimentary rotules _cinerea_, p. 79. + beta''''. Gemmule-spicules vertical or + nearly so, often with + rudimentary rotules at the tips _crateriformis_, p. 83. + + II. Gemmules surrounded in several layers + by distinct polygonal air-spaces with + chitinous walls. (Subgenus _Eunapius_, + p. 86.) + A. Gemmules single. Skeleton- and + gemmule-spicules smooth, pointed, + not very stout _carteri_, p. 87. + B. Gemmules bound together in pairs. + Skeleton friable; skeleton-spicules + slender _gemina_, nov., p. 97. + C. Gemmules bound together in free + groups of more than two or forming + a "pavement-layer" at the base of + the sponge. + _c._ Skeleton friable; + skeleton-spicules slender _fragilis_, p. 95. + _c'._ Skeleton very hard and + resistant; skeleton-spicules stout _crassissima_, p. 98. + + III. Gemmules without or with irregular + pneumatic coat, covered by a chitinous + membrane or membranes in which the + gemmule-spicules lie parallel to the + surface. (Subgenus _Stratospongilla_, + p. 100.) + + A. Skeleton spicules spiny or irregular in + outline. + + _a._ Skeleton-spicules blunt; gemmules + covered by a single chitinous + membrane _indica_, p. 100. + + _a'._ Skeleton-spicules sharp; gemmules + covered by two chitinous membranes _bombayensis_, p. 102. + + B. Skeleton-spicules smooth. + Skeleton-spicules sharp; gemmule + spicules very irregular in form _ultima_, p. 104. + + +Subgenus A. EUSPONGILLA, _Vejdovsky_. + + _Euspongilla_, Vejdovsky, Abh. Boehm. Ges. xii, p. 15 (1883). + _Euspongilla_, _id._, in Potts's "Fresh-Water Sponges," P. Ac. Philad. + 1887, p. 172. + _Euspongilla_, Weltner, in Zacharias's Tier- und Pflanzenwelt des + Suesswassers, i, p. 210 (1891). + +TYPE, _Spongilla lacustris_, auctorum. + +Spongillae in which the gemmules are covered with a thick, apparently +granular pneumatic coat. A delicate membrane often occurs outside this +coat, but it is never thick or horny. The gemmules usually lie free in +the sponge but sometimes adhere to its support; rarely they are fastened +together in groups (_e. g._ in _S. aspinosa_, Potts). The +skeleton-spicules are never very stout and the skeleton is always +delicate. + +The species in this subgenus are closely allied and must be +distinguished rather by the sum of their peculiarities than by any one +character. They occur in all countries in which Spongillidae are found. +Seven Indian species may be recognized. + + +1. Spongilla lacustris, _auctorum_. + + _Spongilla lacustris_, Bowerbank, P. Zool. Soc. London, 1863, p. 441, + pl. xxxviii, fig. 14. + _Spongilla lacustris_, Carter, Ann. Nat. Hist. (5) vii, p. 87 (1881). + _Euspongilla lacustris_, Vejdovsky, in Potts's "Fresh-Water Sponges," + P. Ac. Philad. 1887, p. 172. + _Spongilla lacustris_, Potts, _ibid._, p. 186, pl. v, fig. 1, pl. vii, + figs. 1-6. + _Euspongilla lacustris_, Weltner, in Zacharias's Tier- und Pflanzenwelt + des Suesswassers, i, p. 211, figs. 36-38 (1891). + _Spongilla lacustris_, _id._, Arch. Naturg. lxi (i), pp. 118, 133-135 + (1895). + _Spongilla lacustris_, Annandale, J. Linn. Soc., Zool., xxx, p. 245 + (1908). + + [I have not attempted to give a detailed synonymy of this + common species. There is no means of telling whether many of + the earlier names given to forms or allies of _S. lacustris_ + are actual synonyms, and it would serve no useful purpose, + so far as the fauna of India is concerned, to complicate + matters by referring to obscure descriptions or possible + descriptions of a species only represented in India, so far + as we know, by a specialized local race, to which separate + references are given.] + +_Sponge_ soft and easily compressed, very brittle when dry, usually +consisting of a flat or rounded basal portion of no great depth and of +long free cylindrical branches, which droop when removed from the water; +branches occasionally absent. Colour bright green when the sponge is +growing in a strong light, dirty flesh-colour when it is growing in the +shade. (Even in the latter case traces of the "green corpuscles" can be +detected in the cells of the parenchyma.) Oscula star-shaped, of +moderate size, as a rule rendered conspicuous by the furrows that +radiate from them over the outer surface of the parenchyma below the +external membrane; oscular collars well developed. + +_Skeleton_ reticulate, loose, with definite radiating and transverse +fibres held together by a small quantity of spongin; the fibres slender +but not extremely so. + +_Spicules._ Skeleton-spicules smooth, sharply pointed, long, slender. +Flesh-spicules slender, covered with small spines, sharply pointed, +nearly straight. Gemmule-spicules resembling the flesh-spicules but +shorter and as a rule more strongly curved, sometimes bent so as to form +semicircular figures, usually pointed somewhat abruptly; their spines +relatively longer than those of the flesh-spicules, often curved +backwards, especially near the ends of the spicules, at which points +they are often longer than elsewhere. + +_Gemmules_ usually numerous in autumn, lying free in the sponge, +spherical, variable in size but usually rather large, as a rule covered +with a thick granular coat in which the spicules are arranged +tangentially; a horizontal layer of spicules often present in the +external membrane; the granular coat and its spicules occasionally +deficient. No foraminal tubule; its place sometimes taken by an open, +bowl-shaped chitinous structure the base of which is in continuity with +the inner chitinous coat of the gemmule. + +_S. lacustris_ is an extremely variable species, varying in the size, +proportions and shape of its spicules, in its external form and in the +size and structure of the gemmule. A considerable number of varieties +have been described from different parts of Europe and N. America, but +some of these may represent distinct but closely-allied species; +descriptions of most of them will be found in Potts's "Fresh-Water +Sponges." The embryology and the earlier stages of the development from +the egg have been described in great detail by Evans (Quart. J. Micr. +Sci. (n. s.) xlii, p. 363 (1899)), while the anatomy and physiology are +discussed by most authors who have written on these features in the +Spongillidae. + +TYPE.--It is impossible to say who was the first authority to use the +name _Spongilla lacustris_ in the sense in which it is used by recent +authors. No type can therefore be recognized. + +GEOGRAPHICAL DISTRIBUTION.--_S. lacustris_ occurs all over Europe and N. +America and is probably the commonest species in most parts of both +continents. It has also been found in Northern Asia and may occur in the +Himalayan lakes and in the north-west of India. + + +1 _a._ Subspecies reticulata*, _Annandale_. + + _Spongilla reticulata_, Annandale, Rec. Ind. Mus. i, p. 387, + pl. xiv, fig. 1 (1907). + + _Spongilla lacustris_ subspecies _reticulata_, _id._, P. + U.S. Mus. xxxvii, p. 401 (1909). + +This race differs from the typical _S. lacustris_ in the following +particulars:-- + + (1) The branches are always compressed and anastomose + freely when well developed (fig. 5, p. 37); + + (2) the skeleton-fibres are finer; + + (3) the skeleton-spicules are longer; + + (4) the gemmule-spicules are longer and more slender and are + never strongly bent. + +[Illustration: Fig. 8. + +A=gemmule-spicules of _Spongilla lacustris_ subsp. _reticulata_ (from +type); B=gemmule-spicules of _S. alba_ from Calcutta: both highly +magnified.] + +As regards the form of the skeleton- and gemmule-spicules and also that +of the branches the subspecies _reticulata_ resembles _S. alba_ rather +than _S. lacustris_, but owing to the fact that it agrees with _S. +lacustris_ in its profuse production of branches, in possessing green +corpuscles and in its fragility, I think it should be associated with +that species. + +The branches are sometimes broad (fig. 5, p. 37), sometimes very +slender. In the latter condition they resemble blades of grass growing +in the water. + +TYPE in the Indian Museum; a co-type in the British Museum. + +GEOGRAPHICAL DISTRIBUTION.--All over Eastern India and Burma; also in +the Bombay Presidency. _Localities:_--BENGAL, Port Canning, Ganges +delta; Rajshahi (Rampur Bhulia) on the Ganges, 150 miles N. of Calcutta +(_Annandale_); Puri district, Orissa (_Annandale_); R. Jharai, Siripur, +Saran district, Tirhut (_M. Mackenzie_): MADRAS PRESIDENCY, Madras +(town) (_J. R. Henderson_): BOMBAY PRESIDENCY, Igatpuri, W. Ghats +(_Annandale_). + +BIOLOGY.--This subspecies is usually found in small masses of water, +especially in pools of rain-water, but Mr. Mackenzie found it growing +luxuriantly in the Jharai at a time of flood in September. It is very +abundant in small pools among the sand-dunes that skirt the greater part +of the east coast of India. Here it grows with great rapidity during the +"rains," and often becomes desiccated even more rapidly as soon as the +rain ceases. As early in the autumn as October I have seen masses of the +sponge attached, perfectly dry, to grass growing in the sand near the +Sur Lake in Orissa. They were, of course, dead but preserved a life-like +appearance. Some of them measured about six inches in diameter. At Port +Canning the sponge grows during the rains on the brickwork of bridges +over ditches of brackish water that dry up at the beginning of winter, +while at Rajshahi and at Igatpuri I found it at the edges of small +ponds, at the latter place in November, at the former in February. +Specimens taken at Madras by Dr. Henderson during the rains in small +ponds in the sand contained no gemmules, but these structures are very +numerous in sponges examined in autumn or winter. + +Numerous larvae of _Sisyra indica_ (p. 92) were found in this sponge at +Rajshahi. Unlike those obtained from _S. alba_, they had a green colour +owing to the green matter sucked from the sponge in their stomachs. The +_coralloides_ phase of _Plumatella fruticosa_ (p. 219) was also found in +_S. lacustris_ subsp. _reticulata_ at Rajshahi. + +So far as my experience goes, this subspecies has always a bright green +colour due to the presence of "green corpuscles," even when it is +growing in a pond heavily shaded by trees or under the arch of a small +bridge. Probably the more intense light of India enables the corpuscles +to flourish in situations in which in Europe they would lose their +chlorophyll. + + +2. Spongilla proliferens*, _Annandale_. + + _Spongilla cinerea_, Weber (_nec_ Carter), Zool. Ergeb. + Niederl. Ost-Ind. vol. i, pp. 35, 46 (1890). + + _Spongilla proliferens_, Annandale, J. Asiat. Soc. Bengal, + 1907, p. 15, fig. 1. + + _Spongilla proliferens_, _id._, Rec. Ind. Mus. i, pp. 267, + 271 (1907). + +_Sponge_ forming soft, shallow cushions rarely more than 10 cm. in +diameter on the leaves of water-plants, or small irregular masses on +their roots and stems. Colour bright green. Oscula moderate, flat, +surrounded by deep, cone-shaped collars; radiating furrows and canals in +the parenchyma surrounding them often deep. External pores contained +normally in single cells. The surface frequently covered by small +rounded buds; true branches if present more or less flattened or +conical, always short, as a rule absent. + +_Skeleton_ loose, feebly reticulate at the base of the sponge; +transverse fibres slender in the upper part of the sponge, often +scarcely recognizable at its base. Very little spongin present. + +_Spicules._ Skeleton-spicules long, smooth, sharply pointed; the length +on an average at least 20 times the greatest breadth, often more. +Flesh-spicules slender, gradually pointed, nearly straight, covered with +minute straight or nearly straight spines. Gemmule-spicules very +similar, but usually a little stouter and often blunt at the ends; their +spines rather longer than those on the flesh-spicules, usually more +numerous near the ends than in the middle of the spicule, slightly +retroverted, those at the extreme tips often so arranged as to suggest a +rudimentary rotule. + +[Illustration: Fig. 9.--Gemmule of _Spongilla proliferens_ as seen in +optical section (from Calcutta), x 140.] + +_Gemmules_ usually numerous, lying free near the base of the sponge, +very variable in size, spherical, surrounded by a thick granular layer +in which the spicules, which are always very numerous, are arranged +tangentially, their position being more near the vertical than the +horizontal; a few horizontal spicules usually present on the external +surface of the gemmule, which frequently has a ragged appearance owing +to some of the tangential spicules protruding further than others. +Foraminal tubule stout, cylindrical, usually somewhat contorted; its +orifice irregular in outline. Sometimes more than one foramen present. + +_S. proliferens_ can be distinguished from all forms of _S. lacustris_ +and _S. alba_ by the fact that its gemmules possess a foraminal tubule; +from _S. cinerea_ it can be distinguished by its colour and its smooth +skeleton-spicules, and from _S. travancorica_ by its free gemmules. I +have been enabled by the kindness of Prof. Max Weber to examine +specimens from Celebes and Java identified by him as _S. cinerea_, +Carter, and have no doubt that they belong to my species. + +TYPE in the Indian Museum; a co-type in the British Museum. + +GEOGRAPHICAL DISTRIBUTION.--All over Eastern India and Burma; also in +Cochin on the west coast; Ceylon; W. China; Java, Flores and Celebes. +_Localities_:--BENGAL, Calcutta and neighbourhood (_Annandale_); +Berhampore, Murshidabad district (_R. E. Lloyd_): ASSAM, Mangal-dai near +the Bhutan frontier (_S. W. Kemp_): MADRAS PRESIDENCY, Madras (town) and +neighbourhood (_J. R. Henderson_); Rambha, Ganjam district +(_Annandale_); Bangalore, Mysore (alt. _ca._ 3000 ft.) (_Annandale_); +Ernakulam and Trichur, Cochin (_G. Mathai_): BURMA, Rangoon +(_Annandale_, _J. Coggin Brown_); Prome, Upper Burma (_J. Coggin +Brown_); Kawkareik, Amherst district, Tenasserim (_Annandale_): CEYLON, +between Maradankawela and Galapita-Gala, North Central Province +(_Willey_). Mr. J. Coggin Brown has recently brought back specimens from +Yunnan. + +BIOLOGY.--_S. proliferens_ is usually found in ponds which never dry up; +Prof. Max Weber found it in small streams in Malaysia. It is common in +India on the leaves of _Vallisneria_ and _Limnanthemum_, on the roots of +_Pistia stratiotes_ and on the stems of rushes and grass. So far as I +have been able to discover, the life of the individual sponge is short, +only lasting a few weeks. + +Sexual reproduction occurs seldom or never, but reproduction by means of +buds and gemmules continues throughout the year. The former is a rare +method of reproduction in most Spongillidae but in this species occurs +normally and constantly, the buds being often very numerous on the +external surface. They arise a short distance below the surface as +thickenings in the strands of cells that accompany the radiating fibres +of the skeleton. As they grow they push their way up the fibres, forcing +the external membrane outwards. The membrane contracts gradually round +their bases, cuts off communication between them and the parent sponge +and finally sets them adrift. No hole remains when this takes place, for +the membrane closes up both round the base of the bud and over the +aperture whence it has emerged. + +The newly liberated bud already possesses numerous minute pores, but as +yet no osculum; its shape exhibits considerable variation, but the end +that was farthest from the parent-sponge before liberation is always +more or less rounded, while the other end is flat. The size also varies +considerably. Some of the buds float, others sink. Those that float do +so either owing to their shape, which depends on the degree of +development they have reached before liberation, or to the fact that a +bubble of gas is produced in their interior. The latter phenomenon only +occurs when the sun is shining on the sponge at the moment they are set +free, and is due to the action of the chlorophyll of the green bodies so +abundant in certain of the parenchyma cells of this species. If the +liberation of the bud is delayed rather longer than usual, numbers of +flesh-spicules are produced towards the ends of the primary +skeleton-fibres and spread out in one plane so as to have a fan-like +outline; in such buds the form is more flattened and the distal end less +rounded than in others, and the superficial area is relatively great, so +that they float more readily. Those buds that sink usually fall in such +a way that their proximal, flattened end comes in contact with the +bottom or some suspended object, to which it adheres. Sometimes, +however, owing to irregularity of outline in the distal end, the +proximal end is uppermost. In this case it is the distal end that +adheres. Whichever end is uppermost, it is in the uppermost end, or as +it may now be called, the upper surface, that the osculum is formed. +Water is drawn into the young sponge through the pores and, finding no +outlet, accumulates under the external membrane, the subdermal cavity +being at this stage even larger than it is in the adult sponge. +Immediately after adhesion the young sponge flattens itself out. This +process apparently presses together the water in the subdermal cavity +and causes a large part of it to accumulate at one point, which is +usually situated near the centre of the upper surface. A transparent +conical projection formed of the external membrane arises at this point, +and at the tip of the cone a white spot appears. What is the exact cause +of this spot I have not yet been able to ascertain, but it marks the +point at which the imprisoned water breaks through the expanded +membrane, thus forming the first osculum. Before the aperture is formed, +it is already possible to distinguish on the surface of the parenchyma +numerous channels radiating from the point at which the osculum will be +formed to the periphery of the young sponge. These channels as a rule +persist in the adult organism and result from the fact that the inhalent +apertures are situated at the periphery, being absent from both the +proximal and the distal ends of the bud. In the case of floating buds +the course of development is the same, except that the osculum, as in +the case of development from the gemmule in other species (see Zykoff, +Biol. Centrbl. xii, p. 713, 1892), is usually formed before adhesion +takes place. + +The sponge of _S. proliferens_ is usually too small to afford shelter to +other animals, and I have not found in it any of those commonly +associated with _S. carteri_ and _S. alba_. + +Owing to its small size _S. proliferens_ is more easily kept alive in an +aquarium than most species, and its production of buds can be studied in +captivity. In captivity a curious phenomenon is manifested, viz. the +production of extra oscula, often in large numbers. This is due either +to a feebleness in the currents of the sponge which makes it difficult +to get rid of waste substances or to the fact that the canals get +blocked. The effluent water collects in patches under the external +membrane instead of making its way out of the existing oscula, and new +oscula are formed over these patches in much the same way as the first +osculum is formed in the bud. + + +3. Spongilla alba*, _Carter_. + + _Spongilla alba_, Carter, J. Bombay Asiat. Soc. iii, p. 32, + pl. i, fig. 4 & Ann. Nat. Hist. (2) iv, p. 83, pl. iii, fig. + 4 (1849) + + _Spongilla alba_, Bowerbank, P. Zool. Soc. London, 1863, p. + 463 pl. xxxviii, fig. 15. + + _Spongilla alba_, Carter, Ann. Nat. Hist. (5) vii, p. 88 + (1881). + + _Spongilla alba_, Petr, Rozp. Ceske Ak. Praze, Trida, ii, + pl. i, figs. 3-6 (1899) (text in Czech). + + _Spongilla alba_, Annandale, Rec. Ind. Mus. i, p. 388, pl. + xiv, fig. 2 (1907). + +_Sponge_ forming masses of considerable area, but never of more than +moderate depth or thickness. Surface smooth and undulating or with +irregular or conical projections; sponge hard but brittle; colour white +or whitish; oscula of moderate or large size, never very conspicuous; +radiating furrows absent or very short; external membrane adhering to +the substance of the sponge. + +_Skeleton_ forming a moderately dense network of slender radiating and +transverse fibres feebly held together; little spongin present; the +meshes much smaller than in _S. lacustris_ or _S. proliferens_. + +_Spicules._ Skeleton-spicules smooth, sharply pointed, slender, feebly +curved. Gemmule-spicules (fig. 8, p. 71) slender, cylindrical, blunt or +abruptly pointed at the ends, feebly curved, bearing relatively long +backwardly directed spines, which are usually more numerous at the ends +than near the middle of the shaft. Flesh-spicules very numerous in the +parenchyma and especially the external membrane, as a rule considerably +more slender and more sharply pointed than the gemmule-spicules, covered +with straight spines which are often longer at the middle of the shaft +than at the ends. + +_Gemmules_ usually of large size, with a moderately thick granular +layer; spicules never very numerous, often lying horizontally on the +external surface of the gemmule as well as tangentially in the granular +layer; no foraminal tubule; a foraminal cup sometimes present. + + +3_a_. Var. cerebellata, _Bowerbank_. + + _Spongilla cerebellata_, Bowerbank, P. Zool. Soc. London, + 1863, p. 465, pl. xxxviii, fig. 16. + + _Spongilla alba_ var. _cerebellata_, Carter, Ann. Nat. Hist. + (5) vii, p. 88 (1881). + + _Spongilla cerebellata_, Weltner, Arch. Naturg. lxi (i), p. + 117 (1895). + + _Spongilla cerebellata_, Kirkpatrick, Ann. Nat. Hist. (7) + xx, p. 523 (1907). + +This variety is distinguished from the typical form by the total absence +of flesh-spicules. The gemmule-spicules are also more numerous and cross +one another more regularly. + + +3_b_. Var. bengalensis*, _Annandale_. (Plate I, figs. 1-3.) + + _Spongilla lacustris_ var. _bengalensis_, Annandale, J. + Asiat. Soc. Bengal, 1906, p. 56. + + _Spongilla alba_ var. _marina_, _id._, Rec. Ind. Mus. i, p. + 389 (1907). + +The sponge is either devoid of branches or produces irregular, +compressed, and often digitate processes, sometimes of considerable +length and delicacy. Flesh-spicules are usually present throughout the +sponge, but are sometimes absent from one part of a specimen and present +in others. Some of the gemmules are often much smaller than the others. +Perhaps this form should be regarded as a phase rather than a true +variety (see p. 18). + +All forms of _S. alba_ can be distinguished from all forms of _S. +lacustris_ by the much closer network of the skeleton and by the +consequent hardness of the sponge; also by the complete absence of green +corpuscles. + +TYPES. The types of the species and of the var. _cerebellata_ are in the +British Museum, with fragments of the former in the Indian Museum; that +of var. _bengalensis_ is in the Indian Museum, with a co-type in London. + +GEOGRAPHICAL DISTRIBUTION.--India And Egypt. _Localities_:--BOMBAY +PRESIDENCY, island of Bombay (_Carter_); Igatpuri, W. Ghats +(_Annandale_): BENGAL, Calcutta; Port Canning, Ganges delta (var. +_bengalensis_) (_Annandale_); Garia, Salt Lakes, nr. Calcutta (var. +_bengalensis_) (_B. L. Chaudhuri_); Chilka Lake, Orissa (var. +_bengalensis_) (_Gopal Chunder Chatterjee_): MADRAS PRESIDENCY, Rambha, +Ganjam district (_Annandale_): NIZAM'S TERRITORY, Aurangabad +(_Bowerbank_, var. _cerebellata_). The var. _cerebellata_ has also been +taken near Cairo. + +BIOLOGY.--The typical form of the species is usually found growing on +rocks or bricks at the edges of ponds, while the variety _bengalensis_ +abounds on grass-roots in pools and swamps of brackish water in the +Ganges delta and has been found on mussel-shells (_Modiola jenkinsi_, +Preston) in practically salt water in the Chilka Lake. Carter procured +the typical form at Bombay on stones which were only covered for six +months in the year, and "temporarily on floating objects." In Calcutta +this form flourishes in the cold weather on artificial stonework in the +"tanks" together with _S. carteri_, _S. fragilis_, _Ephydatia meyeni_, +and _Trochospongilla latouchiana_. + +The variety _bengalensis_ is best known to me as it occurs in certain +ponds of brackish water at Port Canning on the Mutlah River, which +connects the Salt Lakes near Calcutta with the sea. It appears in these +ponds in great luxuriance every year at the beginning of the cold +weather and often coats the whole edge for a space of several hundred +feet, growing in irregular masses which are more or less fused together +on the roots and stems of a species of grass that flourishes in such +situations. Apparently the tendency for the sponges to form branches is +much more marked in some years than in others (see Pl. I, figs. 1-3). +The gemmules germinate towards the end of the "rains," and large masses +of sponge are not formed much before December. At this season, however, +the level of the water in the ponds sinks considerably and many of the +sponges become dry. If high winds occur, the dry sponges are broken up +and often carried for considerable distances over the flat surrounding +country. In January the gemmules floating on the surface of the ponds +form a regular scum. _S. alba_ var. _bengalensis_ is the only sponge +that occurs in these ponds at Port Canning, but _S. lacustris_, subsp. +_reticulata_, is occasionally found with it on brickwork in the ditches +that drain off the water from the neighbouring fields into the Mutlah +estuary. The latter sponge, however, perishes as these ditches dry up, +at an earlier period than that at which _S. alba_ reaches its maximum +development. + +The larvae of _Sisyra indica_ are commonly found in the oscula of the +typical form of _S. alba_ as well as in those of _S. lacustris_ subsp. +_reticulata_, and _S. carteri_; but the compact structure of the sponge +renders it a less suitable residence for other _incolae_ than _S. +carteri_. + +In the variety _bengalensis_, as it grows in the ponds at Port Canning, +a large number of arthropods, molluscs and other small animals take +shelter. Apart from protozoa and rotifers, which have as yet been little +studied, the following are some of the more abundant inhabitants of the +sponge:--The sea-anemone, _Sagartia schilleriana_ subsp. _exul_ (see p. +140), which frequently occurs in very large numbers in the broader +canals; the free-living nematode, _Oncholaimus indicus_[W], which makes +its way in and out of the oscula; molluscs belonging to several species +of the genus _Corbula_, which conceal themselves in the canals but are +sometimes engulfed in the growing sponge and so perish; young +individuals of the crab _Varuna litterata_, which hide among the +branches and ramifications of the larger sponges together with several +small species of prawns and the schizopod _Macropsis orientalis_[X]; the +peculiar amphipod _Quadrivisio bengalensis_[Y], only known from the +ponds at Port Canning, which breeds in little communities inside the +sponge; a small isopod[Z], allied to _Sphaeroma walkeri_, Stebbing; the +larva of a may-fly, and those of at least two midges (Chironomidae). + + [Footnote W: O. von Linstow, Rec. Ind. Mus. i, p. 45 + (1907).] + + [Footnote X: W. M. Tattersall, _ibid._, ii, p. 236 (1908).] + + [Footnote Y: T. R. R. Stebbing, _ibid._, i, p. 160 (1907); + and N. Annandale, _ibid._, ii, p. 107 (1908).] + + [Footnote Z: Mr. Stebbing has been kind enough to examine + specimens of this isopod, which he will shortly describe in + the Records of the Indian Museum. _S. walkeri_, its nearest + ally, was originally described from the Gulf of Manaar, + where it was taken in a tow-net gathering (see Stebbing in + Herdman's Report on the Ceylon Pearl Fisheries, pt. iv, p. + 31 (1905)).] + +The peculiarly mixed nature (marine and lacustrine) of the fauna +associated with _S. alba_ in the ponds at Port Canning is well +illustrated by this list, and it only remains to be stated that little +fish (_Gobius alcockii_, _Barbus stigma_, _Haplochilus melanostigma_, +_H. panchax_, etc.) are very common and feed readily on injured sponges. +They are apparently unable to attack a sponge so long as its external +membrane is intact, but if this membrane is broken, they swarm round the +sponge and devour the parenchyma greedily. In fresh water one of these +fishes (_Gobius alcockii_, see p. 94) lays its eggs in sponges. + +The chief enemy of the sponges at Port Canning is, however, not an +animal but a plant, viz., a green filamentous alga which grows inside +the sponge, penetrating its substance, blocking up its canals and so +causing it to die. Similar algae have been described as being beneficial +to the sponges in which they grow[AA], but my experience is that they +are deadly enemies, for the growth of such algae is one of the +difficulties which must be fought in keeping sponges alive in an +aquarium. The alga that grows in _S. alba_ often gives it a dark green +colour, which is, however, quite different from the bright green caused +by the presence of green corpuscles. The colour of healthy specimens of +the variety _bengalensis_ is a rather dark grey, which appears to be due +to minute inorganic particles taken into the cells of the parenchyma +from the exceedingly muddy water in which this sponge usually grows. If +the sponge is found in clean water, to whichever variety of the species +it belongs, it is nearly white with a slight yellowish tinge. Even when +the typical form is growing in close proximity to _S. proliferens_, as +is often the case, no trace of green corpuscles is found in its cells. + + [Footnote AA: See M. and A. Weber in M. Weber's Zool. Ergeb. + Niederl. Ost-Ind. vol. i, p. 48, pl. v (1890).] + + +4. Spongilla cinerea*, _Carter_. + + _Spongilla cinerea_, Carter, J. Bombay Soc. iii, p. 30, pl. + i, fig. 5, & Ann. Nat. Hist. (2) iv, p. 82, pl. iii, fig. 5 + (1849). + + _Spongilla cinerea_, Bowerbank, P. Zool. Soc. London, 1863, + p. 468, pl. xxxviii, fig. 19. + + _Spongilla cinerea_, Carter, Ann. Nat. Hist. (5) vii, p. 263 + (1881). + +_Sponge_ forming large, flat sheets, never more than a few millimetres +in thickness, without a trace of branches, compact but very friable, of +a dark greyish colour; oscula small and inconspicuous or moderately +large, never prominent; membrane adhering closely to the sponge. + +_Skeleton_ with well-defined but slender radiating fibres, which contain +very little spongin; transverse fibres close together but consisting for +the most part of one or two spicules only. + +_Spicules._ Skeleton-spicules short, slender, sharply pointed, minutely +serrated or irregular in outline, almost straight. Gemmule-spicules very +small, rather stout, cylindrical, pointed, covered with relatively long +and stout spines which are either straight or directed towards the ends +of the spicule. Flesh-spicules fairly numerous in the external membrane +but by no means abundant in the parenchyma, very slender, gradually +pointed, covered uniformly with minute but distinct spines. + +_Gemmules_ very small, only visible to the naked eye as minute specks, +as a rule numerous, free in the substance of the sponge, each provided +with a slender foraminal tubule and covered with a thick granular coat +in which the gemmule-spicules are arranged almost horizontally; a +horizontal layer of spicules also present on the external surface of the +gemmule; gemmule-spicules very numerous. + +[Illustration: Fig. 10.--Gemmules and fragment of the skeleton of +_Spongilla cinerea_ (from type specimen), x 35.] + +This sponge is easily distinguished from its Indian allies by the form +of its skeleton-spicules, which are, as Bowerbank expresses it, +"subspined"; that it to say, under a high power of the microscope their +outline appears to be very minutely serrated, although under a low power +they seem to be quite smooth. The spicules also are smaller than those +of _S. alba_, the only species with which _S. cinerea_ is likely to be +confused, and the gemmule has a well-developed foraminal tubule; the +skeleton is much closer than in _S. proliferens_. + +TYPE in the British Museum; a piece in the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--_S. cinerea_ is only known from the Bombay +Presidency. Carter obtained the original specimens at Bombay and the +only ones I have found were collected at Nasik, which is situated on the +eastern slopes of the Western Ghats, about 90 miles to the north-east. + +BIOLOGY.--Carter's specimens were growing on gravel, rocks and stones at +the edge of "tanks," and were seldom covered for more than six months in +the year. Mine were on the sides of a stone conduit built to facilitate +bathing by conveying a part of the water of the Godaveri River under a +bridge. They were accompanied by _Spongilla indica_ and _Corvospongilla +lapidosa_ (the only other sponges I have found in running water in +India) and in the month of November appeared to be in active growth. + + +5. Spongilla travancorica*, _Annandale_. + + _Spongilla travancorica_, Annandale, Rec. Ind. Mus. iii, p. + 101, pl. xii, fig. 1 (1909). + +_Sponge_ small, encrusting, without branches, hard but brittle; its +structure somewhat loose; colour dirty white. Dermal membrane in close +contact with the skeleton; pores and oscula inconspicuous. Surface +minutely hispid, smooth and rounded as a whole. + +_Skeleton_ consisting of moderately stout and coherent radiating fibres +and well-defined transverse ones; a number of horizontal megascleres +present at the base and surface, but not arranged in any definite order. +No basal membrane. + +[Illustration: Fig. 11.--Microscleres of _Spongilla travancorica_. + +A=Gemmule-spicules; B=flesh-spicules (from type specimen), x 240.] + +_Spicules._ Skeleton-spicules smooth, pointed at either end, moderately +stout, straight or curved, sometimes angularly bent; curvature usually +slight. Free microscleres abundant in the dermal membrane, slender, +nearly straight, gradually and sharply pointed, profusely ornamented +with short straight spines, which are much more numerous and longer at +the middle than near the ends. Gemmule-spicules stouter and rather +longer, cylindrical, terminating at each end in a sharp spine, +ornamented with shorter spines, which are more numerous and longer at +the ends than at the middle; at the ends they are sometimes directed +backwards, without, however, being curved. + +_Gemmules_ firmly adherent to the support of the sponge, at the base of +which they form a layer one gemmule thick; each provided with at least +one foraminal tubule, which is straight and conical: two tubules, one at +the top and one at one side, usually present. Granular layer well +developed. Spicules arranged irregularly in this layer, as a rule being +more nearly vertical than horizontal but pointing in all directions, not +confined externally by a membrane; no external layer of horizontal +spicules. + + _Measurements of Spicules and Gemmules._ + + Length of skeleton-spicules 0.289-0.374 mm. + Greatest diameter of skeleton-spicules 0.012-0.016 " + Length of free microscleres 0.08-0.096 " + Greatest diameter of free microscleres 0.002 mm. + Length of gemmule-spicules 0.1-0.116 " + Diameter of gemmule-spicule 0.008 mm. + " " gemmule 0.272-0.374 " + +This species is easily distinguished from its allies of the subgenus +_Euspongilla_ by its adherent gemmules with their (usually) multiple +apertures and rough external surface. + +TYPE in the collection of the Indian Museum. + +HABITAT. Backwater near Shasthancottah, Travancore, in slightly brackish +water; on the roots of shrubs growing at the edge; November, 1908 +(_Annandale_). + +The specimens were dead when found. + + +6. Spongilla hemephydatia*, _Annandale_. + + _Spongilla hemephydatia_, Annandale, Rec. Ind. Mus. iii, p. + 275 (1909). + +[Illustration: Fig. 12.--Gemmule and spicules of _Spongilla +hemephydatia_ (from type specimen).] + +_Sponge_ soft, fragile, amorphous, of a dirty yellow colour, with large +oscula, which are not conspicuously raised above the surface but open +into very wide horizontal channels in the substance of the sponge. The +oscular collars are fairly well developed, but the subepidermal space is +not extensive. + +_Skeleton_ diffuse, consisting of very fine radiating fibres, which are +crossed at wide and irregular intervals by still finer transverse ones; +very little chitinoid substance present. + +_Spicules._ Skeleton-spicules smooth, slender, sharply pointed at both +ends, nearly straight. No true flesh-spicules. Gemmule-spicules straight +or nearly so, cylindrical, or constricted in the middle, obscurely +pointed or blunt, clothed with short, sharp, straight spines, which are +very numerous but not markedly longer at the two ends; these spicules +frequently found free in the parenchyma. + +_Gemmules_ numerous, small, free, spherical, yellow, with a +well-developed granular coat (in which the spicules are arranged almost +horizontally) and external to it a fine membrane which in preserved +specimens becomes puckered owing to unequal contraction; each gemmule +with a single aperture provided with a straight, rather wide, but very +delicate foraminal tubule. + + _Measurements of Spicules and Gemmules._ + + Length of skeleton-spicule 0.313 mm. + Breadth of skeleton-spicule 0.012 " + Length of gemmule-spicule 0.062 " + Breadth of gemmule-spicule 0.004 " + Diameter of gemmule 0.313-0.365 mm. + +This sponge in its general structure bears a very close resemblance to +_Spongilla crateriformis_. + +TYPE in the collection of the Indian Museum. + +HABITAT. Growing on weeds at the edge of the Sur Lake, Orissa, October +1908. Only one specimen was taken, together with many examples of _S. +lacustris_ subsp. _reticulata_, _S. carteri_ and _S. crassissima_. + + +7. Spongilla crateriformis* (_Potts_). + + _Meyenia crateriforma_, Potts, P. Ac. Philad. 1882, p. 12. + + _Meyenia crateriformis, id., ibid._ 1887, p. 228, pl. v, + fig. 6, pl. x, fig. 5. + + ? _Ephydatia crateriformis_, Hanitsch, Nature, ii, p. 511 + (1895). + + _Ephydatia crateriformis_, Weltner, Arch. Naturg. lxi (i), + pp. 122, 134 (1895). + + ? _Ephydatia crateriformis_, Hanitsch, Irish Natural. iv, p. + 125, pl. iv, fig. 5 (1895). + + _Ephydatia indica_, Annandale, J. Asiat. Soc. Bengal, 1907, + p. 20 (figures poor). + + _Ephydatia indica, id._, Rec. Ind. Mus. i, pp. 272, 279, + 388, 391 (1907). + + _Ephydatia crateriformis_, Scharff, European Animals, p. 34 + (1907). + + _Ephydatia crateriformis_, Annandale, P. U.S. Mus. xxxvii, + p. 402, fig. 1 (1909). + +_Sponge_ very fragile, forming soft irregular masses on the roots and +stems of water-plants, between which it is sometimes stretched as a +delicate film, or thin layers or cushions on flat surfaces. Oscula +large, flat, circular, or of irregular shape, opening into broad +horizontal canals, which at their distal end are superficial and often +covered by the external membrane only. Colour white, yellowish, greyish, +or blackish. + +_Skeleton_ very delicate; radiating fibres rarely consisting of more +than two parallel spicules; transverse fibres far apart, frequently +consisting of single spicules; very little spongin present. + +[Illustration: Fig 13.--Spicules of _Spongilla crateriformis_. + +A. From specimen taken in July in a tank on the Calcutta maidan. B. From +type specimen of _Ephydatia indica_ taken in the Indian Museum tank in +winter. Both figures x 240.] + +_Spicules._ Skeleton-spicules feebly curved, slender, as a rule +irregular in outline, sometimes almost smooth; the ends as a rule +sharply pointed, often constricted off and expanded so as to resemble +spear-heads, occasionally blunt. No true flesh-spicules. +Gemmule-spicules often free in the parenchyma, cylindrical, slender, +very variable in length in different sponges, straight or nearly so, as +a rule with an irregular circle of strong straight or recurved spines at +either end resembling a rudimentary rotule, and with shorter straight +spines scattered on the shaft, sometimes without the rudimentary rotule, +either truncate at the ends or terminating in a sharp spine. + +_Gemmules_ small, free, each surrounded by a thick granular layer in +which the spicules stand upright or nearly so, and covered externally by +a delicate but very distinct chitinous membrane; no horizontal spicules; +foramen situated at the base of a crater-like depression in the granular +coat, which is sometimes raised round it so as to form a conspicuous +rampart; a short, straight foraminal tubule. + +The shape of the spicules is extremely variable, and sponges in which +they are very different occur in the same localities and even in the +same ponds. It is possible that the differences are directly due to +slight changes in the environment, for in one pond in Calcutta a form +with _Spongilla_-like gemmule-spicules appears to replace the typical +form, which is common in winter, during the hot weather and "rains." I +have not, however, found this to be the case in other ponds. Perhaps _S. +hemephydatia_ will ultimately prove to be a variety of this very +variable species, but its smooth and regular skeleton-spicules and +short-spined gemmule-spicules afford a ready method of distinguishing it +from _S. crateriformis_. The two sponges are easily distinguished from +all others in the subgenus _Euspongilla_ by the upright and regular +arrangement of their gemmule-spicules, for although in _S. proliferens_ +and _S. travancorica_ some of the gemmule-spicules are nearly vertical, +their arrangement is always irregular, a large proportion of the +spicules make an acute angle with the inner coat of the gemmule and a +few as a rule lie parallel to it. The systematic position of _S. +crateriformis_ is almost exactly intermediate between _Euspongilla_ and +_Ephydatia_, to which genus it has hitherto been assigned. I think, +however, that taking into consideration its close relationship to _S. +hemephydatia_, it is best to assign it to _Spongilla_, as its +rudimentary rotules never form distinct disks. I have examined some of +Potts's original specimens from different American localities and can +detect no constant difference between them and Indian specimens. + +TYPES in the United States National Museum; co-types in Calcutta. + +GEOGRAPHICAL DISTRIBUTION.--This sponge was originally described from +North America (in which continent it is widely distributed) and has been +recorded from the west of Ireland with some doubt. In India and Burma it +is widely distributed. BENGAL, Calcutta and neighbourhood (_Annandale_); +Sonarpur, Gangetic delta (_Annandale_); BOMBAY PRESIDENCY, Igatpuri +Lake, W. Ghats (altitude _ca._ 2,000 feet) (_Annandale_); MADRAS +PRESIDENCY, neighbourhood of Madras town (_J. R. Henderson_); Museum +compound, Egmore (Madras town) (_Annandale_); near Bangalore (alt. _ca._ +3,000 ft.), Mysore State (Annandale); Ernakulam, Cochin (_G. Mathai_): +BURMA, Kawkareik, interior of Amherst district, Tenasserim, and the +Moulmein waterworks in the same district (_Annandale_).[AB] + + [Footnote AB: Mr. C. A. Paiva, Assistant in the Indian + Museum, has lately (March 31st, 1911) obtained specimens of + _S. crateriformis_ in a small pond of fresh water on Ross + Island in the Andaman group. The existence of this widely + distributed species on an oceanic island is noteworthy.] + +BIOLOGY.--_S. crateriformis_ flourishes in Calcutta throughout the year. +Here it is usually found adhering to the roots of water-plants, +especially _Pistia_ and _Limnanthemum_. In the case of the former it +occurs at the surface, in that of the latter at the bottom. When growing +near the surface or even if attached to a stone at the bottom in clear +water, it is invariably of a pale yellowish or greyish colour. When +growing on the roots of _Limnanthemum_ in the mud of the Gangetic +alluvium, however, it is almost black, and when growing in the reddish +muddy waters of the tanks round Bangalore of a reddish-brown colour. +This appears to be due entirely to the absorption of minute particles of +inorganic matter by the cells of the parenchyma. If black sponges of the +species are kept alive in clean water, they turn pure white in less than +a week, apparently because these particles are eliminated. When growing +on stones the sponge, as found in India, often conforms exactly with +Potts's description: "a filmy grey sponge, branching off here and there +... yet with a curious lack of continuity...." + +The wide efferent canals of this sponge afford a convenient shelter to +small crustacea, and the isopod _Tachaea spongillicola_, Stebbing (see p. +94), is found in them more abundantly than in those of any other sponge. +This is especially the case when the sponge is growing at the bottom. On +the surface of the sponge I have found a peculiar protozoon which +resembles the European _Trichodina spongillae_ in general structure but +belongs, I think, to a distinct species, if not to a distinct genus. + + +Subgenus B. EUNAPIUS, _J. E. Gray_. + + _Eunapius_, J. E. Gray (_partim_), P. Zool. Soc. London, + 1867, p. 552. + + _Spongilla_ (_s. str._), Vejdovsky, in Potts's "Fresh-Water + Sponges," P. Ac. Philad. 1887, p. 172. + + _Spongilla_ (_s. str._), Weltner, in Zacharias's Tier- und + Pflanzenwelt des Suesswassers, i, p. 214 (1891). + + _Spongilla_ (_s. str._), Annandale, Zool. Jahrb., Syst. + xxvii, p. 559 (1909). + +TYPE, _Spongilla carteri_, Carter. + +Spongillae in which the gemmules are covered with layers of distinct +polygonal air-spaces with chitinous walls. + +The gemmules are usually fastened together in groups, which may either +be free in the sponge or adhere to its support as a "pavement layer"; +sometimes, however, they are not arranged in this manner, but are quite +independent of one another. The skeleton is usually delicate, sometimes +very stout (_e. g._, in _S. nitens_, Carter). + +The term _Eunapius_ here used is not quite in the original sense, for +Gray included under it Bowerbank's _Spongilla paupercula_ which is now +regarded as a form of _S. lacustris_. His description, nevertheless, +fits the group of species here associated except in one particular, +viz., the smoothness of the gemmule-spicules to which he refers, for +this character, though a feature of _S. carteri_, is not found in +certain closely allied forms. The use of "_Spongilla_" in a double sense +may be avoided by the adoption of Gray's name. + +The subgenus _Eunapius_ is, like _Euspongilla_, cosmopolitan. It is not, +however, nearly so prolific in species. Four can be recognized in India, +two of which range, in slightly different forms, as far north as Europe, +one of them also being found in North America, Northern Asia, and +Australia. + + +8. Spongilla carteri* _Carter_ (_Bowerbank_, in litt.). (Plate II. fig. +1.) + + _Spongilla friabilis_?, Carter (_nec_ Lamarck), J. Bombay + Asiat. Soc. iii, p. 31, pl. i, fig. 3 (1849), & Ann. Nat. + Hist. (2) iv, p. 83, pl. ii. fig. 3 (1849). + + _Spongilla carteri_, Carter, Ann. Nat. Hist. (3) iii, p. + 334, pl. viii, figs. 1-7 (1859). + + _Spongilla carteri_, Bowerbank, P. Zool. Soc. London, 1863, + p. 469, pl. xxxviii, fig. 20. + + _Eunapius carteri_, J. E. Gray, _ibid._ 1867, p. 552. + + _Spongilla carteri_, Carter, Ann. Nat. Hist. (5) vii, p. 86 + (1881). + + _Spongilla carteri_, _id._, _ibid._ x, p. 369 (1882). + + _Spongilla carteri_, Potts, P. Ac. Philad. 1887, p. 194. + + _Spongilla carteri_, Weltner, Arch. Naturg. lxi (i), pp. + 117, 134 (1895). + + _Spongilla carteri_, Kirkpatrick, P. Zool. Soc. London, 1906 + (i), p. 219, pl. xv, figs. 3, 4 (? figs. 1, 2). + + _Spongilla carteri_, Annandale, J. Asiat. Soc. Bengal, 1906, + p. 188, pl. i, fig. 1. + + _Spongilla carteri_, Willey, Spolia Zeyl. iv, p. 184 (1907). + + _Spongilla carteri_, Annandale, _ibid._ vii, p. 63, pl. 1, + fig. 1 (1910). + +[Illustration: Fig. 14.--Gemmule of _Spongilla carteri_ (from Calcutta), +as seen in optical section, x 140.] + +_Sponge_ massive, as a rule with the surface smooth and rounded, +occasionally bearing irregular ridges, which may even take the form of +cockscombs; the oscula large, rounded, conspicuous but not raised above +the surface of the sponge, leading into broad vertical canals; the +lateral canals, except in the immediate vicinity of the central vertical +ones, not very broad; the oscular collars extending for a considerable +distance over the oscula in living or well-preserved specimens, never +standing out from the surface; the oscula never surrounded by radiating +furrows. The inhalent pores surrounded externally by unmodified cells of +the external membrane. Colour greyish, sometimes with a flush of green +on the external surface. + +The sponge has a peculiarly strong and offensive smell. + +_Skeleton_ fairly compact, with well-developed radiating fibres; the +transverse fibres splayed out at either end so that they sometimes +resemble a pair of fans joined together by the handles (fig. 3, p. 33). +A moderate amount of spongin present. + +_Spicules._ Skeleton-spicules smooth, pointed, nearly straight, never +very stout but somewhat variable in exact proportions. Gemmule-spicules +similar but much smaller. (There are no true flesh-spicules, but +immature skeleton-spicules may easily be mistaken for them.) + +_Gemmules_ as a rule numerous, spherical or flattened at the base, +variable in size, each covered by a thick coat consisting of several +layers of relatively large polygonal air-spaces. A single aperture +surrounded by a crater-like depression in the cellular coat and provided +with a foraminal tubule resembling an inverted bottle in shape. (This +tubule, which does not extend beyond the surface of the cellular coat, +is liable to be broken off in dried specimens.) The spicules variable in +quantity, arranged irregularly among the spaces of the cellular coat and +usually forming a sparse horizontal layer on its external surface. Each +gemmule contained in a cage of skeleton-spicules, by the pressure of +which it is frequently distorted. + + +8_a._ Var. mollis*, nov. + +This variety is characterized by a paucity of skeleton-spicules. The +sponge is therefore soft and so fragile that it usually breaks in pieces +if lifted from the water by means of its support. Owing to the paucity +of skeleton-spicules, which resemble those of the typical form +individually, the radiating and transverse fibres are extremely +delicate. + +Common in Calcutta. + + +8_b._ Var. cava*, nov. + +This variety is characterized by the fact that the oscula open into +broad horizontal canals, the roof of which is formed by a thin layer of +parenchyma and skeleton or, in places, of the external membrane only. +The skeleton is loose and fragile, and the living sponge has a peculiar +glassy appearance. In spirit the colour is yellowish, during life it is +greenish or white. + +Taken at Bombay; November, 1907. + + +8_c._ Var. lobosa*, nov. + +The greater part of the sponge in this variety consists of a number of +compressed but pointed vertical lobes, which arise from a relatively +shallow, rounded base, in which the oscula occur. The dried sponge has a +yellowish colour. + +Apparently common in Travancore. + + * * * * * + +I cannot distinguish these three "varieties"[AC] from the typical form +as distinct species; indeed, their status as varieties is a little +doubtful in two cases out of the three. Var. _cava_ appears to be a +variety in the strict sense of the word (see p. 18), for it was found on +the island of Bombay, the original locality of the species, growing side +by side with the typical form. Var. _lobosa_, however, should perhaps be +regarded as a subspecies rather than a variety, for I have received +specimens from two localities in the extreme south-west of India and +have no evidence that the typical form occurs in that part of the +country. Evidence, however, is rather scanty as regards the occurrence +of freshwater sponges in S. India. Var. _mollis_, again, may be a phase +directly due to environment. It is the common form in the ponds of +certain parts (_e. g._ in the neighbourhood of the Maidan and at +Alipore) of the Calcutta municipal area, but in ponds in other parts +(_e. g._ about Belgatchia) of the same area, only the typical form is +found. It is possible that the water in the former ponds may be +deficient in silica or may possess some other peculiarity that renders +the production of spicules difficult for _S. carteri_; but this seems +hardly probable, for _S. crassissima_, a species with a rather dense +siliceous skeleton, flourishes in the same ponds. I have noticed that in +ponds in which the aquatic vegetation is luxuriant and such genera of +plants as _Pistia_ and _Limnanthemum_ flourish, there is always a +tendency for _S. carteri_ to be softer than in ponds in which the +vegetation is mostly cryptogamic, and in Calcutta those parts of the +town in which sponges of this species produce most spicules are those in +which a slight infiltration of brackish water into the ponds may be +suspected; but in the interior of India, in places where the water is +absolutely fresh, hard specimens seem to be the rule rather than the +exception. + + [Footnote AC: The only complete European specimen of the + species I have seen differs considerably in outward form + from any Indian variety, consisting of a flat basal area + from which short, cylindrical turret-like branches arise. + This specimen is from Lake Balaton in Hungary and was sent + me by Prof. von Daday de Dees of Buda-Pesth.] + +_S. carteri_ is closely related to _S. nitens_, Carter (Africa, and +possibly S. America), but differs from that species in its comparatively +slender, sharp skeleton-spicules and smooth gemmule-spicules. It may +readily be distinguished from all other Indian freshwater sponges by its +large, deep, round oscula, but this feature is not so marked in var. +_lobosa_ as in the other forms. The typical form and var. _mollis_ grow +to a larger size than is recorded for any other species of the family. I +possess a specimen of the typical form from the neighbourhood of +Calcutta which measures 30 x 27 cm. in diameter and 19.5 cm. in depth, +and weighs (dry) 24-3/4 oz. The base of this specimen, which is solid +throughout, is nearly circular, and the general form is mound-shaped. +Another large specimen from Calcutta is in the form of an irregular +wreath, the greatest diameter of which is 34 cm. This specimen weighs +(dry) 16-1/4 oz. Both these specimens probably represent the growth of +several years. + +TYPES.--The types of the varieties _mollis_, _cava_ and _lobosa_ are in +the collection of the Indian Museum. I regard as the type of the species +the specimen sent by Carter to Bowerbank and by him named _S. carteri_, +although, owing to some confusion, Carter's description under this name +appeared some years before Bowerbank's. This specimen is in the British +Museum, with a fragment in the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--The range of the species extends westwards +to Hungary, southwards to Mauritius and eastwards to the island of +Madura in the Malay Archipelago; a specimen from Lake Victoria Nyanza in +Central Africa has been referred to it by Kirkpatrick (P. Zool. Soc. +London, 1906 (i), p. 219), but I doubt whether the identification is +correct. In India _S. carteri_ is by far the most universally +distributed and usually much the commonest freshwater sponge; it is one +of the only two species as yet found in Ceylon. Specimens are known from +the following localities:--PUNJAB, Lahore (_J. Stephenson_): BOMBAY +PRESIDENCY, island of Bombay (_Carter_, _Kirkpatrick_, _Annandale_); +Igatpuri, W. Ghats (alt. _ca._ 2,000 ft.) (_Annandale_): UNITED +PROVINCES (plains), Agra (_Kirkpatrick_); Lucknow: HIMALAYAS, Bhim Tal, +Kumaon (alt. 4,500 ft.) (_Annandale_); Tribeni, Nepal (_Hodgart_): +BENGAL, Calcutta and neighbourhood; Rajshahi (Rampur Bhulia) on the R. +Ganges about 150 miles N. of Calcutta (_Annandale_); Berhampur, +Murshidabad district (_R. E. Lloyd_); Pusa, Darbbhanga district +(_Bainbrigge Fletcher_); Siripur, Saran district, Tirhut (_M. +Mackenzie_); Puri and the Sur Lake, Orissa (_Annandale_): MADRAS +PRESIDENCY, near Madras town (_J. R. Henderson_); Madura district (_R. +Bruce Foote_); Bangalore (_Annandale_) and Worgaum, Mysore State +(2,500-3,000 ft.); Ernakulam and Trichur, Cochin (_G. Mathai_); +Trivandrum and the neighbourhood of C. Comorin, Travancore (var. +_lobosa_) (_R. S. N. Pillay_): BURMA, Kawkareik, interior of Amherst +district, Tenasserim (_Annandale_); Rangoon (_Annandale_); Bhamo, Upper +Burma (_J. Coggin Brown_): CEYLON, Peradeniya (_E. E. Green_); outlet of +the Maha Rambaikulam between Vavuniya and Mamadu, Northern Province +(_Willey_); Horowapotanana, between Trincomalee and Anuradihapura, +North-Central Province (_Willey_). + +BIOLOGY.--_S. carteri_ usually grows in ponds and lakes; I have never +seen it in running water. Mr. Mackenzie found it on the walls of old +indigo wells in Tirhut. + +The exact form of the sponge depends to some extent on the forces acting +on it during life. At Igatpuri, for instance, I found that specimens +attached to the stems of shrubs growing in the lake and constantly +swayed by the wind had their surface irregularly reticulated with high +undulating ridges, while those growing on stones at the bottom of a +neighbouring pond were smooth and rounded. + +Sponges of this species do not shun the light. + +In Calcutta _S. carteri_ flourishes during the cold weather (November to +March). By the end of March many specimens that have attached themselves +to delicate stems such as those of the leaves of _Limnanthemum_, or to +the roots of _Pistia stratiotes_, have grown too heavy for their support +and have sunk down into the mud at the bottom of the ponds, in which +they are quickly smothered. Others fixed to the end of branches +overhanging the water or to bricks at the edge have completely dried up. +A large proportion, however, still remain under water; but even these +begin to show signs of decay at this period. Their cells migrate to the +extremities of the sponge, leaving a mass of gemmules in the centre, and +finally perish. + +Few sponges exist in an active condition throughout the hot weather. The +majority of those that do so exhibit a curious phenomenon. Their surface +becomes smoothly rounded and they have a slightly pinkish colour; the +majority of the cells of their parenchyma, if viewed under a high power +of the microscope, can be seen to be gorged with very minute drops of +liquid. This liquid is colourless in its natural condition, but if the +sponge is plunged into alcohol the liquid turns of a dark brown colour +which stains both the alcohol and the sponge almost instantaneously. +Probably the liquid represents some kind of reserve food-material. Even +in the hot weather a few living sponges of the species may be found that +have not this peculiarity, but, in some ponds at any rate, the majority +that survive assume the peculiar summer form, which I have also found at +Lucknow. + +Reproduction takes place in _S. carteri_ in three distinct ways, two of +which may be regarded as normal, while the third is apparently the +result of accident. If a healthy sponge is torn into small pieces and +these pieces are kept in a bowl of water, little masses of cells +congregate at the tips of the radiating fibres of the skeleton and +assume a globular form. At first these cells are homogeneous, having +clear protoplasm full of minute globules of liquid. The masses differ +considerably in size but never exceed a few millimetres in diameter. In +about two days differentiation commences among the cells; then spicules +are secreted, a central cavity and an external membrane formed, and an +aperture, the first osculum, appears in the membrane. In about ten days +a complete young sponge is produced, but the details of development have +not been worked out. + +The most common normal form of reproduction is by means of gemmules, +which are produced in great numbers towards the end of the cold weather. +If small sponges are kept alive in an aquarium even at the beginning of +the cold weather, they begin to produce gemmules almost immediately, but +these gemmules although otherwise perfect, possess few or no +gemmule-spicules. If the sponge becomes desiccated at the end of the +cold weather and is protected in a sheltered place, some or all of the +gemmules contained in the meshes of its skeleton germinate _in situ_ as +soon as the water reaches it again during the "rains." It is by a +continuous or rather periodical growth of this kind, reassumed season +after season, that large masses of sponge are formed. In such masses it +is often possible to distinguish the growth of the several years, but as +a rule the layers become more or less intimately fused together, for no +limiting membrane separates them. A large proportion of the gemmules +are, however, set free and either float on the surface of the water that +remains in the ponds or are dried up and carried about by the wind. In +these circumstances they do not germinate until the succeeding cold +weather, even if circumstances other than temperature are favourable; +but as soon as the cold weather commences they begin to produce new +sponges with great energy. + +Sexual reproduction, the second normal form, takes place in _S. carteri_ +mainly if not only at the approach of a change of season, that is to say +about March, just before the hot weather commences, and about November, +just as the average temperature begins to sink to a temperate level. At +these seasons healthy sponges may often be found full of eggs and +embryos, which lie in the natural cavities of the sponge without +protecting membrane. + +In the ponds of Calcutta a large number of animals are found associated +in a more or less definite manner with _Spongilla carteri_. Only one, +however, can be described with any degree of certainty as being in +normal circumstances an enemy, namely the larva of _Sisyra indica_,[AD] +and even in the case of this little insect it is doubtful how far its +attacks are actually injurious to the sponge. The larva is often found +in considerable numbers clinging to the oscula and wide efferent canals +of _S. carteri_, its proboscis inserted into the substance of the +sponge. If the sponge dies and the water becomes foul the larvae swim or +crawl away. If the sponge dries up, they leave its interior (in which, +however, they sometimes remain for some days after it has become dry) +and pupate in a silken cocoon on its surface. Hence they emerge as +perfect insects after about a week. + + [Footnote AD: Needham. Rec. Ind. Mus. iii, p. 206 (1909).] + +An animal that may be an enemy of _S. carteri_ is a flat-worm (an +undescribed species of _Planaria_) common in its larger canals and +remarkable for the small size of its pharynx. The same worm, however, is +also found at the base of the leaves of bulrushes and in other like +situations, and there is no evidence that it actually feeds on the +sponge. Injured sponges are eaten by the prawn _Palaemon lamarrei_, +which, however, only attacks them when the dermal membrane is broken. A +_Tanypus_ larva (Chironomid Diptera) that makes its way though the +substance of the sponge may also be an enemy; it is commoner in decaying +than in vigorous sponges. + +The presence of another Chironomid larva (_Chironomus_, sp.) appears to +be actually beneficial. In many cases it is clear that this larva and +the sponge grow up together, and the larva is commoner in vigorous than +in decayed sponges. Unlike the _Tanypus_ larva, it builds parchment-like +tubes, in which it lives, on the surface of the sponge. The sponge, +however, often grows very rapidly and the larva is soon in danger of +being engulfed in its substance. The tube is therefore lengthened in a +vertical direction to prevent this catastrophe and to maintain +communication with the exterior. The process may continue until it is +over an inch in length, the older part becoming closed up owing to the +pressure of the growing sponge that surrounds it. Should the sponge die, +the larva lives on in its tubes without suffering, and the ends of tubes +containing larvae may sometimes be found projecting from the worn surface +of dead sponges. The larva does not eat the sponge but captures small +insects by means of a pair of legs on the first segment of its thorax. +In so doing it thrusts the anterior part of its body out of the tube, to +the inner surface of which it adheres by means of the pair of false legs +at the tip of the abdomen. This insect, which is usually found in the +variety _mollis_, appears to do good to the sponge in two ways--by +capturing other insects that might injure it and by giving support to +its very feeble skeleton. + +A precisely similar function, so far as the support of the sponge is +concerned, is fulfilled by the tubular zooecia of a phase of the +polyzoon _Plumatella fruticosa_ (see p. 218) which in India is more +commonly found embedded in the substance of _S. carteri_ than in that of +any other species, although in Great Britain it is generally found in +that of _S. lacustris_, which is there the commonest species of +freshwater sponge. + +Another animal that appears to play an active part in the oeconomy of +the sponge is a peculiar little worm (_Chaetogaster spongillae_) also +found among the zooecia of _Plumatella_ and belonging to a widely +distributed genus of which several species are found in association with +pond-snails. _Chaetogaster spongillae_ often occurs in enormous numbers in +dead or dying sponges of _S. carteri_, apparently feeding on the +decaying organic matter of the sponge and assisting by its movements in +releasing numerous gemmules. In so doing it undoubtedly assists in the +dissemination of the species. + +Major J. Stephenson (Rec. Ind. Mus. v, p. 233) has recently found two +other species of oligochaetes inhabiting _S. carteri_ var. _lobosa_ from +Travancore. Both these species, unlike _Chaetogaster spongillae_, belong +to a genus that is vegetarian in habits. One of them, _Nais pectinata_, +has not yet been found elsewhere, while the other, _Nais communis_, has +a very wide distribution. The latter, however, occurs in the sponge in +two forms--one with eyes, the other totally blind. The blind form (_N. +communis_ var. _caeca_) has only been found in this situation, but the +other (var. _punjabensis_) lives free as well as in association with the +sponge, in which the blind form was the commoner of the two. + +The majority of the animals found in association with _S. carteri_ gain +shelter without evident assistance to the sponge. This is the case as +regards the little fish (_Gobius alcockii_), one of the smallest of the +vertebrates (length about 1/2 inch), which lays its eggs in the patent +oscula, thus securing for them a situation peculiarly favourable to +their development owing to the constant current of water that passes +over them. In the absence of sponges, however, this fish attaches its +eggs to the floating roots of the water-plant _Pistia stratiotes_. +Numerous small crustacea[AE] also take temporary or permanent refuge in +the cavities of _S. carteri_, the most noteworthy among them being the +Isopod _Tachaea spongillicola_[AF], the adults of which are found in the +canal of this and other sponges, while the young cling to the external +surface of the carapace of _Palaemon lamarrei_ and other small prawns. +Many worms and insects of different kinds also enter the canals of _S. +carteri_, especially when the sponge is becoming desiccated; from +half-dry sponges numerous beetles and flies may be bred, notably the +moth-fly _Psychoda nigripennis_[AG] of which enormous numbers sometimes +hatch out from such sponges. + + [Footnote AE: According to the late Rai Bahadur R. B. + Sanyal, freshwater sponges are called in Bengali "shrimps' + nests." From his description it is evident that he refers + mainly to _S. carteri_ (see Hours with Nature, p. 46; + Calcutta 1896).] + + [Footnote AF: Stebbing, J. Linn. Soc. xxx, p. 40; Annandale, + Rec. Ind. Mus. i, p. 279.] + + [Footnote AG: Brunetti, Rec. Ind. Mus. ii, p. 376 (1908).] + +As the sponge grows it frequently attaches itself to small molluscs such +as the young of _Vivipara bengalensis_, which finally become buried in +its substance and thus perish. Possibly their decaying bodies may afford +it nourishment, but of the natural food of sponges we know little. _S. +carteri_ flourishes best and reaches its largest size in ponds used for +domestic purposes by natives of India, and thrives in water thick with +soap-suds. It is possible, though direct proof is lacking, that the +sponge does good in purifying water used for washing the clothes, +utensils, and persons of those who drink the same water, by absorbing +decaying animal and vegetable matter from it. + +Various minute algae are found associated with _S. carteri_, but of these +little is yet known. The green flush sometimes seen on the surface of +the typical form is due to the fact that the superficial cells of the +parenchyma contain green corpuscles. These, however, are never very +numerous and are not found in the inner parts of the sponge, perhaps +owing to its massive form. It is noteworthy that these green bodies +flourish in large numbers throughout the substance of sponges of _S. +proliferens_, a species always far from massive, growing in the same +ponds as _S. carteri_. + + +9. Spongilla fragilis, _Leidy_. + + _Spongilla fragilis_, Leidy, P. Ac. Philad. 1851, p. 278. + + _Spongilla lordii_, Bowerbank, P. Zool. Soc. London, 1863, + p. 466, pl. xxxviii, fig. 17. + + _Spongilla contecta_, Noll, Zool. Garten*, 1870, p. 173. + + _Spongilla ottavaensis_, Dawson, Canad. Nat.* (new series) + viii, p. 5 (1878). + + _Spongilla sibirica_, Dybowski, Zool. Anz., Jahr. i, p. 53 + (1878). + + _Spongilla morgiana_, Potts, P. Ac. Philad. 1880, p. 330. + + _Spongilla lordii_, Carter, Ann. Nat. Hist. (5) vii, p. 89, + pl. vi, fig. 13 (1881). + + _Spongilla sibirica_, Dybowski, Mem. Ac. St. Petersb. (7) + xxx, no. x, p. 10, fig. 12. + + _Spongilla glomerata_, Noll, Zool. Anz., Jahr. ix, p. 682 + (1886). + + _Spongilla fragilis_, Vejdovsky, P. Ac. Philad. 1887, p. + 176. + + _Spongilla fragilis_, Potts, _ibid._ p. 197, pl. v, fig. 2; + pl. viii, figs. 1-4. + + _Spongilla fragilis_, Weltner, Arch. Naturg. lix (1), p. + 266, pl. ix, figs. 18-20 (1893). + + _Spongilla fragilis_, _id._, Arch. Naturg. lxi (i), p. 117 + (1895). + + _Spongilla fragilis_, _id._, in Semon's Zool. Forsch. in + Austral. u. d. Malay. Arch. v, part v, p. 523. + + _Spongilla fragilis_, Annandale, P. U.S. Mus. xxxvii, p. 402 + (1909). + + _Spongilla fragilis_, _id._, Annot. Zool. Japon. vii, part + ii, p. 106, pl. ii, fig. 1 (1909). + +_Sponge_ flat, lichenoid, never of great thickness, devoid of branches, +dense in texture but very friable; colour brown, green, or whitish; +oscula numerous, small, flat, distinctly star-shaped. + +_Skeleton_ with well defined radiating and transverse fibres, which are +never strong but form a fairly dense network with a small amount of +spongin. + +_Spicules._ Skeleton-spicules smooth, sharply pointed, moderately stout, +as a rule nearly straight. No flesh-spicules. Gemmule-spicules +cylindrical, blunt or abruptly pointed, nearly straight, covered with +relatively stout, straight, irregular spines, which are equally +distributed all over the spicule. + +_Gemmules_ bound together in free groups of varying numbers and forming +a flat layer at the base of the sponge; each gemmule small in size, +surrounded by a thick cellular coat of several layers; with a relatively +long and stout foraminal tubule, which projects outwards through the +cellular coat at the sides of the group or at the top of the basal layer +of gemmules, is usually curved, and is not thickened at the tip; more +than one foraminal tubule sometimes present on a single gemmule; +gemmule-spicules arranged horizontally or at the base of the cellular +coat. + +The species as a species is easily distinguished from all others, its +nearest ally being the N. American _S. ingloriformis_ with sparsely +spined skeleton-spicules which are very few in number, and gemmule +groups in which the foraminal tubules all open downwards. + +Several varieties of _S. fragilis_ have been described in Europe and +America. + +TYPE.--Potts refers to the type as being in the Academy of Natural +Sciences at Philadelphia. + +GEOGRAPHICAL DISTRIBUTION.--All over Europe and N. America; also in +Siberia, Australia, and S. America. The species is included in this work +in order that its Asiatic local races may be fitly described. + + +9 _a._ Subsp. calcuttana*, nov. + + ? _Spongilla decipiens_, Weltner (_partim_), Arch. Naturg. + lxi (i), pp. 117, 134 (1895). + + _Spongilla decipiens_, Annandale, Journ. As. Soc. Beng. + 1906, p. 57. + + _Spongilla fragilis_, _id._, Rec. Ind. Mus. i, p. 390 + (1907). + +[Illustration: Fig. 15.--_Spongilla fragilis_ subsp. _calcuttana_. +A=group of gemmules, x 70; B=spicules, x 240. From type specimen.] + +This local race, which is common in Calcutta, is distinguished from the +typical form mainly by the shape of its skeleton-spicules, most of which +are abruptly pointed or almost rounded at the tips, sometimes bearing a +minute conical projection at each end. The gemmule-spicules, which are +usually numerous, are slender. The foraminal tubules are usually long +and bent, but are sometimes very short and quite straight. The colour is +usually greyish, occasionally brown. + +I have not found this race except in Calcutta, in the ponds of which it +grows on bricks or, very commonly, on the stems of bulrushes, often +covering a considerable area. + +TYPE in the Indian Museum. + + +9 _b._ Subsp. decipiens*, _Weber_. + + _Spongilla decipiens_, Weber, Zool. Ergeb. Niederlaend. + Ost-Ind. i, p. 40, pl. iv, figs. 1-5 (1890). + +This (?) local race is distinguished by the fact that the foraminal +tubules are invariably short and straight and thickened at the tips, and +that gemmule-spicules do not occur on the external surface of the +cellular coat of the gemmules. + +I include Weber's _Spongilla decipiens_ in the Indian fauna on the +authority of Weltner, who identified specimens from the Museum "tank," +Calcutta, as belonging to this form. All, however, that I have examined +from our "tank" belong to the subspecies _calcuttana_, most of the +skeleton-spicules of which are much less sharp than those of +_decipiens_. By the kindness of Prof. Max Weber I have been able to +examine a co-type of his species, which is probably a local race +peculiar to the Malay Archipelago. + +TYPE in the Amsterdam Museum; a co-type in Calcutta. + +Perhaps the Japanese form, which has spindle-shaped gemmule-spicules +with comparatively short and regular spines, should be regarded as a +third subspecies, and the Siberian form as a fourth. + + +10. Spongilla gemina*, sp. nov. + +_Sponge_ forming small, shallow, slightly dome-shaped patches of a more +or less circular or oval outline, minutely hispid on the surface, +friable but moderately hard. Oscula numerous but minute and +inconspicuous, never star-shaped. Dermal membrane adhering closely to +the sponge. Colour grey or brown. + +_Skeleton_ forming a close and regular network at the base of the +sponge, becoming rather more diffuse towards the external surface; the +radiating and the transverse fibres both well developed, of almost equal +diameter. Little spongin present. + +_Spicules._ Skeleton-spicules slender, smooth, sharply pointed. No +flesh-spicules. Gemmule-spicules long, slender, cylindrical, blunt or +bluntly pointed, somewhat irregularly covered with minute straight +spines. + +_Gemmules_ small, bound together in pairs, as a rule free in the +parenchyma but sometimes lightly attached at the base of the sponge. +Each gemmule flattened on the surface by which it is attached to its +twin, covered with a thin coat of polygonal air-spaces which contains +two layers of gemmule-spicules crossing one another irregularly in a +horizontal plane. One or two foraminal tubules present on the surface +opposite the flat one, bending towards the latter, often of considerable +length, cylindrical and moderately stout. + +TYPE in the Indian Museum. + +This species is closely allied to _S. fragilis_, from which it may be +distinguished by the curious twinned arrangement of its gemmules. It +also differs from _S. fragilis_ in having extremely small and +inconspicuous oscula. + +_Locality._ I only know this sponge from the neighbourhood of Bangalore, +where Dr. Morris Travers and I found it in October, 1910 growing on +stones and on the leaves of branches that dipped into the water at the +edge of a large tank. + + +11. Spongilla crassissima*, _Annandale_. + + _Spongilla crassissima_, Annandale, J. Asiat. Soc. Bengal, + 1907, p. 17, figs. 2, 3. + + _Spongilla crassissima_, _id._, _ibid._ p. 88. + + _Spongilla crassissima_, _id._, Rec. Ind. Mus. i. p. 390, + pl. xiv, fig. 4 (1907). + +_Sponge_ very hard and strong, nearly black in colour, sometimes with a +greenish tinge, forming spherical, spindle-shaped or irregular masses +without branches but often several inches in diameter. Oscula circular +or star-shaped, usually surrounded by radiating furrows; pores normally +contained in single cells. External membrane closely adherent to the +sponge except immediately round the oscula. + +_Skeleton_ dense, compact and only to be broken by the exercise of +considerable force; radiating and transverse fibres not very stout but +firmly bound together by spongin (fig. 6, p. 38), which occasionally +extends between them as a delicate film; their network close and almost +regular. + +_Spicules._ Skeleton-spicules smooth, feebly curved, sausage-shaped but +by no means short, as a rule bearing at each end a minute conical +projection which contains the extremity of the axial filament. No +flesh-spicules. Gemmule-spicules closely resembling those of _S. +fragilis_ subsp. _calcuttana_, but as a rule even more obtuse at the +ends. + +_Gemmules_ as in _S. fragilis_ subsp. _calcuttana_; a basal layer of +gemmules rarely formed. + + +11 _a._ Var. crassior*, _Annandale_. + + _Spongilla crassior_, Annandale, Rec. Ind. Mus. i, p. 389, + pl. xiv, fig. 3 (1907). + +This variety differs from the typical form chiefly in its even stronger +skeleton (fig. 3, p. 33) and its stouter skeleton-spicules, which do not +so often possess a terminal projection. The sponge is of a brownish +colour and forms flat masses of little thickness but of considerable +area on sticks and on the stems of water-plants. + +TYPES.--The types of both forms are in the Indian Museum. Co-types have +been sent to London. + +GEOGRAPHICAL DISTRIBUTION.--This sponge is only known from Bengal. The +variety _crassior_ was found at Rajshahi (Rampur Bhulia) on the Ganges, +about 150 miles N. of Calcutta, while the typical form is fairly common +in the "tanks" of Calcutta and very abundant in the Sur Lake near Puri +in Orissa. + +[Illustration: Fig. 16.--Spicules of _Spongilla crassissima_ var. +_crassior_ (from type specimen), x 240.] + +BIOLOGY.--_S. crassissima_ is usually found near the surface in shallow +water. Attached to the roots of the floating water-plant _Pistia +stratiotes_ it assumes a spherical form, while on sticks or like objects +it is spindle-shaped. Sometimes it is found growing on the same stick or +reed-stem as _S. carteri_, the two species being in close contact and +_S. carteri_ always overlapping _S. crassissima_. The dark colour is due +to minute masses of blackish pigment in the cells of the parenchyma. The +dense structure of the sponge is not favourable to the presence of +_incolae_, but young colonies of the polyzoon _Plumatella fruticosa_ are +sometimes overgrown by it. Although they may persist for a time by +elongating their tubular zooecia through the substance of the sponge, +they do not in these circumstances reach the same development as when +they are overgrown by the much softer _S. carteri_. + +_S. crassissima_ is found during the "rains" and the cold weather. In +Calcutta it attains its maximum size towards the end of the latter +season. In spite of its hard and compact skeleton, the sponge does not +persist from one cold weather to another. + +A curious phenomenon has been noticed in this species, but only in the +case of sponges living in an aquarium, viz. the cessation during the +heat of the day of the currents produced by its flagella. + + +Subgenus C. STRATOSPONGILLA, _Annandale_. + + _Stratospongilla_, Annandale, Zool. Jahrb., Syst. xxvii, p. + 561 (1909). + +TYPE, _Spongilla bombayensis_, Carter. + +Spongillae in the gemmules of which the pneumatic layer is absent or +irregularly developed, its place being sometimes taken by air-spaces +between the stout chitinous membranes that cover the gemmule. At least +one of these membranes is always present. + +The gemmule-spicules lie in the membrane or membranes parallel to the +surface of the gemmule, and are often so arranged as to resemble a +mosaic. The gemmules themselves are usually adherent to the support of +the sponge. The chitinous membrane or membranes are often in continuity +with a membrane that underlies the base of the sponge. The skeleton is +usually stout, though often almost amorphous, and the skeleton-spicules +are sometimes sausage-shaped. + +Sponges of this subgenus form crusts or sheets on solid submerged +objects. + +_Stratospongilla_ is essentially a tropical subgenus, having its +head-quarters in Central Africa and Western India. One of its species, +however, (_S. sumatrana_*, Weber) occurs both in Africa and the Malay +Archipelago, while another has only been found in S. America (_S. +navicella_, Carter). + +Aberrant species occur in China (_S. sinensis_*, _S. coggini_*) and the +Philippines (_S. clementis_*). Three species have been found in the +Bombay Presidency and Travancore, one of which (_S. bombayensis_*) +extends its range eastwards to Mysore and westwards across the Indian +Ocean to Natal. + + +12. Spongilla indica*, _Annandale_. + + _Spongilla indica_, Annandale, Rec. Ind. Mus. ii, p. 25, + figs. 1, 2 (1908). + +_Sponge_ forming a very thin layer, of a bright green or pale grey +colour; surface smooth, minutely hispid; pores and oscula inconspicuous, +the latter approached in some instances by radiating furrows; subdermal +cavity small; texture compact, rather hard. + +_Skeleton_ incoherent, somewhat massive owing to the large number of +spicules present. Spicules forming triangular meshes and occasionally +arranged in vertical lines several spicules broad but without spongin. + +_Spicules._ Skeleton-spicules straight or nearly straight, slender, +cylindrical, amphistrongylous, uniformly covered with minute, sharp +spines; flesh-spicules slender, sharply pointed, straight or curved, +irregularly covered with relatively long, straight sharp spines, +abundant in the dermal membrane, scarce in the substance of the sponge. +Gemmule-spicules short, stout, sausage-shaped, covered with minute +spines, which are sometimes absent from the extremities. + +_Gemmules_ spherical, somewhat variable in size, with a single aperture, +which is provided with a trumpet-shaped foraminal tubule and is situated +at one side of the gemmule in its natural position; the inner chitinous +coat devoid of spicules, closely covered by an outer coat composed of a +darkly coloured chitinoid substance in which the gemmule-spicules are +embedded, lying parallel or almost parallel to the inner coat. The outer +coat forms a kind of mantle by means of the skirts of which the gemmule +is fastened to the support of the sponge. This coat is pierced by the +foraminal tubule. The gemmules are distinct from one another. + +[Illustration: Fig. 17.--Gemmule of _Spongilla indica_ seen from the +side (from type specimen), magnified.] + + Average length of skeleton-spicules 0.2046 mm. + " breadth of skeleton-spicules 0.0172 " + " length of flesh-spicules 0.053 " + " breadth of flesh-spicules 0.0053 " + " length of gemmule-spicules 0.044 " + " breadth of gemmule-spicules 0.0079 " + +_S. indica_ is closely allied to _S. sumatrana_*, Weber, which has been +found both in the Malay Archipelago and in East Africa. It may be +distinguished by its blunt, almost truncated megascleres and +comparatively slender gemmule-spicules. + +TYPE in the Indian Museum. + +HABITAT, etc.--Growing, together with _S. cinerea_ and _Corvospongilla +lapidosa_, on the stone sides of an artificial conduit in the R. +Godaveri at Nasik on the eastern side of the Western Ghats in the Bombay +Presidency. The water was extremely dirty and was used for bathing +purposes. The sponge was green where the light fell upon it, grey where +it was in the shadow of the bridge under which the conduit ran. The only +specimens I have seen were taken in November, 1907. + + +13. Spongilla bombayensis*, _Carter_. (Plate II, fig. 2.) + + _Spongilla bombayensis_, Carter, Ann. Nat. Hist. (5) x, p. + 369, pl. xvi, figs. 1-6 (1882). + + _Spongilla bombayensis_, Annandale, Zool. Jahrb., Syst. + xxvii, p. 562, figs. B, C (1909). + +_Sponge_ hard but friable, forming thin layers or cushions; its surface +often irregular but without a trace of branches; its area never very +great; oscula inconspicuous; external membrane adhering closely to the +sponge; colour brownish or greyish. + +[Illustration: Fig. 18.--Gemmule of _Spongilla bombayensis_ as seen from +above (from type specimen), magnified.] + +_Skeleton_ almost amorphous, very dense, consisting of large numbers of +spicules arranged irregularly; radiating fibres occasionally visible in +sections, but almost devoid of spongin; a more or less definite +reticulation of horizontal spicules lying immediately under the external +membrane. + +_Spicules._ Skeleton-spicules slender, pointed, feebly curved, +irregularly roughened or minutely spined all over the surface. +Flesh-spicules straight, narrowly rhomboidal in outline, sharply +pointed, slender, covered with minute, irregular, straight spines, +scanty in the parenchyma, abundant in the external membrane. +Gemmule-spicules sausage-shaped or bluntly pointed, variable in length +but usually rather stout, covered with minute spines, as a rule +distinctly curved. + +_Gemmules_ round or oval, firmly adherent[AH] to the base of the sponge, +as a rule rather shallowly dome-shaped, covered by two thick chitinous +membranes, in each of which there is a dense horizontal layer of +spicules; no granular or cellular covering; the two chitinous coats +separated by an empty space; the aperture or apertures on the side of +the gemmule in its natural position, provided with foraminal tubules, +which may be either straight or curved, project through the outer +chitinous membrane and often bend down towards the base of the gemmule. +The spicules of the outer layer often more irregular in outline and less +blunt than those of the inner layer. + + [Footnote AH: The outer covering by means of which the + gemmule is fixed is not formed until the other structures + are complete. In young sponges, therefore, free gemmules may + often be found.] + +This sponge is allied to _S. indica_, but is distinguished among other +characters by its sharp skeleton-spicules and by the fact that the +gemmule is covered by two chitinous membranes instead of one. + +TYPE in the British Museum; a fragment in the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--S. and W. India and S. Africa. Carter's type +was found in the island of Bombay, my own specimens in Igatpuri Lake in +the Western Ghats. I have recently (October 1910) found sponges and bare +gemmules attached to stones at the end of a tank about 10 miles from +Bangalore (Mysore State) in the centre of the Madras Presidency. Prof. +Max Weber obtained specimens in Natal. + +BIOLOGY.--The specimens collected by Prof. Weber in Natal and those +collected by myself in the Bombay Presidency were both obtained in the +month of November. It is therefore very interesting to compare them from +a biological point of view. In so doing, it must be remembered that +while in S. Africa November is near the beginning of summer, in India it +is at the beginning of the "cold weather," that is to say, both the +coolest and the driest season of the year. The lake in which my +specimens were obtained had, at the time when they were collected, +already sunk some inches below its highest level, leaving bare a gently +sloping bank of small stones. Adhering to the lower surface of these +stones I found many small patches of _Spongilla bombayensis_, quite dry +but complete so far as their harder parts were concerned and with the +gemmules fully formed at their base. From the shallow water at the edge +of the lake I took many similar stones which still remained submerged. +It was evident that the sponge had been just as abundant on their lower +surface as on that of the stones which were now dry; but only the +gemmules remained, sometimes with a few skeleton-spicules adhering to +them (Pl. II, fig. 2). The bulk of the skeleton had fallen away and the +parenchyma had wholly perished. In a few instances a small sponge, one +or two millimetres in diameter, had already been formed among the +gemmules; but these young sponges appeared to belong to some other +species, possibly _Spongilla indica_, which was also common in the lake. + +Carter's specimen of _S. bombayensis_, which was evidently in much the +same condition as those I found still submerged a month later, was taken +in October in a disused quarry. It was surrounded by a mass of _S. +carteri_ three inches in diameter, and was attached to a herbaceous +annual. The point on the edge of the quarry at which this plant grew was +not reached by the water until July. It is therefore necessary to assume +that the gemmules of _S. bombayensis_ had been formed between July and +October. Probably the larva of the sponge had settled down on the plant +during the "rains"--which commence in Bombay about the beginning of +June--and had grown rapidly. The production of gemmules may have been +brought about owing to the sponge being choked by the more vigorous +growth of _S. carteri_, a species which grows to a considerable size in +a comparatively short time, while _S. bombayensis_ apparently never +reaches a thickness of more than a few millimetres. + +The manner in which the gemmules of _S. bombayensis_ are fastened to the +solid support of the sponge must be particularly useful in enabling them +to sprout in a convenient environment as soon as the water reaches them. +The fact that the gemmules remained fixed without support renders it +unnecessary for the skeleton to persist as a cage containing them (or at +any rate a proportion of them) during the period of rest. + +Prof. Weber's specimens of _S. bombayensis_ were collected in a river, +apparently on stones or rocks, towards the beginning of the S. African +summer. They contain comparatively few gemmules and were evidently in a +vigorous condition as regards vegetative growth. Unfortunately we know +nothing of the seasonal changes which take place in freshwater sponges +in S. Africa, but the difference between these changes in Europe and in +India shows that they are dependent on environment as well as the +idiosyncrasy of the species. It is very interesting, therefore, to see +that the condition of sponges taken in S. Africa differs so widely from +that of other individuals of the same species taken in India at the same +season. + +In Prof. Weber's specimens I have found numerous small tubules of +inorganic debris. These appear to be the work of Chironomid larvae, of +which there are several specimens loose in the bottle containing the +sponges. Other tubules of a very similar appearance but with a delicate +chitinoid foundation appear to be the remains of a species of +_Plumatella_ of which they occasionally contain a statoblast. + + +14. Spongilla ultima*, _Annandale_. (Plate II, fig. 3.) + + _Spongilla ultima_, Annandale, Rec. Ind. Mus. v, p. 31 (1910). + +_Sponge_ hard and strong, forming a thin layer on solid objects, of a +pale green colour (dry); the oscula small but rendered conspicuous by +the deep radiating furrows that surround them; external surface of the +sponge rough but not spiny. + +_Skeleton_ forming a compact but somewhat irregular reticulation in +which the radiating fibres are not very much more distinct than the +transverse ones; a considerable amount of almost colourless spongin +present. + +_Spicules._ Skeleton-spicules smooth, stout, amphioxous, as a rule +straight or nearly straight, not infrequently inflated in the middle or +otherwise irregular. No flesh-spicules. Gemmule-spicules variable in +size, belonging to practically every type and exhibiting practically +every abnormality possible in the genus, the majority being more or less +sausage-shaped and having a roughened surface, but others being +cruciform, spherical, subspherical, rosette-like, needle-like, bifid or +even trifid at one extremity. + +[Illustration: Fig. 19.--Spicules of _Spongilla ultima_ (from type +specimen), x 120.] + +_Gemmules_ adherent, spherical, large, each covered by two distinct +layers of horizontal spicules; the outer layer intermixed with +skeleton-spicules and often containing relatively large siliceous +spheres, a large proportion of the spicules being irregular in shape; +the spicules of the inner layer much more regular and as a rule +sausage-shaped. The outer layer is contained in a chitinous membrane +which spreads out over the base of the sponge. The foraminal tubules are +short and straight. + +This sponge is allied to _S. bombayensis_, from which it is +distinguished not only by the abnormal characters of its +gemmule-spicules and the absence of flesh-spicules, but also by the form +of its skeleton-spicules and the structure of its skeleton. I have +examined several specimens dry and in spirit; but _S. ultima_ is the +only Indian freshwater sponge, except _Corvospongilla burmanica_, I have +not seen in a fresh condition. + +TYPES in the Indian Museum; co-types at Trivandrum. + +HABITAT. Discovered by Mr. R. Shunkara Narayana Pillay, of the +Trivandrum Museum, in a tank near Cape Comorin, the southernmost point +of the Indian Peninsula. + + +Genus 2. PECTISPONGILLA, _Annandale_. + + _Pectispongilla_, Annandale, Rec. Ind. Mus. iii, p. 103 (1909). + +TYPE, _Pectispongilla aurea_, Annandale. + +The structure of the sponge resembling that of _Euspongilla_ or +_Ephydatia_; but the gemmule-spicules bear at either end, at one side +only, a double vertical row of spines, so that they appear when viewed +in profile like a couple of combs joined together by a smooth bar. + +[Illustration: Fig. 20.--Gemmule and spicules of _Pectispongilla aurea_ +(type specimen). _a_, Skeleton-spicules; _b_, gemmule-spicules; _b'_, a +single gemmule-spicule more highly magnified.] + +GEOGRAPHICAL DISTRIBUTION.--The genus is monotypic and is only known +from Travancore and Cochin in the south-west of the Indian Peninsula. + + +15. Pectispongilla aurea*, _Annandale_. + + _Pectispongilla aurea_, Annandale, _op. cit._, p. 103, pl. + xii, fig. 2. + +_Sponge_ forming minute, soft, cushion-like masses of a deep golden +colour (dull yellow in spirit); the surface smooth, minutely hispid. One +relatively large depressed osculum usually present in each sponge; pores +inconspicuous; dermal membrane in close contact with the parenchyma. + +_Skeleton_ consisting of slender and feebly coherent radiating fibres as +a rule two or three spicules thick, with single spicules or ill-defined +transverse fibres running horizontally. Towards the external surface +transverse spicules are numerous, but they do not form any very regular +structure. + +_Spicules._ Skeleton-spicules smooth, sharply pointed, straight or +nearly so. Gemmule-spicules minute, with the stem smooth and +cylindrical, relatively stout and much longer than the comb at either +end; the two combs equal, with a number of minute, irregularly scattered +spines between the two outer rows of stouter ones. No free microscleres. + +_Gemmules_ minute, spherical, with a single aperture, which is provided +with a very short foraminal tubule; the granular coat well developed; +the spicules arranged in a slanting position, but more nearly vertically +than horizontally, with the combs pointing in all directions; no +external chitinous membrane. + + Length of skeleton-spicule 0.2859 mm. + Greatest diameter of skeleton-spicule 0.014 " + Length of gemmule-spicule 0.032-0.036 mm. + Length of comb of gemmule-spicule 0.008 mm. + Greatest diameter of shaft of gemmule-spicule 0.004 " + Diameter of gemmule 0.204-0.221 mm. + +The gemmule-spicules first appear as minute, smooth, needle-like bodies, +which later become roughened on one side at either end and so finally +assume the mature form. There are no bubble-cells in the parenchyma. + + +15_a._ Var. subspinosa*, nov. + +This variety differs from the typical form in having its skeleton +spicules covered with minute irregular spines or conical projections. + +TYPES of both the typical form and the variety in the Indian Museum; +co-types of the typical form in the Trivandrum Museum. + +GEOGRAPHICAL DISTRIBUTION.--The same as that of the genus. +_Localities_:--Tenmalai, at the base of the western slopes of the W. +Ghats in Travancore (typical form) (_Annandale_); Ernakulam and Trichur +in Cochin (var. _subspinosa_) (_G. Mathai_). + +BIOLOGY.--My specimens, which were taken in November, were growing on +the roots of trees at the edge of an artificial pool by the roadside. +They were in rather dense shade, but their brilliant golden colour made +them conspicuous objects in spite of their small size. Mr. Mathai's +specimens from Cochin were attached to water-weeds and to the husk of a +cocoanut that had fallen or been thrown into the water. + + +Genus 3. EPHYDATIA, _Lamouroux_. + + _Ephydatia_, Lamouroux, Hist. des Polyp. corall. flex.* p. 6 + (_fide_ Weltner) (1816). + + _Ephydatia_, J. E. Gray, P. Zool. Soc. London. 1867, p. 550. + + _Trachyspongilla_, Dybowsky (_partim_), Zool. Anz. i, p. 53 + (1874). + + _Meyenia_, Carter (_partim_), Ann. Nat. Hist. (5) vii, p. 90 + (1881). + + _Carterella_, Potts & Mills (_partim_), P. Ac. Philad. 1881, + p. 150. + + _Ephydatia_, Vejdovsky, Abh. Boehm. Ges. xii, p. 23 (1883). + + _Meyenia_, Potts (_partim_), _ibid._ 1887, p. 210. + + _Carterella_, _id._ (_partim_), _ibid._ 1887, p. 260. + + _Ephydatia_, Weltner (_partim_), Arch. Naturg. lxi (i), p. + 121 (1895). + + _Ephydatia_, Annandale, P. U.S. Mus. xxxvii, p. 404 (1909). + +TYPE, (?) _Spongilla fluviatilis_, auctorum. + +This genus is separated from _Spongilla_ by the structure of the +gemmule-spicules, which bear at either end a transverse disk with +serrated or deeply notched edges, or at any rate with edges that are +distinctly undulated. The disks are equal and similar. True +flesh-spicules are usually absent, but more or less perfect birotulates +exactly similar to those associated with the gemmules are often found +free in the parenchyma. The skeleton is never very stout and the +skeleton-spicules are usually slender. + +As has been already stated, some authors consider _Ephydatia_ as the +type-genus of a subfamily distinguished from the subfamily of which +_Spongilla_ is the type-genus by having rotulate gemmule-spicules. The +transition between the two genera, however, is a very easy one. Many +species of the subgenus _Euspongilla_, the typical subgenus of +_Spongilla_ (including _S. lacustris_, the type-species of the genus), +have the spines at the ends of the gemmule-spicules arranged in such a +way as to suggest rudimentary rotules, while in the typical form of _S. +crateriformis_ this formation is so distinct that the species has +hitherto been placed in the genus _Ephydatia_ (_Meyenia_), although in +some sponges that agree otherwise with the typical form of the species +the gemmule-spicules are certainly not rotulate and in none do these +spicules bear definite disks. + +GEOGRAPHICAL DISTRIBUTION.--_Ephydatia_, except _Spongilla_, is the most +generally distributed genus of the Spongillidae, but in most countries it +is not prolific in species. In Japan, however, it appears to predominate +over _Spongilla_. Only one species is known from India, but another (_E. +blembingia_*, Evans) has been described from the Malay Peninsula, while +Weber found both the Indian species and a third (_E. bogorensis_*) in +the Malay Archipelago. + + +16. Ephydatia meyeni* (_Carter_). + + _Spongilla meyeni_, Carter, J. Bomb. Asiat. Soc. iii, p. 33, + pl. i, fig. 1, & Ann. Nat. Hist. (2) iv, p. 84, pl. iii, + fig. 1 (1849). + + _Spongilla meyeni_, Bowerbank, P. Zool. Soc. London, 1863, + p. 448, pl. xxxviii, fig. 4. + + _Spongilla meyeni_, Carter, Ann. Nat. Hist. (5) vii, p. 93 + (1881). + + _Ephydatia fluviatilis_, Weber, Zool. Ergeb. Niederlaend. + Ost-Ind. i. pp. 32, 46 (1890). + + _Ephydatia muelleri_, Weltner (_partim_), Arch. Naturg. lxi + (i), p. 125 (1895). + + _Ephydatia robusta_, Annandale, J. Asiat. Soc. Bengal, 1907, + p. 24, fig. 7. + + _Ephydatia muelleri_ subsp. _meyeni_, _id._, Rec. Ind. Mus. + ii, p. 306 (1908). + +_Sponge_ hard and firm but easily torn, usually of a clear white, +sometimes tinged with green, forming irregular sheets or masses never of +great thickness, without branches but often with stout subquadrate +projections, the summits of which are marked with radiating grooves; the +whole surface often irregularly nodulose and deeply pitted; the oscula +inconspicuous; the membrane adhering closely to the parenchyma. _The +parenchyma contains numerous bubble-cells_ (see p. 31, fig. 2). + +_Skeleton_ dense but by no means regular; the radiating fibres distinct +and containing a considerable amount of spongin, at any rate in the +outer part of the sponge; transverse fibres hardly distinguishable, +single spicules and irregular bundles of spicules taking their place. + +[Illustration: Fig. 21.--Gemmule and spicules of _Ephydatia meyeni_ +(from Calcutta). _a_, Skeleton-spicules; _b_, gemmule-spicules.] + +_Spicules._ Skeleton-spicules entirely smooth, moderately stout, feebly +curved, sharply pointed. No flesh-spicules. Gemmule-spicules with the +shaft as a rule moderately stout, much longer than the diameter of one +disk, smooth or with a few stout, straight horizontal spines, which are +frequently bifid or trifid; the disks flat, of considerable size, with +their margins cleanly and deeply divided into a comparatively small +number of deep, slender, triangular processes of different sizes; the +shaft extending not at all or very little beyond the disks. + +_Gemmules_ spherical, usually numerous and of rather large size; each +covered by a thick layer of minute air-spaces, among which the +gemmule-spicules are arranged vertically, often in two or even three +concentric series; a single short foraminal tubule; the pneumatic coat +confined externally by a delicate membrane, with small funnel-shaped +pits over the spicules of the outer series. + +I think that the gemmules found by me in Bhim Tal and assigned to +Potts's _Meyenia robusta_ belong to this species, but some of the +spicules are barely as long as the diameter of the disks. In any case +Potts's description is so short that the status of his species is +doubtful. His specimens were from N. America. + +_E. meyeni_ is closely related to the two commonest Holarctic species of +the genus, _E. fluviatilis_ and _E. muelleri_, which have been confused +by several authors including Potts. From _E. fluviatilis_ it is +distinguished by the possession of bubble-cells in the parenchyma, and +from _E. muelleri_ by its invariably smooth skeleton-spicules and the +relatively long shafts of its gemmule-spicules. The latter character is +a marked feature of the specimens from the Malay Archipelago assigned by +Prof. Max Weber to _E. fluviatilis_; I am indebted to his kindness for +an opportunity of examining some of them. + +TYPE in the British Museum; a fragment in the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--India and Sumatra. _Localities_:--BENGAL, +Calcutta and neighbourhood (_Annandale_); MADRAS PRESIDENCY, Cape +Comorin, Travancore (_Trivandrum Mus._): BOMBAY PRESIDENCY, Island of +Bombay (_Carter_): HIMALAYAS, Bhim Tal, Kumaon (alt. 4,500 feet) +(_Annandale_). + +BIOLOGY.--My experience agrees with Carter's, that this species is never +found on floating objects but always on stones or brickwork. It grows in +the Calcutta "tanks" on artificial stonework at the edge of the water, +together with _Spongilla carteri_, _S. alba_, _S. fragilis_ subsp. +_calcuttana_, and _Trochospongilla latouchiana_. It flourishes during +the cold weather and often occupies the same position in succeeding +years. In this event the sponge usually consists of a dead base, which +is of a dark brownish colour and contains no cells, and a living upper +layer of a whitish colour. + +The larva of _Sisyra indica_ is sometimes found in the canals, but the +close texture of the sponge does not encourage the visits of other +_incolae_. + + +Genus 4. DOSILIA, _Gray_. + + _Dosilia_, J. E. Gray, P. Zool. Soc. London, 1867, p. 550. + +TYPE, _Spongilla plumosa_, Carter. + +This genus is distinguished from _Ephydatia_ by the nature of the free +microscleres, the microscleres of the gemmule being similar in the two +genera. The free microscleres consist as a rule of several or many +shafts meeting together in several or many planes at a common centre, +which is usually nodular. The free ends of these shafts often possess +rudimentary rotulae. Occasionally a free microsclere may be found that is +a true monaxon and sometimes such spicules are more or less distinctly +birotulate. The skeleton is also characteristic. It consists mainly of +radiating fibres which bifurcate frequently in such a way that a +bush-like structure is produced. Transverse fibres are very feebly +developed and are invisible to the naked eye. Owing to the structure of +the skeleton the sponge has a feathery appearance. + +Gray originally applied the name _Dosilia_ to this species and to +_"Spongilla" baileyi_, Bowerbank. It is doubtful how far his generic +description applies to the latter, which I have not seen; but although +the position of _"Spongilla" baileyi_ need not be discussed here, I may +say that I do not regard it as a congener of _Dosilia plumosa_, the free +microscleres of which are of a nature rare but not unique in the family. +With _Dosilia plumosa_ we must, in any case, associate in one genus the +two forms that have been described as varieties, viz., _palmeri_*, Potts +from Texas and Mexico, and _brouini_*, Kirkpatrick from the White Nile. +By the kindness of the authorities of the Smithsonian Institution and +the British Museum I have been able to examine specimens of all three +forms, in each case identified by the author of the name, and I am +inclined to regard them as three very closely allied but distinct +species. Species with free microscleres similar to those of these three +forms but with heterogeneous or tubelliform gemmule-spicules will +probably need the creation of a new genus or new genera for their +reception. + +GEOGRAPHICAL DISTRIBUTION.--The typical species occurs in Bombay and +Madras; _D. palmeri_ has probably an extensive range in the drier parts +of Mexico and the neighbouring States, while _D. brouini_ has only been +found on the banks of the White Nile above Khartoum, in Tropical Africa. + + +17. Dosilia plumosa* (_Carter_). + + _Spongilla plumosa_, Carter, J. Bomb. Asiat. Soc. iii, p. + 34, pl. i, fig. 2, & Ann. Nat. Hist. (2) iv, p. 85, pl. iii, + fig. 2 (1849). + + _Spongilla plumosa_, Bowerbank, P. Zool. Soc. London, 1863, + p. 449, pl. xxxviii, fig. 5. + + _Dosilia plumosa_, J. E. Gray, _ibid._ 1867, p. 551. + + _Meyenia plumosa_, Carter, Ann. Nat. Hist. (5) vii, p. 94, + pl. v, fig. 6 (1881). + + _Meyenia plumosa_, Potts, P. Ac. Philad. 1887, p. 233. + + _Ephydatia plumosa_, Weltner, Arch. Naturg. lxi (i), p. 126 + (1895). + + _Ephydatia plumosa_, Petr, Rozp. Ceske Ak. Praze, Trida ii, + pl. ii, figs. 29, 30 (text in Czech) (1899). + +_Sponge_ forming soft irregular masses which are sometimes as much as 14 +cm. in diameter, of a pale brown or brilliant green colour; no branches +developed but the surface covered with irregular projections usually of +a lobe-like nature. + +_Skeleton_ delicate, with the branches diverging widely, exhibiting the +characteristic structure of the genus in a marked degree, containing a +considerable amount of chitin, which renders it resistant in spite of +its delicacy. + +_Spicules._ Skeleton-spicules smooth, sharply pointed, nearly straight, +moderately slender, about twenty times as long as their greatest +transverse diameter. Flesh-spicules occasionally amphioxous or +birotulate and with a single shaft, more frequently consisting of many +shafts meeting in a distinct central nodule, which is itself smooth; the +shafts irregularly spiny, usually more or less nodular at the tip, which +often bears a distinct circle of recurved spines that give it a rotulate +appearance. Gemmule-spicules with long, slender, straight shafts, which +bear short, slender, straight, horizontal spines sparsely and +irregularly scattered over their surface; the rotulae distinctly convex +when seen in profile; their edge irregularly and by no means deeply +notched; the shafts not extending beyond their surface but clearly seen +from above as circular umbones. + +[Illustration: Fig. 22.--_Dosilia plumosa._ + +A=microscleres, x 240; B=gemmule as seen in optical section from +below, x 75. (From Rambha.)] + +_Gemmules._ Somewhat depressed, covered with a thick granular pneumatic +coat, in which the spicules stand erect; the single aperture depressed. +Each gemmule surrounded more or less distinctly by a circle or several +circles of flesh-spicules. + +TYPE in the British Museum; some fragments in the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--Bombay and Madras. Carter's specimens were +taken in the island of Bombay, mine at Rambha in the north-east of the +Madras Presidency. I have been unable to discover this species in the +neighbourhood of Calcutta, but it is apparently rare wherever it occurs. + +BIOLOGY.--Carter writes as regards this species:--"This is the coarsest +and most resistant of all the species. As yet I have only found three or +four specimens of it, and these only in two tanks. I have never seen it +fixed on any solid body, but always floating on the surface of the +water, about a month after the first heavy rains of the S.W. monsoon +have fallen. Having made its appearance in that position, and having +remained there for upwards of a month, it then sinks to the bottom. That +it grows like the rest, adherent to the sides of the tank, must be +inferred from the first specimen which I found (which exceeds two feet +in circumference) having had a free and a fixed surface, the latter +coloured by the red gravel on which it had grown. I have noticed it +growing, for two successive years in the month of July, on the surface +of the water of one of the two tanks in which I have found it, and would +account for its temporary appearance in that position, in the following +way, viz., that soon after the first rains have fallen, and the tanks +have become filled, all the sponges in them appear to undergo a partial +state of putrescency, during which gas is generated in them, and +accumulates in globules in their structure, through which it must burst, +or tear them from their attachments and force them to the surface of the +water. Since then the coarse structure of _plumosa_ would appear to +offer greater resistance to the escape of this air, than that of any of +the other species, it is probable that this is the reason of my having +hitherto only found it in the position mentioned." + +It seems to me more probable that the sponges are actually broken away +from their supports by the violence of the rain and retain air +mechanically in their cavities. The only specimens of _D. plumosa_ that +I have seen alive were attached very loosely to their support. In +writing of the "coarse structure" of this species, Carter evidently +alludes to the wide interspaces between the component branches of the +skeleton. + +My specimens were attached to the stem of a water-lily growing in a pool +of slightly brackish water and were of a brilliant green colour. I +mistook them at first for specimens of _S. lacustris_ subsp. +_reticulata_ in which the branches had not developed normally. They were +taken in March and were full of gemmules. The pool in which they were +growing had already begun to dry up. + + +Genus 5. TROCHOSPONGILLA, _Vejdovsky_. + + _Trochospongilla_, Vejdovsky, Abh. K. Boehm. Ges. Wiss. xii, + p. 31 (1883). + + _Trochospongilla_, Wierzejski, Arch. Slaves de Biologie, i, + p. 44 (1886). + + _Trochospongilla_, Vejdovsky, P. Ac. Philad. 1887, p. 176. + + _Meyenia_, Potts (_partim_), _ibid._ p. 210. + + _Tubella_, _id._ (_partim_), _ibid._, p. 248. + + _Meyenia_, Carter (_partim_), Ann. Nat. Hist. (5) vii, p. 90 + (1881). + + _Trochospongilla_, Weltner, in Zacharias's Tier- und + Pflanzenwelt, i, p. 215 (1891). + + _Trochospongilla_, _id._, Arch. Naturg. lxi (i), p. 120 + (1895). + + _Tubella_, _id._ (_partim_), _ibid._ p. 128. + +TYPE, _Spongilla erinaceus_, Ehrenberg. + +The characteristic feature of this genus is that the rotulae of the +gemmule-spicules, which are homogeneous, have smooth instead of serrated +edges. Their stem is always short and they are usually embedded in a +granular pneumatic coat. The sponge is small in most of the species as +yet known; in some species microscleres without rotulae are associated +with the gemmules. + +[Illustration: Fig. 23.--A=skeleton-spicule of _Trochospongilla +latouchiana_; A'=gemmule-spicule of the same species; B=gemmule of _T. +phillottiana_ as seen in optical section from above; B'=skeleton-spicule +of same species: A, A', B' x 240; B x 75. All specimens from Calcutta.] + +I think it best to include in this genus, as the original diagnosis +would suggest, all those species in which all the gemmule-spicules are +definitely birotulate and have smooth edges to their disks, confining +the name _Tubella_ to those in which the upper rotula is reduced to a +mere knob. Even in those species in which the two disks are normally +equal, individual spicules may be found in which the equality is only +approximate, while, on the other hand, it is by no means uncommon for +individual spicules in such species as _"Tubella" pennsylvanica_, which +is here included in _Trochospongilla_, to have the two disks nearly +equal, although normally the upper one is much smaller than the lower. +There is very rarely any difficulty, however, in seeing at a glance +whether the edge of the disk is smooth or serrated, the only species in +which this difficulty would arise being, so far as I am aware, the +Australian _Ephydatia capewelli_* (Haswell), the disks of which are +undulated and nodulose rather than serrated. + +GEOGRAPHICAL DISTRIBUTION.--The genus includes so large a proportion of +small, inconspicuous species that its distribution is probably known but +imperfectly. It would seem to have its headquarters in N. America but +also occurs in Europe and Asia. In India three species have been found, +one of which (_T. pennsylvanica_) has an extraordinarily wide and +apparently discontinuous range, being common in N. America, and having +been found in the west of Ireland, the Inner Hebrides, and near the west +coast of S. India. The other two Indian species are apparently of not +uncommon occurrence in eastern India and Burma. + + + _Key to the Indian Species of_ Trochospongilla. + + I. Rotules of the gemmule-spicules equal + or nearly so. + A. Skeleton-spicules smooth, usually + pointed _latouchiana_, p. 115. + B. Skeleton-spicules spiny, blunt _phillottiana_, p. 117. + II. Upper rotule of the gemmule-spicules + distinctly smaller than the lower. + Skeleton-spicules spiny, pointed _pennsylvanica_, p. 118. + + +18. Trochospongilla latouchiana*, _Annandale_. + + _Trochospongilla latouchiana_, Annandale, J. Asiat. Soc. + Bengal, 1907, p. 21, fig. 5. + + _Trochospongilla latouchiana_, _id._, Rec. Ind. Mus. ii, p. + 157 (1908). + + _Trochospongilla leidyi_, _id._ (_nec_ Bowerbank), _ibid._ + iii, p. 103 (1909). + +[Illustration: Fig. 24.--_Trochospongilla latouchiana._ + +Vertical section of part of skeleton with gemmules _in situ_, x 30; also +a single gemmule, x 70. (From Calcutta).] + +_Sponge_ forming cushion-shaped masses rarely more than a few +centimetres in diameter or thickness and of a brown or yellow colour, +hard but rather brittle; surface evenly rounded, minutely hispid; oscula +inconspicuous, small, circular, depressed, very few in number; external +membrane adhering closely to the parenchyma; a chitinous membrane at the +base of the sponge. Larger sponges divided into several layers by +similar membranes. + +_Skeleton_ dense, forming a close reticulation; radiating fibres slender +but quite distinct, running up right through the sponge, crossed at +frequent intervals by single spicules or groups of spicules. + +_Spicules._ Skeleton-spicules smooth, about twenty times as long as the +greatest transverse diameter, as a rule sharply pointed; smooth +amphistrongyli, which are often inflated in the middle, sometimes mixed +with them but never in large numbers. No flesh-spicules. +Gemmule-spicules with the rotulae circular or slightly asymmetrical, flat +or nearly flat, marked with a distinct double circle as seen from above, +sometimes not quite equal; the shaft not projecting beyond them; the +diameter of the rotule 4-1/2 to 5 times that of the shaft, which is +about 2-2/3 times as long as broad. + +_Gemmules_ small (0.2 x 0.18 mm.), as a rule very numerous and scattered +throughout the sponge, flask-shaped, clothed when mature with a thin +microcell coat in which the birotulates are arranged with overlapping +rotulae, their outer rotulae level with the surface; foraminal aperture +circular, situated on an eminence. + + + _Average Measurements._ + + Diameter of gemmule 0.2 x 0.18 mm. + Length of skeleton-spicule 0.28 " + Length of birotulate-spicule 0.175 " + Diameter of rotula 0.02 " + +_T. latouchiana_ is closely related to _T. leidyi_ (Bowerbank) from N. +America, but is distinguished by its much more slender +skeleton-spicules, by the fact that the gemmules are not enclosed in +cages of megascleres or confined to the base of the sponge, and by +differences in the structure of the skeleton. + +TYPE in the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--Lower Bengal and Lower Burma. +_Localities_:--BENGAL, Calcutta and neighbourhood (_Annandale_): BURMA, +Kawkareik, Amherst district, Tenasserim (_Annandale_). + +BIOLOGY.--This species, which is common in the Museum tank, Calcutta, is +apparently one of those that can grow at any time of year, provided that +it is well covered with water. Like _T. leidyi_ it is capable of +producing fresh layers of living sponge on the top of old ones, from +which they are separated by a chitinous membrane. These layers are not, +however, necessarily produced in different seasons, for it is often +clear from the nature of the object to which the sponge is attached that +they must all have been produced in a short space of time. What appears +to happen in most cases is this:--A young sponge grows on a brick, the +stem of a reed or some other object at or near the edge of a pond, the +water in which commences to dry up. As the sponge becomes desiccated its +cells perish. Its gemmules are, however, retained in the close-meshed +skeleton, which persists without change of form. A heavy shower of rain +then falls, and the water rises again over the dried sponge. The +gemmules germinate immediately and their contents spread out over the +old skeleton, secrete a chitinous membrane and begin to build up a new +sponge. The process may be repeated several times at the change of the +seasons or even during the hot weather, or after a "break in the rains." +If, however, the dried sponge remains exposed to wind and rain for more +than a few months, it begins to disintegrate and its gemmules are +carried away to other places. Owing to their thin pneumatic coat and +relatively heavy spicules they are not very buoyant. Even in the most +favourable circumstances the sponge of _T. latouchiana_ never forms +sheets of great area. In spite of its rapid growth it is frequently +overgrown by _Spongilla carteri_. + + +19. Trochospongilla phillottiana*, _Annandale_. + + _Trochospongilla phillottiana_, Annandale, J. Asiat. Soc. + Bengal, 1907, p. 22, fig. 6. + + _Trochospongilla phillottiana_, _id._, Rec. Ind. Mus. i, p. + 269 (1907). + + _Trochospongilla phillottiana_, _id._, _ibid._ ii, p. 157 + (1908). + +_Sponge_ hard but friable, forming sheets or patches often of great +extent but never more than about 5 mm. thick; the surface minutely +hispid, flat; colour pale yellow, the golden-yellow gemmules shining +through the sponge in a very conspicuous manner; oscula inconspicuous; +external membrane adherent; no basal chitinous membrane. + +_Skeleton_ dense but by no means strong; the reticulation close but +produced mainly by single spicules, which form triangular meshes; +radiating fibres never very distinct, only persisting for a short +distance in a vertical direction; each gemmule enclosed in an open, +irregular cage of skeleton-spicules. + +_Spicules._ Skeleton-spicules short, slender, blunt, more or less +regularly and strongly spiny, straight or feebly curved. No +flesh-spicules. Gemmule-spicules with the rotulae circular, very wide as +compared with the shaft, concave on the surface, with the shaft +projecting as an umbo on the surface; the lower rotula often a little +larger than the upper. + +_Gemmules_ numerous, situated at the base of the sponge in irregular, +one-layered patches, small (0.32 x 0.264 mm.), of a brilliant golden +colour, distinctly wider than high, with a single aperture situated on +an eminence on the apex, each clothed (when mature) with a pneumatic +coat that contains relatively large but irregular air-spaces among which +the spicules stand with the rotulae overlapping alternately, a +funnel-shaped pit in the coat descending from the surface to the upper +rotula of each of them; the surface of the gemmule covered with +irregular projections. + + Diameter of gemmule 0.32 x 0.264 mm. + Length of skeleton-spicule 0.177 " + Length of gemmule-spicule 0.015 " + Diameter of rotule 0.022 " + +This species appears to be related to _T. pennsylvanica_, from which it +differs mainly in the form of its gemmule-spicules and the structure of +its gemmule. My original description was based on specimens in which the +gemmule-spicules were not quite mature. + +TYPE in the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--Lower Bengal and Lower Burma. +_Localities_:--BENGAL, Calcutta (_Annandale_): BURMA, jungle pool near +Kawkareik, Amherst district, Tenasserim (_Annandale_). + +BIOLOGY.--This species covers a brick wall at the edge of the Museum +tank in Calcutta every year during the "rains." In the cold weather the +wall is left dry, but it is usually submerged to a depth of several feet +before the middle of July. It is then rapidly covered by a thin layer of +the sponge, which dies down as soon as the water begins to sink when the +"rains" are over. For some months the gemmules adhere to the wall on +account of the cage of spicules in which each of them is enclosed, but +long before the water rises again the cages disintegrate and the +gemmules are set free. Many of them fall or are carried by the wind into +the water, on the surface of which, owing to their thick pneumatic coat, +they float buoyantly. Others are lodged in cavities in the wall. On the +water the force of gravity attracts them to one another and to the edge +of the pond, and as the water rises they are carried against the wall +and germinate. In thick jungle at the base of the Dawna Hills near +Kawkareik[AI] in the interior of Tenasserim, I found the leaves of +shrubs which grew round a small pool, covered with little dry patches of +the sponge, which had evidently grown upon them when the bushes were +submerged. This was in March, during an unusually severe drought. + + [Footnote AI: This locality is often referred to in + zoological literature as Kawkare_et_ or Kawkari_t_, or even + K_o_kari_t_.] + + +20. Trochospongilla pennsylvanica* (_Potts_). + + _Tubella pennsylvanica_, Potts, P. Ac. Philad. 1882, p. 14. + + _Tubella pennsylvanica_, _id._, _ibid._ 1887, p. 251, pl. + vi, fig. 2, pl. xii, figs. 1-3. + + _Tubella pennsylvanica_, Mackay, Trans. Roy. Soc. Canada, + 1889, Sec. iv, p. 95. + + _Tubella pennsylvanica_, Hanitsch, Nature, li, p. 511 + (1895). + + _Tubella pennsylvanica_, Weltner, Arch. Naturg. lxi (i), p. + 128 (1895). + + _Tubella pennsylvanica_, Hanitsch, Irish Natural. iv, p. 129 + (1895). + + _Tubella pennsylvanica_, Annandale, J. Linn. Soc., Zool., + xxx, p. 248 (1908). + + _Tubella pennsylvanica_, _id._, Rec. Ind. Mus. iii, p. 102 + (1909). + + _Tubella_ _pennsylvanica_, _id._, P. U.S. Mus. xxxvii, p. + 403, fig. 2 (1909). + +_Sponge_ soft, fragile, forming small cushion-shaped masses, grey or +green; oscula few in number, often raised on sloping eminences +surrounded by radiating furrows below the external membrane; external +membrane adhering to the parenchyma. + +_Skeleton_ close, almost structureless. "Surface of mature specimens +often found covered with parallel skeleton spicules, not yet arranged to +form cell-like interspaces" (_Potts_). + +_Spicules._ Skeleton-spicules slender, cylindrical, almost straight, +sharp or blunt, minutely, uniformly or almost uniformly spined; spines +sometimes absent at the tips. No flesh-spicules. Gemmule-spicules with +the lower rotula invariably larger than the upper; both rotulae flat or +somewhat sinuous in profile, usually circular but sometimes asymmetrical +or subquadrate in outline, varying considerably in size. + +_Gemmules_ small, numerous or altogether absent, covered with a granular +pneumatic coat of variable thickness; the rotulae of the gemmule-spicules +overlapping and sometimes projecting out of the granular coat. + +The measurements of the spicules and gemmules of an Indian specimen and +of one from Lehigh Gap, Pennsylvania, are given for comparison:-- + + Travancore. Pennsylvania. + Length of skeleton-spicules 0.189-0.242 mm. 0.16-0.21 mm. + (average 0.205 mm.) (average 0.195 mm.) + Breadth " " 0.0084-0.0155 mm. 0.0084 mm. + Length of birotulate 0.0126 " 0.0099 " + Diameter of upper rotula 0.0084 " 0.0084 " + " lower " 0.0169 " 0.0168 " + " gemmule 0.243-0.348 mm. 0.174-0.435 mm. + +The spicules of the Travancore specimen are, therefore, a trifle larger +than those of the American one, but the proportions are closely similar. + +The difference between the gemmule-spicules of this species and those of +such a form as _T. phillottiana_ is merely one of degree and can hardly +be regarded as a sufficient justification for placing the two species in +different genera. If, as I have proposed, we confine the generic name +_Tubella_ to those species in which the gemmule-spicules are really like +"little trumpets," the arrangement is a much more natural one, for these +species have much in common apart from the gemmule-spicules. _T. +pennsylvanica_ does not appear to be very closely related to any other +known species except _T. phillottiana_. + +TYPE in the U.S. National Museum, from which specimens that appear to be +co-types have been sent to the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--Very wide and apparently discontinuous:--N. +America (widely distributed), Ireland (_Hanitsch_), Hebrides of Scotland +(_Annandale_), Travancore, S. India (_Annandale_). The only Indian +locality whence I have obtained specimens is Shasthancottah Lake near +Quilon in Travancore. + +BIOLOGY.--In Shasthancottah Lake _T. pennsylvanica_ is found on the +roots of water-plants that are matted together to form floating islands. +It appears to avoid light and can only be obtained from roots that have +been pulled out from under the islands. In Scotland I found it on the +lower surface of stones near the edge of Loch Baa, Isle of Mull. In such +circumstances the sponge is of a greyish colour, but specimens of the +variety _minima_ taken by Potts on rocks and boulders in Bear Lake, +Pennsylvania, were of a bright green. + +Sponges taken in Travancore in November were full of gemmules; in my +Scottish specimens (taken in October) I can find no traces of these +bodies, but embryos are numerous. + + +Genus 6. TUBELLA, _Carter_. + + _Tubella_, Carter, Ann. Nat. Hist. (5) vii, p. 96 (1881). + + _Tubella_, Potts (_partim_), P. Ac. Philad. 1887, p. 248. + + _Tubella_, Weltner (_partim_), Arch. Naturg. lxi (i), p. 128 + (1895). + +TYPE, _Spongilla paulula_, Bowerbank. + +This genus is distinguished from _Ephydatia_ and _Trochospongilla_ by +the fact that the two ends of the gemmule-spicules are unlike not only +in size but also in form. It sometimes happens that this unlikeness is +not so marked in some spicules as in others, but in some if not in all +the upper end of the shaft (that is to say the end furthest removed from +the inner coat of the gemmule in the natural position) is reduced to a +rounded knob, while the lower end expands into a flat transverse disk +with a smooth or denticulated edge. The spicule thus resembles a little +trumpet resting on its mouth. The shaft of the spicule is generally +slender and of considerable length. The skeleton of the sponge is as a +rule distinctly reticulate and often hard; the skeleton-spicules are +either slender or stout and sometimes change considerably in proportions +and outline as they approach the gemmules. + +GEOGRAPHICAL DISTRIBUTION.--The genus is widely distributed in the +tropics of both Hemispheres, its headquarters apparently being in S. +America; but it is nowhere rich in species. Only two are known from the +Oriental Region, namely _T. vesparium_* from Borneo, and _T. +vesparioides_* from Burma. + + +21. Tubella vesparioides*, _Annandale_. (Plate II, fig. 4.) + + _Tubella vesparioides_, Annandale, Rec. Ind. Mus. ii, p. 157 + (1908). + +_Sponge_ forming rather thick sheets of considerable size, hard but +brittle, almost black in colour; oscula inconspicuous; external membrane +supported on a reticulate horizontal skeleton. + +_Skeleton._ The surface covered with a network of stout spicule-fibres, +the interstices of which are more or less deeply sunk, with sharp fibres +projecting vertically upwards at the nodes; the whole mass pervaded by a +similar network, which is composed of a considerable number of spicules +lying parallel to one another, overlapping at the ends and bound +together by a profuse secretion of spongin. + +[Illustration: Fig. 25.--Spicules of _Tubella vesparioides_ (from type +specimen). x 240.] + +_Spicules._ Skeleton-spicules slender, smooth, amphioxous, bent in a +wide arc or, not infrequently, at an angle. No true flesh-spicules. +Gemmule-spicules terminating above in a rounded, knob-like structure and +below in a relatively broad, flat rotula, which is very deeply and +irregularly indented round the edge when mature, the spicules at an +earlier stage of development having the form of a sharp pin with a round +head; shaft of adult spicules projecting slightly below the rotula, +long, slender, generally armed with a few stout conical spines, which +stand out at right angles to it. + +_Gemmules_ numerous throughout the sponge, spherical, provided with a +short, straight foraminal tubule, surrounded by one row of spicules, +which are embedded in a rather thin granular coat. + + Average length of skeleton-spicule 0.316 mm. + " breadth of skeleton-spicule 0.0135 " + " length of gemmule-spicule 0.046 " + " diameter of rotula 0.0162 " + " " gemmule 0.446 " + +This sponge is closely related to _Tubella vesparium_ (v. Martens) from +Borneo, from which it may be distinguished by its smooth +skeleton-spicules and the deeply indented disk of its gemmule-spicules. +The skeleton-fibres are also rather less stout. By the kindness of Dr. +Weltner, I have been able to compare types of the two species. + +TYPE in the Indian Museum. + +HABITAT.--Taken at the edge of the Kanghyi ("great pond") at Mudon near +Moulmein in the Amherst district of Tenasserim. The specimens were +obtained in March in a dry state and had grown on logs and branches +which had evidently been submerged earlier in the year. The name +_vesparium_ given to the allied species on account of its resemblance to +a wasps' nest applies with almost equal force to this Burmese form. + + +Genus 7. CORVOSPONGILLA, nov. + +TYPE[AJ], _Spongilla loricata_, Weltner. + + [Footnote AJ: Potts's _Spongilla novae-terrae_ from + Newfoundland and N. America cannot belong to this genus + although it has similar flesh-spicules, for, as Weltner has + pointed out (_op. cit. supra_ p. 126), the gemmule-spicules + are abortive rotulae. This is shown very clearly in the + figure published by Petr (Rozp. Ceske Ak. Praze, Trida, ii, + pl. ii, figs. 27, 28, 1899), who assigns the species to + _Heteromeyenia_. Weltner places it in _Ephydatia_, and it + seems to be a connecting link between the two genera. It has + been suggested that it is a hybrid (Traxler, Termes. + Fuzetek, xxi, p. 314, 1898).] + +Spongillidae in which the gemmule-spicules are without a trace of rotulae +and the flesh-spicules have slender cylindrical shafts that bear at or +near either end a circle of strong recurved spines. The gemmule-spicules +are usually stout and sausage-shaped, and the gemmules resemble those of +_Stratospongilla_ in structure. The skeleton is strong and the +skeleton-spicules stout, both resembling those of the "genus" +_Potamolepis_, Marshall. + +As in all other genera of Spongillidae the structure of the skeleton is +somewhat variable, the spicule-fibres of which it is composed being much +more distinct in some species than in others. The skeleton-spicules are +often very numerous and in some cases the skeleton is so compact and +rigid that the sponge may be described as stony. The flesh-spicules +closely resemble the gemmule-spicules of some species of _Ephydatia_ and +_Heteromeyenia_. + +GEOGRAPHICAL DISTRIBUTION.--The species of this genus are probably +confined to Africa (whence at least four are known) and the Oriental +Region. One has been recorded from Burma and another from the Bombay +Presidency. + + + _Key to the Indian Species of_ Corvospongilla. + + I. Gemmule with two layers of gemmule-spicules; + those of the inner layer not + markedly smaller than those of the outer. _burmanica_, p. 123. + + II. Gemmule with two layers of gemmule-spicules, + the outer of which contains + spicules of much greater size than the + inner. _lapidosa_, p. 124. + + +22. Corvospongilla burmanica* (_Kirkpatrick_). (Plate II, fig. 5.) + + _Spongilla loricata_ var. _burmanica_, Kirkpatrick, Rec. + Ind. Mus. ii, p. 97, pl. ix (1908). + +_Sponge_ forming a shallow sheet, hard, not very strong, of a pale +brownish colour; the surface irregularly spiny; the oscula small but +conspicuous, circular, raised on little turret-like eminences; the +external membrane adhering closely to the sponge. + +_Skeleton_ dense but by no means regular; the network composed largely +of single spines; thick radiating fibres distinguishable in the upper +part of the sponge. + +_Spicules._ Skeleton-spicules smooth, not very stout, amphistrongylous, +occasionally a little swollen at the ends, often with one or more +fusiform swellings, measuring on an average about 0.27 x 0.0195 mm. +Flesh-spicules with distinct rotules, the recurved spines numbering 4 to +6, measuring about 1/7 the length of the spicules; the shaft by no means +strongly curved; their length from 0.03-0.045 mm. Gemmule-spicules +amphioxous, as a rule distinctly curved, sometimes swollen at the ends, +covered regularly but somewhat sparsely with fine spines, not measuring +more than 0.49 x 0.078 mm. + +_Gemmules_ strongly adherent, arranged in small groups, either single or +double; when single spherical, when double oval; each gemmule or pair of +gemmules covered by two layers of gemmule-spicules bound together in +chitinous substance; the inner layer on the inner coat of the gemmule, +the outer one separated from it by a space and in contact with the outer +cage of skeleton-spicules; the size of the gemmule-spicules variable in +both layers; external to the outer layer a dense cage of +skeleton-spicules; foraminal tubule short, cylindrical. + +This sponge is closely related to _S. loricata_, Weltner, of which +Kirkpatrick regards it as a variety. "The main difference," he writes, +"between the typical African form and the Burmese variety consists in +the former having much larger microstrongyles (83 x 15.7 mu [0.83 x 0.157 +mm.]) with larger and coarser spines;... Judging from Prof. Weltner's +sections of gemmules, these bodies lack the definite outer shell of +smooth macrostrongyles [blunt skeleton-spicules], though this may not +improbably be due to the breaking down and removal of this layer. A +further difference consists in the presence, in the African specimen, of +slender, finely spined strongyles [amphistrongyli], these being absent +in the Burmese form, though perhaps this fact is not of much +importance." + +TYPE in the British Museum; a piece in the Indian Museum. + +HABITAT.--Myitkyo, head of the Pegu-Sittang canal, Lower Burma (_E. W. +Oates_). + +BIOLOGY.--The sponge had grown over a sheet of the polyzoon _Hislopia +lacustris_, Carter (see p. 204), remains of which can be detected on its +lower surface. + +"Mr. E. W. Oates, who collected and presented the sponge, writes that +the specimen was found encrusting the vertical and horizontal surfaces +of the bottom beam of a lock gate, where it covered an area of six +square feet. The beam had been tarred several times before the sponge +was discovered. The portion of the gate on which the sponge was growing +was submerged from November to May for eight hours a day at spring +tides, but was entirely dry during the six days of neap tides. From May +to October it was constantly submerged. The sponge was found in April. +Although the canal is subject to the tides, the water at the lock is +always fresh. The colour of the sponge during life was the same as in +its present condition." + + +23. Corvospongilla lapidosa* (_Annandale_). + + _Spongilla lapidosa_ Annandale, Rec. Ind. Mus. ii, pp. 25, + 26, figs. 3, 4, 5 (1908). + +The _sponge_ forms a thin but extremely hard and resistant crust the +surface of which is either level, slightly concave, or distinctly +corrugated; occasional groups of spicules project from it, but their +arrangement is neither so regular nor so close as is the case in _C. +burmanica_. The dermal membrane adheres closely to the sponge. The +oscula are small; some of them are raised above the general surface but +not on regular turret-shaped eminences. The colour is grey or black. +There is a thick chitinous membrane at the base of the sponge. + +[Illustration: Fig. 26.--Spicules of _Corvospongilla lapidosa_ (from +type specimen), x 240.] + +The _skeleton_ is extremely dense owing to the large number of spicules +it contains, but almost structureless; broad vertical groups of spicules +occur but lack spongin and only traverse a small part of the thickness +of the sponge; their position is irregular. The firmness of the skeleton +is due almost entirely to the interlocking of individual spicules. At +the base of the sponge the direction of a large proportion of the +spicules is horizontal or nearly horizontal, the number arranged +vertically being much greater in the upper part. + +_Spicules._ The skeleton-spicules are sausage-shaped and often a little +swollen at the ends or constricted in the middle. A large proportion are +twisted or bent in various ways, and a few bear irregular projections or +swellings. The majority, however, are quite smooth. Among them a few +more or less slender, smooth amphioxi occur, but these are probably +immature spicules. The length and curvature of the amphistrongyli varies +considerably, but the average measurements are about 0.28 x 0.024 mm. +The flesh-spicules also vary greatly in length and in the degree to +which their shafts are curved. At first sight it seems to be possible to +separate them into two categories, one in which the shaft is about 0.159 +mm. long, and another in which it is only 0.05 mm. or even less; and +groups of birotulates of approximately the same length often occur in +the interstices of the skeleton. Spicules of all intermediate lengths +can, however, be found. The average diameter of the shaft is 0.0026 mm. +and of the rotula 0.0106 mm., and the rotula consists of from 6 to 8 +spines. The gemmule-spicules vary greatly in size, the longest measuring +about 0.08 x 0.014 and the smallest about 0.034 x 0.007 or even less. +There appears to be in their case an even more distinct separation as +regards size than there is in that of the flesh-spicules; but here again +intermediate forms occur. They are all stout, more or less blunt, and +more or less regularly covered with very short spines; most of them are +distinctly curved, but some are quite straight. + +_Gemmules._ The gemmules are firmly adherent to the support of the +sponge, at the base of which they are congregated in groups of four or +more. They vary considerably in size and shape, many of them being +asymmetrical and some elongate and sausage-shaped. The latter consist of +single gemmules and not of a pair in one case. Extreme forms measure +0.38 x 0.29 and 0.55 x 0.25. Each gemmule is covered with a thick +chitinous membrane in close contact with its wall and surrounding it +completely. This membrane is full of spicules arranged as in a mosaic; +most or all of them belong to the smaller type, and as a rule they are +fairly uniform in size. Separated from this layer by a considerable +interval is another layer of spicules embedded in a chitinous membrane +which is in continuity with the basal membrane of the sponge. The +spicules in this membrane mostly belong to the larger type and are very +variable in size; mingled with them are often a certain number of +birotulate flesh-spicules. The membrane is in close contact with a dense +cage of skeleton-spicules arranged parallel to it and bound together by +chitinous substance. The walls of this cage, when they are in contact +with those of the cages of other gemmules, are coterminous with them. +There is a single depressed aperture in the gemmules, as a rule situated +on one of the longer sides. + +This sponge is distinguished from _C. burmanica_ not only by differences +in external form, in the proportions of the spicules and the structure +of the skeleton, but also by the peculiar nature of the armature of the +gemmule. The fact that birotulate spicules are often found in close +association with them, is particularly noteworthy. + +TYPE in the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--This sponge has only been found in the +Western Ghats of the Bombay Presidency. _Localities_:--Igatpuri Lake and +the R. Godaveri at Nasik. + +BIOLOGY.--There is a remarkable difference in external form between the +specimens taken in Igatpuri and those from Nasik, and this difference is +apparently due directly to environment. In the lake, the waters of which +are free from mud, the sponges were growing on the lower surface of +stones near the edge. They formed small crusts not more than about 5 cm. +(2 inches) in diameter and of a pale greyish colour. Their surface was +flat or undulated gently, except round the oscula where it was raised +into sharply conical eminences with furrowed sides. The specimens from +Nasik, which is about 30 miles from Igatpuri, were attached, together +with specimens of _Spongilla cinerea_ and _S. indica_, to the sides of a +stone conduit full of very muddy running water. They were black in +colour, formed broad sheets and were markedly corrugated on the surface. +Their oscula were not raised on conical eminences and were altogether +most inconspicuous. The skeleton was also harder than that of sponges +from the lake. + +In the lake _C. lapidosa_ was accompanied by the gemmules of _Spongilla +bombayensis_, but it is interesting that whereas the latter sponge was +entirely in a resting condition, the former was in full vegetative +vigour, a fact which proves, if proof were necessary, that the similar +conditions of environment do not invariably have the same effect on +different species of Spongillidae. + + + APPENDIX TO PART I. + + FORM OF UNCERTAIN POSITION. + + (Plate I, fig. 4.) + +On more than one occasion I have found in my aquarium in Calcutta small +sponges of a peculiar type which I am unable to refer with certainty to +any of the species described above. Fig. 4, pl. I, represents one of +these sponges. They are never more than about a quarter of an inch in +diameter and never possess more than one osculum. They are +cushion-shaped, colourless and soft. The skeleton-spicules are smooth, +sharply pointed, moderately slender and relatively large. They are +arranged in definite vertical groups, which project through the dermal +membrane, and in irregular transverse formation. Small spherical +gemmules are present but have only a thin chitinous covering without +spicules or foramen. + +These sponges probably represent an abnormal form of some well-known +species, possibly of _Spongilla carteri_. I have seen nothing like them +in natural conditions. + + + + + PART II. + + FRESHWATER POLYPS + + (HYDRIDA). + + + + +INTRODUCTION TO PART II. + + +I. + +THE PHYLUM COELENTERATA AND THE CLASS HYDROZOA. + + +The second of the great groups or phyla into which the metazoa are +divided is the Coelenterata, in which are included most of the animals +commonly known as zoophytes, and also the corals, sea-anemones and +jelly-fish. These animals are distinguished from the sponges on the one +hand and from the worms, molluscs, arthropods, vertebrates, etc., on the +other by possessing a central cavity (the coelenteron or "hollow +inside") the walls of which are the walls of the body and consist of +_two_ layers of cells separated by a structureless, or apparently +structureless, jelly. This cavity has as a main function that of a +digestive cavity. + +An ideally simple coelenterate would not differ much in general +appearance from an olynthus (p. 27), but it would have no pores in the +body-wall and its upper orifice would probably be surrounded by +prolongations of the body-wall in the form of tentacles. There would be +no collar-cells, and the cells of the body generally would have a much +more fixed and definite position and more regular functions than those +of any sponge. The most characteristic of them would be the so-called +cnidoblasts. Each of these cells contains a capsule[AK] from which a +long thread-like body can be suddenly uncoiled and shot out. + + [Footnote AK: Similar capsules are found in the tissues of + certain worms and molluscs, but there is the strongest + evidence that these animals, which habitually devour + coelenterates, are able to swallow the capsules uninjured + and to use them as weapons of defence (see Martin, Q. J. + Micro. Sci. London, lii, p. 261, 1908, and Grosvenor, Proc. + Roy. Soc. London, lxxii, p. 462, 1903). The "trichocysts" of + certain protozoa bear a certain resemblance to the + nettle-cells of coelenterates and probably have similar + functions.] + +The simplest in structure of the coelenterates are those that constitute +the class Hydrozoa. In this class the primitive central cavity is not +divided up by muscular partitions and there is no folding in of the +anterior part of the body to form an oesophagus or stomatodaeum such as +is found in the sea-anemones and coral polyps. In many species and +genera the life-history is complex, illustrating what is called the +alternation of generations. That is to say, only alternate generations +attain sexual maturity, those that do so being produced as buds from a +sexless generation, which itself arises from the fertilized eggs of a +previous sexual generation. The sexual forms as a rule differ +considerably in structure from the sexless ones; many medusae are the +sexual individuals in a life-cycle in which those of the sexless +generation are sedentary. + +An excellent general account of the coelenterates will be found in the +Cambridge Natural History, vol. i (by Prof. Hickson). + + +STRUCTURE OF HYDRA. + +_Hydra_, the freshwater polyp, is one of the simplest of the Hydrozoa +both as regards structure and as regards life-history. Indeed, it +differs little as regards structure from the ideally simple coelenterate +sketched in a former paragraph, while its descent is direct from one +polyp to another, every generation laying its own eggs[AL]. The animal +may be described as consisting of the following parts:--(1) an upright +(or potentially upright) column or body, (2) a circle of contractile +tentacles at the upper extremity of the column, (3) an oral disk or +peristome surrounding the mouth and surrounded by the tentacles, and (4) +a basal or aboral disk at the opposite extremity. The whole animal is +soft and naked. The column, when the animal is at rest, is almost +cylindrical in some forms but in others has the basal part distinctly +narrower than the upper part. It is highly contractile and when +contracted sometimes assumes an annulate appearance; but as a rule the +external surface is smooth. + + [Footnote AL: The statement is not strictly accurate as + regards the Calcutta phase of _H. vulgaris_, for the summer + brood apparently does not lay eggs but reproduces its + species by means of buds only. This state of affairs, + however, is probably an abnormality directly due to + environment.] + +The tentacles vary in number, but are never very numerous. They are +disposed in a single circle round the oral disk and are hollow, each +containing a prolongation of the central cavity of the column. Like the +column but to an even greater degree they are contractile, and in some +forms they are capable of great elongation. They cannot seize any object +between them, but are able to move in all directions. + +The disk that surrounds the mouth, which is a circular aperture, is +narrow and can to some extent assume the form of a conical proboscis, +although this feature is never so marked as it is in some hydroids. The +basal disk is even narrower and is not splayed out round the edges. + +[Illustration: Fig. 27.--Nettle-cells of _Hydra_. + +A=capsules from nettle-cells of a single specimen of the summer phase of +_H. vulgaris_ from Calcutta, x 480: figures marked with a dash represent +capsules with barbed threads. B=a capsule with the thread discharged, +from the same specimen, x 480. C=capsule with barbed thread, from a +specimen of _H. oligactis_ from Lahore. D=undischarged nettle-cell of +_H. vulgaris_ from Europe (after Nussbaum, highly magnified). +E=discharged capsule of the same (after the same author). +_a_=cnidoblast; _b_=capsule; _c_=thread; _d_=cnidocil. Only the base of +the thread is shown in E.] + +A section through the body-wall shows it to consist of the three typical +layers of the coelenterates, viz., (i) an outer cellular layer of +comparatively small cells, the ectoderm; (ii) an intermediate, +structureless or apparently structureless layer, the mesogloea or +"central jelly"; and (iii) an internal layer or endoderm consisting of +relatively large cells. The cells of the ectoderm are not homogeneous. +Some of them possess at their base narrow and highly contractile +prolongations that exercise the functions of muscles. Others are +gland-cells and secrete mucus; others have round their margins delicate +ramifying prolongations and act as nerve-cells. Sense-cells, each of +which bears on its external surface a minute projecting bristle, are +found in connection with the nerve-cells, and also nettle-cells of more +than one type. + +The mesogloea is very thin. + +The endoderm consists mainly of comparatively large cells with polygonal +bases which can be seen from the external surface of the column in +colourless individuals. Their inner surface is amoeboid and in certain +conditions bears one or more vibratile cilia or protoplasmic lashes. +Nettle-cells are occasionally found in the endoderm, but apparently do +not originate in this layer. + +The walls of the tentacles do not differ in general structure from those +of the column, but the cells of the endoderm are smaller and the +nematocysts of the ectoderm more numerous, and there are other minor +differences. + +A more detailed account of the anatomy of _Hydra_ will be found in any +biological text-book, for instance in Parker's Elementary Biology; but +it is necessary here to say something more as regards the nettle-cells, +which are of great biological and systematic importance. + +A nettle-cell of the most perfect type and the structures necessary to +it consist of the following parts:-- + + (1) A true cell (the cnidoblast), which contains-- + (2) a delicate capsule full of liquid; + (3) a long thread coiled up in the capsule; and + (4) a cnidocil or sensory bristle, which projects from the + external surface of the cnidoblast. + +A nerve-cell is associated with each cnidoblast. + +In _Hydra_ the nettle-cells are of two distinct types, in one of which +the thread is barbed at the base, whereas in the other it is simple. +Both types have often two or more varieties and intermediate forms +occur, but generally speaking the capsules with simple threads are much +smaller than those with barbed ones. The arrangement of the nettle-cells +is not the same in all species of _Hydra_, but as a rule they are much +more numerous in the tentacles than elsewhere on the body, each large +cell being surrounded by several small ones. The latter are always much +more numerous than the former. + + +CAPTURE AND INGESTION OF PREY: DIGESTION. + +The usual food of _Hydra_ consists of small insect larvae, worms, and +crustacea, but the eggs of fish are also devoured. The method in which +prey is captured and ingested has been much disputed, but the following +facts appear to be well established. + +If a small animal comes in contact with the tentacles of the polyp, it +instantly becomes paralysed. If it adheres to the tentacle, it perishes; +but if, as is often the case, it does not do so, it soon recovers the +power of movement. Animals which do not adhere are generally those (such +as ostracod crustacea) which have a hard integument without weak spots. +Nematocysts of both kinds shoot out their threads against prey with +considerable violence, the discharge being effected, apparently in +response to a chemical stimulus, by the sudden uncoiling of the thread +and its eversion from the capsule. Apparently the two kinds of threads +have different functions to perform, for whereas there is no doubt that +the barbed threads penetrate the more tender parts of the body against +which they are hurled, there is evidence that the simple threads do not +do so but wrap themselves round the more slender parts. Nussbaum (Arch. +mikr. Anat. xxix, pl. xx, fig. 108) figures the tail of a _Cyclops_ +attacked by _Hydra vulgaris_ and shows several simple threads wrapped +round the hairs and a single barbed thread that has penetrated the +integument. Sometimes the cyst adheres to the thread and remains +attached to its cnidoblast and to the polyp, but sometimes the thread +breaks loose. Owing to the large mass of threads that sometimes +congregate at the weaker spots in the external covering of an animal +attacked (_e. g._, at the little sensory pits in the integument of the +dorsal surface of certain water-mites) it is often difficult to trace +out the whole length of any one thread, and as a thread still attached +to its capsule is frequently buried in the body of the prey, right up to +the barbs, while another thread that has broken loose from its capsule +appears immediately behind the fixed one, it seems as though the barbs, +which naturally point towards the capsule, had become reversed. This +appearance, however, is deceptive. The barbs are probably connected with +the discharge of the thread and do not function at all in the same way +as those on a spear- or arrow-head, never penetrating the object against +which the projectile is hurled. Indeed, their position as regards the +thread resembles that of the feathers on the shaft of an arrow rather +than that of the barb of the head. + +Adhesion between the tentacles and the prey is effected partly by the +gummy secretion of the glands of the ectoderm, which is perhaps +poisonous as well as adhesive, and partly by the threads. Once the prey +is fast and has ceased to struggle, it is brought to the mouth, which +opens wide to receive it, by the contraction and the contortions of the +tentacles, the column, and the peristome. At the same time a mass of +transparent mucus from the gastral cavity envelops it and assists in +dragging it in. There is some dispute as to the part played by the +tentacles in conveying food into the mouth. My own observations lead me +to think that, at any rate so far as _H. vulgaris_ is concerned, they do +not push it in, but sometimes in their contortions they even enter the +cavity accidentally. + +When the food has once been engulfed some digestive fluid is apparently +poured out upon it. In _H. vulgaris_ it is retained in the upper part of +the cavity and the soluble parts are here dissolved out, the insoluble +parts such as the chitin of insect larvae or crustacea being ejected from +the mouth. Digestion is, however, to a considerable extent +intracellular, for the cells of the endoderm have the power of thrusting +out from their surface lobular masses of their cell-substance in which +minute nutritive particles are enveloped and dissolved. The movements of +the cilia which can also be thrust out from and retracted into these +cells, keep the food in the gastral cavity in motion and probably turn +it round so as to expose all parts in turn to digestive action. Complete +digestion, at any rate in the Calcutta form, takes several days to +accomplish, and after the process is finished a flocculent mass of +colourless excreta is emitted from the mouth. + + +COLOUR. + +In _Hydra viridis_, a species that has not yet been found in India, the +green colour is due to the presence in the cells of green corpuscles +which closely resemble those of the cells of certain freshwater sponges. +They represent a stage in the life-cycle of _Chlorella vulgaris_, +Beyerinck[AM], an alga which has been cultivated independently. + + [Footnote AM: Bot. Zeitung, xlviii (1890): see p. 49, _antea_.] + +In other species of the genus colour is largely dependent on food, +although minute corpuscles of a _dark_ green shade are sometimes found +in the cells of _H. oligactis_. In the Calcutta phase of _H. vulgaris_ +colour is due entirely to amorphous particles situated mainly in the +cells of the endoderm. If the polyp is starved or exposed to a high +temperature, these particles disappear and it becomes practically +colourless. They probably form, therefore, some kind of food-reserve, +and it is noteworthy that a polyp kept in the unnatural conditions that +prevail in a small aquarium invariably becomes pale, and that its +excreta are not white and flocculent but contain dark granules +apparently identical with those found in the cells of coloured +individuals (p. 154). + +Berninger[AN] has just published observations on the effect of +long-continued starvation on _Hydra_ carried out in Germany. He finds +that the tentacles, mouth, and central jelly disappear, and that a +closed "bladder" consisting of two cellular layers remains; but, to +judge from his figures, the colour does not disappear in these +circumstances. + + [Footnote AN: Zool. Anz. xxxvi, pp. 271-279, figs., Oct. + 1910.] + + +BEHAVIOUR. + +_Hydra viridis_ is a more sluggish animal than the other species of its +genus and does not possess the same power of elongating its column and +tentacles. It is, nevertheless, obliged to feed more frequently. Wagner +(Quart. J. Micr. Sci. xlviii, p. 586, 1905) found it impossible to use +this species in his physiological experiments because it died of +starvation more rapidly than other forms. This fact is interesting in +view of the theory that the green corpuscles in the cells of _H. +viridis_ elaborate nutritive substances for its benefit. _H. vulgaris_, +at any rate in Calcutta, does not ordinarily capture prey more often +than about once in three days. + +All _Hydrae_ (except possibly the problematical _H. rubra_ of Roux, p. +160) spend the greater part of their time attached by the basal disk to +some solid object, but, especially in early life, _H. vulgaris_ is often +found floating free in the water, and all the species possess powers of +progression. They do not, however, all move in the same way. _H. +viridis_ progresses by "looping" like a geometrid caterpillar. During +each forward movement the column is arched downwards so that the +peristome is in contact with the surface along which the animal is +moving. The basal disk is then detached and the column is twisted round +until the basal disk again comes in contact with the surface at a point +some distance in advance of its previous point of attachment. The +manoeuvre is then repeated. _H. vulgaris_, when about to move, bends +down its column so that it lies almost prone, stretches out its +tentacles, which adhere near the tips to the surface (p. 153), detaches +its basal disk, and then contracts the tentacles. The column is dragged +forward, still lying almost prone, the basal disk is bent downwards and +again attached, and the whole movement is repeated. Probably _H. +oligactis_ moves in the same way. + +When _H. viridis_ is at rest the tentacles and column, according to +Wagner, exhibit rhythmical contractions in which those of the buds act +in sympathy with those of the parent. In _H. vulgaris_ no such movements +have been observed. This species, however, when it is waiting for prey +(p. 154) changes the direction of its tentacles about once in half an +hour. + +All species of _Hydra_ react to chemical and physical stimuli by +contraction and by movements of the column and tentacles, but if the +stimuli are constantly repeated, they lose the power to some extent. All +species are attracted by light and move towards the point whence it +reaches them. _H. vulgaris_, however, at any rate in India, is more +strongly repelled by heat. Consequently, if it is placed in a glass +vessel of water, on one side of which the sun is shining directly, it +moves away from the source of the light[AO]. But if the vessel be +protected from the direct rays of the sun and only a subdued light falls +on one side of it, the polyp moves towards that side. No species of the +genus is able to move in a straight line. Wilson (Amer. Natural. xxv, p. +426, 1891) and Wagner (_op. cit. supra_) have published charts showing +the elaborately erratic course pursued by a polyp in moving from one +point to another and the effect of light as regards its movements. + + [Footnote AO: Mr. F. H. Gravely tells me that this is also + the case as regards _H. viridis_ in England, at any rate if + freshly captured specimens are placed overnight in a bottle + in a window in such a position that the early morning + sunlight falls upon one side of the bottle.] + +If an individual of _H. vulgaris_ that contains half digested food in +its gastral cavity is violently removed from its natural surroundings +and placed in a glass of water, the column and tentacles contract +strongly for a few minutes. The body then becomes greatly elongated and +the tentacles moderately so; the tentacles writhe in all directions +(their tips being sometimes thrust into the mouth), and the food is +ejected. + + +REPRODUCTION. + +Reproduction takes place in _Hydra_ (i) by means of buds, (ii) by means +of eggs, and (iii) occasionally by fission. + + +(a) _Sexual Reproduction._ + +The sexual organs consist of ovaries (female) and spermaries (male). +Sometimes the two kinds of organs are borne by the same individual +either simultaneously or in succession, but some individuals or races +appear to be exclusively of one sex. There is much evidence that in +unfavourable conditions the larger proportion of individuals develop +only male organs. + +In temperate climates most forms of _Hydra_ breed at the approach of +winter, but starvation undoubtedly induces a precocious sexual activity, +and the same is probably the case as regards other unfavourable +conditions such as lack of oxygen in the water and either too high or +too low a temperature. + +Downing states that in N. America (Chicago) _H. vulgaris_ breeds in +spring and sometimes as late as December; in Calcutta it has only been +found breeding in February and March. Except during the breeding-season +sexual organs are absent; they do not appear in the same position on the +column in all species. + +The spermaries take the form of small mound-shaped projections on the +surface of the column. Each consists of a mass of sperm-mother cells, in +which the spermatozoa originate in large numbers. The spermatozoa +resemble those of other animals, each possessing a head, which is shaped +like an acorn, and a long vibratile tail by means of which it moves +through the water. In the cells of the spermary the spermatozoa are +closely packed together, with their heads pointing outwards towards the +summit of the mound through which they finally make their way into the +water. The aperture is formed by their own movements. Downing (Zool. +Jahrb. (Anat.) xxi, p. 379, 1905) and other authors have studied the +origin of the spermatozoa in great detail. + +[Illustration: Fig. 28.--Eggs of _Hydra_ (magnified). + +A=egg of _H. vulgaris_ (after Chun). B=vertical section through egg of +_H. oligactis_, form A (after Brauer). C=vertical section through egg of +_H. oligactis_, form B (after Brauer).] + +The ovaries consist of rounded masses of cells lying at the base of the +ectoderm. One of these cells, the future egg, grows more rapidly than +the others, some or all of which it finally absorbs by means of lobose +pseudopodia extruded from its margin. It then makes its way by amoeboid +movements between the cells of the ectoderm until it reaches the +surface. In _H. vulgaris_ (Mem. Asiat. Soc. Beng. i, p. 350, 1906) the +egg is first visible with the aid of a lens as a minute star-shaped body +of an intense white colour lying at the base of the ectoderm cells. It +increases in size rapidly, gradually draws in its pseudopodia (the rays +of the star) and makes its way through the ectoderm to the exterior. The +process occupies not more than two hours. The issuing ovum does not +destroy the ectoderm cells as it passes out, but squeezes them together +round the aperture it makes. Owing to the pressure it exerts upon them, +they become much elongated and form a cup, in which the embryo rests on +the surface of the parent. By the time that the egg has become globular, +organic connection has ceased to exist. The embryo is held in position +partly by means of the cup of elongated ectoderm cells and partly by a +delicate film of mucus secreted by the parent. The most recent account +of the oogenesis ("ovogenesis") is by Downing (Zool. Jahrb. (Anat.) +xxvii, p. 295, 1909). + + +(b) _Budding._ + +The buds of _Hydra_ arise as hollow outgrowths from the wall of the +column, probably in a definite order and position in each species. The +tentacles are formed on the buds much as the buds themselves arise on +the column. There is much dispute as to the order in which these +structures appear on the bud, and Haacke (Jenaische Zeitschr. Naturwiss. +xiv, p. 133, 1880) has proposed to distinguish two species, _H. +trembleyi_ and _H. roeselii_, in accordance with the manner in which the +phenomenon is manifested. It seems probable, however, that the number of +tentacles that are developed in the first instance is due, at any rate +to some extent, to circumstances, for in the summer brood of _H. +vulgaris_ in Calcutta five usually appear simultaneously, while in the +winter brood of the same form four as a rule do so. Sometimes buds +remain attached to their parents sufficiently long to develop buds +themselves, so that temporary colonies of some complexity arise, but I +have not known this to occur in the case of Indian individuals. + + +(c) _Fission._ + +Reproduction by fission occurs naturally but not habitually in all +species of _Hydra_. It may take place either by a horizontal or by a +vertical division of the column. In the latter case it may be either +equal or unequal. If equal, it usually commences by an elongation in one +direction of the circumoral disk, which assumes a narrowly oval form; +the tentacles increase in number, and a notch appears at either side of +the disk and finally separates the column into two equal halves, each of +which is a complete polyp. The division sometimes commences at the base +of the column, but this is very rare. Transverse fission can be induced +artificially and is said to occur sometimes in natural conditions. It +commences by a constriction of the column which finally separates the +animal into two parts, the lower of which develops tentacles and a +mouth, while the upper part develops a basal disk. Unequal vertical +division occurs when the column is divided vertically in such a way that +the two resulting polyps are unequal in size. It is apparently not +accompanied by any great increase in the number of the tentacles, but +probably starts by one of the tentacles becoming forked and finally +splitting down the middle. + +The question of the regeneration of lost parts in _Hydra_ cannot well be +separated from that of reproduction by fission. Over a hundred and fifty +years ago Trembley found that if a polyp were cut into several pieces, +each piece produced those structures necessary to render it a perfect +polyp. He also believed that he had induced a polyp that had been turned +inside out to adapt itself to circumstances and to reverse the functions +and structure of the two cellular layers of its body. In this, however, +he was probably mistaken, for there can be little doubt that his polyp +turned right side out while not under his immediate observation. Many +investigators have repeated some of his other experiments with success +in Europe, but the Calcutta _Hydra_ is too delicate an animal to survive +vivisection and invariably dies if lacerated. It appears that, even in +favourable circumstances, for a fresh polyp to be formed by artificial +fission it is necessary for the piece to contain cells of both +cell-layers. + + +DEVELOPMENT OF THE EGG. + +The egg of _Hydra_ is said to be fertilized as it lies at the base of +the ectoderm, through which the fertilizing spermatozoon bores its way. +As soon as the egg has emerged from the cells of its parent it begins to +split up in such a manner as to form a hollow mass of comparatively +large equal cells. Smaller cells are separated off from these and soon +fill the central cavity. Before segmentation begins a delicate film of +mucus is secreted over the egg, and within this film the larger cells +secrete first a thick chitinous or horny egg-shell and within it a +delicate membrane. Development in some cases is delayed for a +considerable period, but sooner or later, by repeated division of the +cells, an oval hollow embryo is formed and escapes into the water by the +disintegration of the egg-shell and the subsequent rupture of the inner +membrane. Tentacles soon sprout out from one end of the embryo's body +and a mouth is formed; the column becomes more slender and attaches +itself by the aboral pole to some solid object. + + +ENEMIES. + +_Hydra_ seems to have few natural enemies. Martin (Q. J. Micr. Sci. +London, lii, p. 261, 1908) has, however, described how the minute worm +_Microstoma lineare_ attacks _Hydra "rubra"_ in Scottish lochs, while +the larva of a midge devours _H. vulgaris_ in considerable numbers in +Calcutta tanks (p. 156). + + +COELENTERATES OF BRACKISH WATER. + +Marine coelenterates of different orders not infrequently make their way +or are carried by the tide up the estuaries of rivers into brackish +water, and several species have been found living in isolated lagoons +and pools of which the water was distinctly salt or brackish. Among the +most remarkable instances of such isolation is the occurrence in Lake +Qurun in the Fayum of Egypt of _Cordylophora lacustris_ and of the +peculiar little hydroid recently described by Mr. C. L. Boulenger as +_Moerisia lyonsi_ (Q. J. Micr. Sci. London, lii, p. 357, pls. xxii, +xxiii, 1908). In the delta of the Ganges there are numerous ponds which +have at one time been connected with estuaries or creeks of brackish +water and have become isolated either naturally or by the hand of man +without the marine element in their fauna by any means disappearing (p. +14). The following species have been found in such ponds:-- + +(_a_) _Hydrozoa._ + +(1) _Bimeria vestita_, Wright (1859). + +Hincks, Hist. Brit. Hydr. Zooph. p. 103, pl. xv, fig. 2 (1868); +Annandale, Rec. Ind. Mus. i, p. 141, fig. 3 (1907). + +This is a European species which has also been found off S. America. It +occurs not uncommonly in the creeks that penetrate into the Ganges delta +and has been found in pools of brackish water at Port Canning. The +Indian form is perhaps sufficiently distinct to be regarded as a +subspecies. The medusoid generation is suppressed in this genus. + +(2) _Syncoryne filamentata_, Annandale (1907). + +Annandale, Rec. Ind. Mus. i, p. 139, figs. 1, 2 (1907). + +Both hydroid and medusae were found in a small pool of brackish water at +Port Canning. The specific name refers to the fact that the ends of the +rhizomes from which the polyps arise are frequently free and elongate, +for the young polyp at the tip apparently takes some time to assume its +adult form. + +(3) _Irene ceylonensis_, Browne (1905). + + Browne, in Herdman's Report on the Pearl Fisheries of + Ceylon, iv, p. 140, pl. iii, figs. 9-11 (1905); Annandale, + Rec. Ind. Mus. i, p. 142, fig. 4 (1907). + +The medusa was originally taken off the coast of Ceylon, while the +hydroid was discovered in ponds of brackish water at Port Canning. It is +almost microscopic in size. + +The first two of these species belong to the order Gymnoblastea +(Anthomedusae) and the third to the Calyptoblastea (Leptomedusae). + +(b) _Actinozoa._ + +(4) _Sagartia schilleriana_, Stoliczka (1869). + + _S. schilleriana_, Stoliczka, Journ. As. Soc. Beng. (2) + xxxviii, p. 28, pls. x, xi (1869); _Metridium + schillerianum_, Annandale, Rec. Ind. Mus. i, p. 47, pl. iii + (1907). + +This sea-anemone, which has only been found in the delta of the Ganges, +offers a most remarkable instance of what appears to be rapid adaptation +of a species to its environment. The typical form, which was described +in 1869 by Stoliczka from specimens taken in tidal creeks and estuaries +in the Gangetic area and in the ponds at Port Canning, is found attached +to solid objects by its basal disk. The race (subsp. _exul_), however, +that is now found in the same ponds has become elongate in form and has +adopted a burrowing habit, apparently owing to the fact that the bottom +of the ponds in which it lives is soft and muddy. + +In addition to these four species a minute hydroid belonging to the +order Gymnoblastea and now being described by Mr. J. Ritchie has been +taken in the ponds at Port Canning. It is a very aberrant form. + + +FRESHWATER COELENTERATES OTHER THAN HYDRA. + +_Hydra_ is the only genus of coelenterates as yet found in fresh water +in India, but several others have been discovered in other countries. +They are:-- + +(1) _Cordylophora lacustris_, Allman (1843). + + Hincks, Hist. Brit. Hydr. Zooph. p. 16, pl. iii, fig. 2 + (1868). + +This is a branching hydroid that does not produce free medusae. It forms +bushy masses somewhat resembling those formed by a luxuriant growth of +_Plumatella fruticosa_ (pl. iii, fig. 1) in general appearance. _C. +lacustris_ is abundant in canals, rivers, and estuaries in many parts of +Europe and has recently been found in the isolated salt lake +Birket-el-Qurun in the Fayum of Egypt. + +(2) _Cordylophora whiteleggei_, v. Lendenfeld (1887). + + Zool. Jahrb. ii, p. 97 (1887). + +A species or race of much feebler growth; as yet imperfectly known and +only recorded from fresh water in Australia. + +_Cordylophora_ is a normal genus of the class Hydrozoa and the order +Gymnoblastea; the next four genera are certainly Hydrozoa, but their +affinities are very doubtful. + +(3) _Microhydra ryderi_, Potts (1885). + + Potts, Q. J. Micr. Sci. London, l, p. 623, pls. xxxv, xxxvi; + Browne, _ibid._ p. 635, pl. xxxvii (1906). + +This animal, which has been found in N. America and in Germany, +possesses both an asexual hydroid and a sexual medusoid generation. The +former reproduces its species by direct budding as well as by giving +rise, also by a form of budding, to medusae that become sexually mature. +The hydroid has no tentacles. + +(4) _Limnocodium sowerbii_, Lankester (1880). + + Lankester, Q. J. Micr. Sci. London, xx, p. 351, pls. xxx, + xxxi (1880); Fowler, _ibid._ xxx, p. 507, pl. xxxii (1890). + +There is some doubt as to the different stages in the life-cycle of this +species. The medusa has been found in tanks in hot-houses in England, +France and Germany, and a minute hydroid closely resembling that of +_Microhydra ryderi_ has been associated with it provisionally. + +(5) _Limnocodium kawaii_, Oka (1907). + + Oka, Annot. Zool. Japon. vi, p. 219, pl. viii (1907). + +Only the medusa, which was taken in the R. Yang-tze-kiang, is as yet +known. + +(6) _Limnocnida tanganyikae_, Bohm (1889). + + R. T. Guenther, Ann. Nat. Hist. (6) xi, p. 269, pls. xiii, + xiv (1893). + +Only the medusa, which is found in Lake Tanganyika, Lake Victoria Nyanza +and the R. Niger, has been found and it is doubtful whether a hydroid +generation exists. + +(7) _Polypodium hydriforme_, Ussow (1885). + + Morph. Jahrb. xii, p. 137 (1887). + +Two stages in this peculiar hydroid, which is found in the R. Volga, are +known, (_a_) a spiral ribbon-like form parasitic on the eggs of the +sterlet (_Acipenser ruthenus_), and (_b_) a small _Hydra_-like form with +both filamentous and club-shaped tentacles. The life-history has not yet +been worked out[AP]. + + [Footnote AP: Since this was written, Lippen has described a + third stage in the life-history of _Polypodium_ (Zool. Anz. + Leipzig, xxxvii, Nr. 5, p. 97 (1911)).] + + +II. + +HISTORY OF THE STUDY OF HYDRA. + +Hydra was discovered by Leeuwenhoek at the beginning of the eighteenth +century and had attracted the attention of several skilful and accurate +observers before that century was half accomplished. Among them the +chief was Trembley, whose "Memoires pour servir a l'histoire d'un genre +de Polype d'eau douce"* was published at Paris 1744, and is remarkable +not only for the extent and accuracy of the observations it enshrines +but also for the beauty of its plates. Baker in his work entitled "An +attempt towards a natural history of the Polyp"* (London, 1743) and +Roesel von Rosenhof in the third part of his "Insecten-Belustigung" +(Nurenberg, 1755) also made important contributions to the study of the +physiology and structure of _Hydra_ about the same period. Linne +invented the name _Hydra_, and in his "Fauna Sueica" and in the various +editions of his "Systema Naturae" described several forms in a manner +that permits some of them to be recognized; but Linne did not +distinguish between the true _Hydra_ and other soft sessile +Coelenterates, and it is to Pallas ("Elenchus Zoophytorum," 1766) that +the credit properly belongs of reducing the genus to order. It is a +tribute to his insight that three of the four species he described are +still accepted as "good" by practically all students of the +Coelenterates, while the fourth was a form that he had not himself seen. + +In the nineteenth century the freshwater polyp became a favourite object +of biological observation and was watched and examined by a host of +observers, among the more noteworthy of whom were Kleinenberg, Nussbaum, +and Brauer, who has since the beginning of the present century made an +important contribution to the taxonomy of the genus. + + +BIBLIOGRAPHY OF HYDRA. + +_Hydra_ has been examined by thousands of students in biological +laboratories all over the civilized world, and the literature upon it is +hardly surpassed in magnitude by that on any other genus but _Homo_. The +following is a list of a few of the more important general memoirs and +of the papers that refer directly to Asiatic material. A systematic +bibliography is given by Bedot in his "Materiaux pour servir a +l'Histoire des Hydroides," Rev. Suisse Zool. xviii, fasc. 2 (1910). + +(a) _General._ + +1743. BAKER, "An attempt towards a natural history of the Polyp"* +(London). + +1744. TREMBLEY, "Memoires pour servir a l'histoire d'un genre de polypes +d'eau douce"* (Paris). + +1755. ROESEL VON ROSENHOF, "Insecten-Belustigung: iii, Hist. Polyporum." + +1766. PALLAS, "Elenchus Zoophytorum." + +1844. LAURENT, "Rech. sur l'Hydre et l'Eponge d'eau douce" ("Voy. de la +Bonite, Zoophytologie"). + +1847. JOHNSTON, "A History of the British Zoophytes" (2nd edition). + +1868. HINCKS, "History of British Hydroid Zoophytes." + +1872. KLEINENBERG, "Hydra. Eine Anatomisch Entwicklungsgeschichtliche +Untersuchung." + +1882. JICKELI, "Der Bau der Hydroidpolypen," Morph. Jahrb. viii, p. 373. + +1887. NUSSBAUM, "Ueber die Theilbarkeit der lebendigen Materie. II. +Mittheilung. Beitraege zur Naturgeschichte des Genus Hydra," Arch. mikr. +Anat. Bonn, xxix, p. 265. + +1891. BRAUER, "Ueber die Entwicklung von Hydra," Zeitschr. wiss. Zool. +Leipzig, lii, p. 169. + +1892. CHUN, "Coelenterata (Hohlthiere)," in Bronn's Thier-Reichs II (2). + +1905. DOWNING, "The spermatogenesis of Hydra," Zool. Jahrb. (Anat.) xxi, +p. 379. + +1908. BRAUER, "Die Benennung und Unterscheidung der Hydra-Arten," Zool. +Ann. xxxiii, p. 790. + +1909. FRISCHHOLZ, "Biologie und Systematik im Genus Hydra," Braun's +Annal. Zool. (Wuerzburg) iii, p. 105. + +1910. BERNINGER, "Ueber Einwirkung des Hungers auf Hydra," Zool. Anz. +xxxvi, p. 271. + +(b) _Asiatic References._ + +1894. RICHARD, "Sur quelques Animaux inferieurs des eaux douces du +Tonkin (Protozoaires, Rotiferes, Entomostraces)," Mem. Soc. zool. +France, vii, p. 237. + +1904. VON DADAY, "Mikroskopische Suesswasserthiere aus Turkestan," Zool. +Jahrb. (Syst.) xix, p. 469. + +1906. ANNANDALE, "Notes on the Freshwater Fauna of India. No. IV. _Hydra +orientalis_ and its bionomical relations with other Invertebrates," J. +Asiat. Soc. Bengal (new series), ii, p. 109. + +1906. ANNANDALE, "The Common _Hydra_ of Bengal: its Systematic Position +and Life History," Mem. As. Soc. Bengal, i, p. 339. + +1907. ANNANDALE, "Notes on the Freshwater Fauna of India. No. X. _Hydra +orientalis_ during the Rains," J. Asiat. Soc. Bengal (new series), iii, +p. 27. + +1907. ANNANDALE, "Notes on the Freshwater Fauna of India. No. XI. +Preliminary Note on the occurrence of a Medusa (_Irene ceylonensis_, +Browne) in a brackish pool in the Ganges Delta and on the Hydroid Stage +of the species," J. Asiat. Soc. Bengal (new series), iii, p. 79. + +1907. WILLEY, "Freshwater Sponge and Hydra in Ceylon," Spolia Zeylan. +Colombo, iv, p. 184. + +1908. ANNANDALE, "Observations on specimens of _Hydra_ from Tibet, with +notes on the distribution of the genus in Asia," Rec. Ind. Mus. ii, p. +311. + +1910. POWELL, "Lessons in Practical Biology for Indian Students" +(Bombay). + +1910. LLOYD, "An Introduction to Biology for Students in India" +(London). + + + + +GLOSSARY OF TECHNICAL TERMS USED IN PART II. + + + _Aboral_ (or _basal_) The disk by means of which a free polyp + _disk_ attaches itself to external objects. + + _Cnidoblast_ The living cell of the nematocyst or + nettle-cell (_q. v._). + + _Cnidocil_ A minute bristle that projects on the + surface in connection with a nettle-cell + (_q. v._). + + _Column_ The upright or potentially upright + part of a polyp (_q. v._). + + _Ectoderm_ The external cell-layer of the body-wall. + + _Endoderm_ The internal cell-layer of the body-wall. + + _Green (chlorophyll) Minute green bodies contained in cells + corpuscles_ of polyps or other animals and + representing a stage in the life-history + of an alga (_Chlorella_). + + _Mesogloea_ The intermediate, gelatinous layer of + the body-wall. + + _Nettle-cell (nematocyst)_ A cell capsule full of liquid in which + an eversible thread is coiled up. + + _Oral disk_ The eminence that surrounds the mouth + and is surrounded by tentacles. + + _Peristome_ See "oral disk." + + _Polyp_ An individual coelenterate of simple + structure that is fixed temporarily or + permanently by one end of a more + or less cylindrical body and possesses + a mouth at the other end. + + _Tentacles_ Filamentous outgrowths (in _Hydra_ + hollow) of the body-wall round the + mouth. + + + + + LIST OF THE INDIAN HYDRIDA. + + + Class HYDROZOA. + + Order ELEUTHEROBLASTEA. + + Family HYDRIDAE. + + Genus HYDRA, _Linne_ (1746). + + 24. _H. vulgaris_, Pallas (1766). + + 25. _H. oligactis_, Pallas (1766). + + +Order ELEUTHEROBLASTEA. + +Naked hydrozoa which reproduce their kind by means of buds or eggs, or +by fission, without exhibiting the phenomena of alternation of +generations. + + +Family HYDRIDAE. + + HYDRAIDAE, Johnston, Hist. Brit. Zooph. (ed. 2) i, p. 120 + (1847). + HYDRIDAE, Hincks, Hist. Brit. Hydroid. Zooph. p. 309 (1868). + +Small Eleutheroblastea in which the mouth is surrounded by hollow +tentacles. Permanent colonies are not formed, but reproduction by +budding commonly takes place. + + +Genus HYDRA, _Linne_. + +TYPE, _Hydra viridis_, Linne. + +Freshwater polyps which produce eggs with hard chitinous shells. +Although habitually anchored by the end of the body furthest from the +mouth to extraneous objects, they possess considerable powers of +locomotion. They are extremely contractile and change greatly from time +to time in both form and size. + +Only three well-established species of the genus, which is universally +distributed and occurs only in fresh or brackish[AQ] water, can be +recognized, namely, _H. viridis_, Linne (=_H. viridissima_, Pallas), _H. +vulgaris_, Pallas (=_H. grisea_, Linne), and _H. oligactis_, Pallas +(=_H. fusca_, Linne). The two latter occur in India, but _H. viridis_ +does not appear to have been found as yet anywhere in the Oriental +Region, although it is common all over Europe and N. America and also in +Japan. The distribution of _H. vulgaris_ is probably cosmopolitan, but +there is some evidence that _H. oligactis_ avoids tropical districts, +although, under the name _Hydra fusca_, it has been doubtfully recorded +as occurring in Tonquin[AR]. + + [Footnote AQ: A small form of _H. viridis_ (var. _bakeri_, + Marshall) is found in brackish water in England.] + + [Footnote AR: Richard, Mem. Soc. zool. France, vii, p. 237 + (1894).] + +The three species may be distinguished from one another by the following +key:-- + + [I. Colour leaf-green; the cells contain green + (chlorophyll) corpuscles of definite form. + A. Tentacles comparatively stout, habitually + shorter than the column, which is cylindrical. + Egg-shell without spines, ornamented + with a reticulate pattern _viridis_.] + II. Colour never leaf-green; no chlorophyll + corpuscles present in the cells. + A. Tentacles capable of great elongation but + when the animal is at rest never very much + longer than the column, which is cylindrical + when the gastral cavity is empty. + Largest nettle-cells almost as broad as + long. Egg-shell bearing long spines most + of which are divided at the tips _vulgaris_, p. 148. + B. Tentacles, even when the animal is at rest, + much longer than the column, the basal + part of which, even when the gastral + cavity is empty, is constricted. Largest + nettle-cells considerably longer than + broad. Egg-shell smooth or bearing + short, simple spines _oligactis_, p. 158. + + +24. Hydra vulgaris, _Pallas_. + + Polypes de la seconde espece, Trembley, Mem. pour servir a + l'histoire d'un genre de polypes d'eau douce*, pl. i, figs. + 2, 5; pl. vi, figs. 2, 8; pl. viii, figs. 1-7; pl. xi, figs. + 11-13 (1744). + + Roesel von Rosenhof, Insecten-Belustigung, iii, Hist. + Polyporum, pls. lxxvi, lxxvii, lxxix-lxxxiii (1755). + + ? _Hydra polypus_, Linne, Fauna Suecica, p. 542 (1761). + + _Hydra vulgaris_, Pallas, Elenchus Zoophytorum, p. 30 + (1766). + + ? _Hydra attenuata_, _id_., _ibid_. p. 32. + + _Hydra grisea_, Linne (Gmelin), Systema Naturae (ed. 13), p. + 3870 (1782). + + _Hydra pallens_, _id_., _ibid_. p. 3871. + + _Hydra vulgaris_, Ehrenberg, Abhandl. Akad. Wiss. Berlin, + 1836, p. 134, taf. ii. + + _Hydra brunnea_, Templeton, London's Mag. Nat. Hist. ix, p. + 417 (1836). + + _Hydra vulgaris_, Laurent, Rech. sur l'Hydre at l'Eponge + d'eau douce (Voy. de la Bonite, Zoophytologie), p. 11, pl. + i, pl. ii, figs. 2, 2'' (1844). + + _Hydra vulgaris_, Johnston, Hist. British Zoophytes (ed. 2), + i, p. 122, pl. xxix, fig. 2 (1847). + + _Hydra vulgaris_, Hincks, Hist. British Hydroid Zoophytes, + i, p. 314, fig. 41 (1868). + + _Hydra aurantiaca_, Kleinenberg, Hydra, p. 70, pl. i, fig. + 1, pl. iii, fig. 10 (1872). + + _Hydra trembleyi_, Haacke, Zool. Anz. Leipzig, ii, p. 622 + (1879). + + _Hydra grisea_, Jickeli, Morph. Jahrb. viii, p. 391, pl. + xviii, fig. 2 (1883). + + _Hydra grisea_, Nussbaum, Arch. mikr. Anat. Bonn, xxix, p. + 272, pl. xiii, pl. xiv, figs. 33, 37, 47 (1887). + + ? _Hydra hexactinella_, v. Lendenfeld, Zool. Jahrb. Jena, + ii, p. 96, pl. vi, figs. 13, 14 (1887). + + ? _Hydra hexactinella_, _id_., Proc. Linn. Soc. N. S. Wales, + x, p. 678, p. xlviii, figs. 1-4 (1887). + + _Hydra grisea_, Brauer, Zeit. wiss. Zool. Leipzig, lii, p. + 169 (1891). + + _Hydra grisea_, Chun, in Broenn's Thier-Reichs, ii (2), pl. + ii, figs. 2_b_, 2_c_, 5 (1892). + + _Hydra grisea_, Downing, Zool. Jahrb. (Anat.) Jena, xxi, p. + 381 (1905). + + _Hydra orientalis_, Annandale, J. Asiat. Soc. Bengal, (new + series) i, 1905, p. 72. + + _Hydra orientalis_, _id._, _ibid._ (new series) ii, 1906, p. + 109. + + _Hydra orientalis_, _id._, Mem. Asiat. Soc. Bengal, i, p. + 340 (1906). + + ? _Hydra orientalis_, Willey, Spol. Zeylan. Colombo, iv, p. + 185 (1907). + + _Hydra grisea_, Weltner, Arch. Naturg. Berlin, lxxiii, i, p. + 475 (1907). + + _Hydra vulgaris_, Brauer, Zool. Anz. xxxiii, p. 792, fig. 1 + (1908). + + _Hydra orientalis_, Annandale, Rec. Ind. Mus. ii, p. 312 + (1908). + + _Hydra grisea_, Frischholz, Braun's Zool. Annal. (Wuerzburg), + iii, pp. 107, 134, &c., figs. 1 and 10-17 (1909). + + _Hydra grisea_, _id._, Biol. Centralbl. Berlin, xxix, p. 184 + (1909). + + _Hydra vulgaris_, Brauer, Die Suesswasserfauna Deutschlands, + xix, p. 192, figs. 336-338 (1909). + + _Hydra pentactinella_, Powell, Lessons in Practical Biology + for Indian Students, p. 24 (Bombay, 1910). + + +Phase _orientalis*_, Annandale. + +_Colour_ variable; in summer usually pale, in winter either deep orange, +dull brown, or dark green. The cells do not contain spherical or oval +coloured bodies. + +[Illustration: Fig. 29.--_Hydra vulgaris_, from Calcutta (phase +_orientalis_). + +A=winter brood; B=summer brood, the same individual in an expanded and a +contracted condition. B is more highly magnified than A.] + +_Column_ slender and capable of great elongation, normally almost +cylindrical, but when containing food often shaped like a wine-glass. +The surface is thickly set with nettle-cells the cnidocils of which give +it an almost hirsute appearance under the microscope. When extended to +the utmost the column is sometimes nearly 30 mm. (1-1/5 inches) long, +but more commonly it is about half that length or even shorter. + +_Tentacles_ usually 4-6, occasionally 8. They are always slender except +when they are contracted, then becoming swollen at the base and slightly +globular at the tip. If the animal is at rest they are not very much +longer than the body, but if it is hungry or about to move from one +place to another they are capable of very great extension, often +becoming like a string of minute beads (the groups of nettle-cells) +strung on an invisible wire. + +_Nettle-cells._ The capsules with barbed threads (fig. 27, p. 131) are +very variable in size, but they are invariably broad in proportion to +their length and as a rule nearly spherical. In a _Hydra_ taken in +Calcutta during the winter the largest capsules measured (unexploded) +0.0189 mm. in breadth and 0.019 in length, but in summer they are +smaller (about 0.012 mm. in breadth). Smaller capsules with barbed +threads always occur. The barbed threads are very long and slender. At +their base they bear a circle of stout and prominent spines, usually 4 +in number; above these there are a number of very small spines, but the +small spines are usually obscure. Malformed corpuscles are common. The +capsules with unbarbed threads are very nearly as broad at the distal as +at the proximal end; they are broadly oval with rounded ends. + +_Reproductive organs._ The reproductive organs are confined to the upper +part of the body. In India eggs (fig. 28, p. 137) are seldom produced. +They sometimes appear, however, at the beginning of the hot weather. In +form they are spherical, and their shell bears relatively long spines, +which are expanded, flattened and more or less divided at the tip. The +part of the egg that is in contact with the parent-polyp is bare. +Spermaries are produced more readily than ovaries; they are mammillate +in form and number from 4 to 24. Ovaries and spermaries have not been +found on the same individual. + +_Buds_ are confined to a narrow zone nearer the base than the apex of +the column. Rarely more than 2 are produced at a time, and I have never +seen an attached bud budding. In winter 5 tentacles are as a rule +produced simultaneously, and in summer 4. In the former case a fifth +often makes its appearance before the bud is liberated. + +In Calcutta two broods can be distinguished, a cold-weather brood, which +is larger, stouter, and more deeply coloured, produces buds more freely, +has larger nematocysts, and as a rule possesses 6 tentacles; and a +hot-weather brood, which is smaller, more slender and paler, produces +buds very sparingly, has smaller nematocysts, and as a rule possesses +only 4 or 5 tentacles. Only the cold-weather form is known to become +sexually mature. There is evidence, however, that in those parts of +India which enjoy a more uniform tropical climate than Lower Bengal, +polyps found at all times of year resemble those found in the hot +weather in Calcutta, and sometimes produce spermatozoa or eggs. + +I have recently had an opportunity of comparing specimens of the +Calcutta hot-weather form with well-preserved examples of _H. vulgaris_, +Pallas (=_H. grisea_, Linn.), from England. They differ from these +polyps in very much the same way as, but to a greater degree than they +do from the winter phase of their own race, and I have therefore no +doubt that _H. orientalis_ is merely a tropical phase of Pallas's +species. My description is based on Indian specimens, which seem to +differ, so far as anatomy is concerned, from European ones in the +following points:-- + + (1) The sexes are invariably distinct; + (2) the nematocysts are invariably smaller. + +I have seen in Burma an abnormal individual with no tentacles. Its buds, +however, possessed these organs. + +TYPE. None of the older types of _Hydra_ are now in existence. That of +_H. orientalis_ is, however, in the collection of the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--_H. vulgaris_ is common in Europe and N. +America and is probably found all over tropical Asia. The following are +Indian and Ceylon localities:--BENGAL, Calcutta and neighbourhood +(_Annandale_, _Lloyd_); Adra, Manbhum district (_Paiva_), Rampur Bhulia +on the R. Ganges (_Annandale_); Chakradharpur, Chota Nagpur +(_Annandale_); Pusa, Bihar (_Annandale_); Puri, Orissa (_Annandale_): +MADRAS, sea-beach near Madras town (_Henderson_): BOMBAY, island of +Bombay (_Powell_): BURMA, Mandalay, Upper Burma, and Moulmein, N. +Tenasserim (_Annandale_): CEYLON, Colombo and Peradeniya (_Willey_, +_Green_). Dr. A. D. Imms tells me that he has obtained specimens that +probably belong to this species in the Jumna at Allahabad. + +BIOLOGY.--In India _H. vulgaris_ is usually found, so far as my +experience goes, in stagnant water. In Calcutta it is most abundant in +ponds containing plenty of aquatic vegetation, and seems to be +especially partial to the plant _Limnanthemum_, which has floating +leaves attached to thin stalks that spring up from the bottom, and to +_Lemna_ (duckweed). Dr. Henderson, however, found specimens in a pool of +rain-water on the sea-shore near Madras. + +There is evidence that each of the two broods which occur in Lower +Bengal represents at least one generation; probably it represents more +than one, for tentacles are rarely if ever produced after the animal has +obtained its full size, and never (or only owing to accident) decrease +in number after they have once appeared. The winter form is found +chiefly near the surface of the water, especially on the roots of +duckweed and on the lower surface of the leaves of _Limnanthemum_; but +the summer form affects deeper water in shady places, and as a rule +attaches itself to wholly submerged plants. The latter form is to be met +with between March and October, the cold-weather form between October +and March, both being sometimes found together at the periods of +transition. In the unnatural environment of an aquarium, however, +individuals of the winter form lose their colour and become attenuated, +in these features resembling the summer form, even in the cooler months. +Buds produced in these conditions rarely have more than five tentacles +or themselves produce buds freely after liberation. + +The buds appear in a fixed order and position, at any rate on +individuals examined in winter; in specimens of the summer form the +position is fixed, but the order is irregular. Each quadrant of the +column has apparently the power of producing, in a definite zone nearer +the aboral pole than the mouth, a single bud; but the buds of the +different quadrants are not produced simultaneously. If we imagine that +the quadrants face north, south, east, and west, and that the first bud +is produced in the north quadrant, the second will be produced in the +east quadrant, the third in the south, and the fourth in the west. It is +doubtful whether more than four buds are produced in the lifetime of an +individual, and apparently attached buds never bud in this race. The +second bud usually appears before the first is liberated, and this is +also the case occasionally as regards the third, but it is exceptional +for four buds to be present at one time. About three weeks usually +elapse between the date at which the bud first appears as a minute +conical projection on the surface of the parent and that at which it +liberates itself. This it does by bending down, fixing itself to some +solid object by means of the tips of its tentacles, the gland-cells of +which secrete a gummy fluid, and then tearing itself free. + +Although it is rare for more than two buds to be produced +simultaneously, budding is apparently a more usual form of reproduction +than sexual reproduction. Individuals that bear eggs have not yet been +found in India in natural conditions, although males with functional +spermaries are not uncommon at the approach of the hot weather. The few +eggs that I have seen were produced in my aquarium towards the end of +the cold weather. Starvation, lack of oxygen, and too high a temperature +(perhaps also lack of light) appear to stimulate the growth of the male +organs in ordinary cases, but perhaps they induce the development of +ovaries in the case of individuals that are unusually well nourished. + +The spines that cover the egg retain debris of various kinds upon its +surface, so that it becomes more or less completely concealed by a +covering of fragments of dead leaves and the like even before it is +separated from the polyp. Its separation is brought about by its falling +off the column of the parent. Nothing is known of its subsequent fate, +but probably it lies dormant in the mud through the hot weather. Eggs +are sometimes produced that have no shells. This is probably due to the +fact that they have not been fertilized. + +Reproduction by fission occurs rarely in the Indian _Hydra_, but both +equal and unequal vertical fission have been observed. In the case of +equal fission the circumoral area lengthens in a horizontal direction, +and as many extra tentacles as those the polyp already possesses make +their appearance. The mouth then becomes constricted in the middle and +notches corresponding to its constriction appear at either side of the +upper part of the column. Finally the whole animal divides into two +equal halves in a vertical direction. I have only seen one instance of +what appeared to be unequal vertical fission--that of a polyp consisting +of two individuals still joined together by the basal disk, but one +about half the size of the other. Each had three well-developed +tentacles, and in addition a minute fourth tentacle. This was situated +on the side opposed to that of the other individual which bore a similar +tentacle. Transverse fission has not been observed. The Indian _Hydra_ +is a very delicate animal as compared with such a form as _H. viridis_, +and all attempts to produce artificial fission without killing the polyp +have as yet failed. + +Young individuals are often, and adults occasionally, found floating +free in the water, either with the mouth uppermost and the tentacles +extended so as to cover as large an area as possible or with the aboral +pole at the surface. In the former case they float in mid-water, being +of nearly the same specific gravity as the water, and are carried about +by any movement set up in it. In the latter case, however, the base of +the column is actually attached to some small object such as the cast +skin of a water-flea or to a minute drop of mucus originally given out +by the polyp's own mouth; the tentacles either hang downwards or are +spread out round the mouth, and the animal is carried about by wind or +other agencies acting on the surface. + +In addition to this passive method of progression the polyp can crawl +with considerable rapidity. In doing so it bends its column down to the +object along which it is about to move in such a way that it lies almost +parallel to the surface, the basal disk, however, being still attached. +The tentacles are then extended and attach themselves near the tips to +the surface a considerable distance away. Attachment is effected by the +secretion of minute drops of adhesive substance from gland-cells. The +basal disk is liberated and the tentacles contract, dragging the column, +which still lies prone, along as they do so. The basal disk again +affixes itself, the tentacles wrench themselves free, the surface of +their cells being often drawn out in the process into pseudopodia-like +projections, which of course are not true pseudopodia[AS] but merely +projections produced by the mechanical strain. The whole action is then +repeated. The polyp can also pull itself across a space such as that +between two stems or leaves by stretching out one of its tentacles, +fixing the tip to the object it desires to reach, pulling itself free +from its former point of attachment, and dragging itself across by +contracting the fixed tentacle. The basal disk is then turned round and +fixed to the new support. + + [Footnote AS: See Zykoff, Biol. Centralbl. xviii, p. 272 + (1898), and Annandale, Rec. Ind. Mus. i, p. 67 (1907).] + +The Indian polyp, like all its congeners, is attracted by light, but it +is more strongly repelled by heat. Probably it never moves in a straight +line, but if direct sunlight falls on one side of a glass aquarium, the +polyps move away from that side in a much less erratic course than is +usually the case. If conditions are favourable, they often remain in one +spot for weeks at a time, their buds congregating round them as they are +set free. In a natural environment it seems that regular migrations take +place in accordance with changes in temperature, for whereas in cool +weather many individuals are found adhering to the lower surface of the +floating leaves of _Limnanthemum_, few are found in this position +immediately after a rise in the thermometer. If the rise is only a small +one, they merely crawl down the stems to the end of which the leaves are +attached, but as soon as the hot weather begins in earnest, the few that +survive make their way to the deepest and most shady part of the pond. +In captivity the polyps seek the bottom of any vessel in which they are +contained, if sunlight falls on the surface of the water. + +The chief function of the tentacles is that of capturing prey. The +Indian polyp feeds as a rule in the early morning, before the day has +become hot. In an aquarium at any rate, the tentacles are never more +than moderately extended during the night. If the polyp is hungry, they +are extended to their greatest length in the early morning, and if prey +is not captured, they sometimes remain in this condition throughout the +day. In these circumstances they hang down or stand up in the water +closely parallel to one another, and often curved in the middle as if a +current were directed against them. Prey that comes in contact with one +of them has little chance of escape, for nematocysts from all the +tentacles can be readily discharged against it. Approximately once in +half an hour the direction of the tentacles is changed, but I have been +unable to observe any regular rhythmical movements of the tentacles or +any correlation between those of a parent polyp and the buds still +attached to it. + +The prey consists chiefly of the young larvae of midges (Chironomidae) and +may-flies, but small copepod and phyllopod crustacea are also captured. + +As soon as the prey adheres firmly to the tentacles and has become +paralysed it is brought to the mouth by their contracting strongly and +is involved in a mass of colourless mucus extruded from the digestive +cavity. Partly by the contraction of muscle-fibres in the body-wall and +partly by movements of the mouth itself assisted by the mucus, which +apparently remains attached to the walls of the cavity, the food is +brought into the mouth. If it is at all bulky, it remains in the upper +part of the cavity, the gland-cells pouring out a digestive fluid upon +it and so dissolving out soluble substances. A large share of the +substances thus prepared falls down to the bottom of the cavity and are +there digested by the endoderm cells. The insoluble parts of the food +are, however, ejected from the mouth without ever reaching the base of +the cavity. + +The colour of the polyp appears to be due mainly to the results of +digestion. Brown or orange individuals recently captured in a pond and +kept in favourable conditions take three or four days to digest their +food, and the excreta ejected from the mouth then take the form of a +white flocculent mass. If, however, the same individuals are kept for +long in a glass aquarium, they lose their colour, even though they feed +readily. Digestion is then a much more rapid process, and the excreta +contain minute, irregular, coloured granules, which appear to be +identical with those contained in the endoderm cells of individuals that +have recently digested a meal fully. Starved individuals are always +nearly colourless. It seems, therefore, that in this species colour is +due directly to the products of digestion, and that digestion does not +take place so fully in unfavourable conditions or at a high temperature +as it does in more healthy circumstances. The dark green colour of some +polyps is, however, less easily explained. I have noticed that all the +individuals which have produced eggs in my aquarium have been of this +colour, which they have retained in spite of captivity; whereas +individuals that produced spermatozoa often lost their colour completely +before doing so, sometimes becoming of a milky white owing to the +accumulation of minute drops of liquid in their endoderm cells. Even in +green individuals there is never any trace in the cells of coloured +bodies of a definite form. + +The Indian polyp, unlike European representatives of its species, is a +very delicate little animal. In captivity at any rate, three +circumstances are most inimical to its life: firstly, a sudden rise in +the temperature, which may either kill the polyp directly or cause it to +hasten its decease by becoming sexually mature; secondly, the lack of a +free current of air on the surface of the aquarium; and thirdly, the +growth of a bacterium, which forms a scum on the top of the water and +clogs up the interstices between the leaves and stems of the +water-plants, soon killing them. If adult polyps are kept even in a +shallow opaque vessel which is shut up in a room with closed shutters +they generally die in a single night; indeed, they rarely survive for +more than a few days unless the vessel is placed in such a position that +air is moving almost continuously over its surface. The bacterium to +which I allude often almost seals up the aquarium, especially in March +and April, in which months its growth is very rapid. Strands of slime +produced by it surround the polyp and even enter its mouth. In this +event the polyp retracts its tentacles until they become mere +prominences on its disk, and shrinks greatly in size. The colouring +matter in its body becomes broken up into irregular patches owing to +degeneracy of the endoderm cells, and it dies within a few hours. + +_Hydra_ in Calcutta is often devoured by the larva of a small midge +(_Chironomus fasciatipennis_, Kieffer) common in the tanks from November +to February. In the early stages of its larval life this insect wanders +free among communities of protozoa (_Vorticella_, _Epistylis_, &c.) and +rotifers on which it feeds, but as maturity approaches begins to build +for itself a temporary shelter of one of two kinds, either a delicate +silken tunnel the base of which is formed by some smooth natural +surface, or a regular tube the base of which is fixed by a stalk +situated near the middle of its length to some solid object, while the +whole surface is covered with little projections. The nature of the +covering appears to depend partly on that of the food-supply and partly +on whether the larva is about to change its skin. + +I had frequently noticed that tunnels brought from the tank on the under +surface of _Limnanthemum_ leaves had a _Hydra_ fixed to them. This +occurred in about a third of the occupied shelters examined. The _Hydra_ +was always in a contracted condition and often more or less mutilated. +By keeping a larva together with a free polyp in a glass of clean water, +I have been able to observe the manner in which the polyp is captured +and entangled. The larva settles down near the base of its column and +commences to spin a tunnel. When this is partially completed, it passes +a thread round the polyp's body to which it gives a sharp bite. This +causes the polyp to bend down its tentacles, which the larva entangles +with threads of silk, doing so by means of rapid, darting movements; for +the nettle-cells would prove fatal should they be shot out against its +body, which is soft. Its head is probably too thickly coated with chitin +to excite their discharge. Indeed, small larvae of this very species form +no inconsiderable part of the food of the polyp, and, so far as my +observations go, a larva is always attacked in the body and swallowed in +a doubled-up position. + +When the _Hydra_ has been firmly built into the wall of the shelters and +its tentacles fastened down by their bases on the roof, the larva +proceeds, sometimes after an interval of some hours, to eat the body, +which it does very rapidly, leaving the tentacles attached to its +shelter. The meal only lasts for a few minutes; after it the larva +enjoys several hours' repose, protected by remains of its victim, which +retain a kind of vitality for some time. During this period it remains +still, except for certain undulatory movements of the posterior part of +the body which probably aid in respiration. Then it leaves the shelter +and goes in search of further prey. Its food, even when living in a +tunnel, does not consist entirely of _Hydra_. I have watched a larva +building its shelter near a number of rotifers, some of which it +devoured and some of which it plastered on to its tunnel. + +The tubular shelters occasionally found are very much stouter structures +than the tunnels, but are apparently made fundamentally of the same +materials; and structures intermediate between them and the tunnels are +sometimes produced. The larva as a rule fastens to them branches +detached from living colonies of Vorticellid protozoa such as +_Epistylis_[AT]. + + [Footnote AT: Further particulars regarding the life-history + of this larva will be found on pp. 114 and 115, J. Asiat. + Soc. Bengal, ii (n. s.) 1906.] + +Of animals living in more or less intimate relations with the polyp, I +have found two very distinct species of protozoa, neither of which is +identical with either of the two commonly found in association with +_Hydra_ in Europe, _Trichodina pediculus_ and _Kerona polyporum_. On two +occasions, one in January and the other at the beginning of February, I +have seen a minute colourless flagellate on the tentacles of the +Calcutta polyp. On the first occasion the tentacles were completely +covered with this protozoon, so that they appeared at first sight as +though encased in flagellated epithelium. The minute organism was +colourless, transparent, considerably larger than the spermatozoa of +_Hydra_, slightly constricted in the middle and rounded at each end. It +bore a long flagellum at the end furthest from its point of attachment, +the method of which I could not ascertain. When separated from the polyp +little groups clung together in rosettes and gyrated in the water. On +the other occasion only a few individuals were observed. Possibly this +flagellate was a parasite rather than a commensal, as the individual on +which it swarmed was unusually emaciated and colourless, and bore +neither gonads nor buds. The larger stinging cells were completely +covered by groups of the organism, and possibly this may have interfered +with the discharge of stinging threads. + +The other protozoon was _Vorticella monilata_, Tatem, which has been +found, not in association with _Hydra_, in Europe and S. America. In +Calcutta I have only seen it attached to the column of the polyp, but +probably it would also be found, if carefully looked for, attached to +water-weeds. + +Especially in the four-rayed stage, the polyp not infrequently attaches +itself to shells of _Vivipara_, and, more rarely, to those of other +molluscs. It is doubtful whether this temporary association between +_Hydra_ and the mollusc is of any importance to the latter. Even when +the polyp settles on its body and not on its shell (as is sometimes the +case) the _Vivipara_ appears to suffer no inconvenience, and makes no +attempt to get rid of its burden. It is possible, on the other hand, +that the _Hydra_ may protect it by devouring would-be parasites; but of +this there is no evidence[AU]. + + [Footnote AU: In the Calcutta tanks operculate molluscs such + as _Vivipara_ are certainly more free from visible attack + than non-operculate species. This is the case for instance, + as regards the common aquatic glowworm (_Luciola_ sp.), + which destroys large numbers of individuals of _Limnophysa_, + _Limnaeus_, &c. If it has been starved for several days in an + aquarium it will attack an operculate form, but rarely with + success. Similarly _Chaetogaster bengalensis_ attaches itself + exclusively to non-operculate forms. In the one case the + polyp could do very little against an adversary with so + stout an integument as the insect, while, in the other, it + is doubtful whether the worm does any harm to its host. The + polyp would afford very little protection against the + snail's vertebrate enemies or against what appears to be its + chief foe, namely, drought. As the water sinks in the tank + non-operculate species migrate to the deeper parts, but + _Vivipara_ and _Ampullaria_ close their shells, remain where + they are, and so often perish, being left high and dry, + exposed to the heat of the sun.] + +The association, however, is undoubtedly useful to _Hydra_. The mud on +the shells of _Vivipara_ taken on floating objects shows that in cool +weather the snail comes up from the bottom to the surface, and it +probably goes in the opposite direction in hot weather. Moreover, the +common Calcutta species (_V. bengalensis_) feeds very largely, if not +exclusively, on minute green algae. It therefore naturally moves towards +spots where smaller forms of animal and vegetable life abound and +conditions are favourable for the polyp. The polyp's means of +progression are limited, and the use of a beast of burden is most +advantageous to it, for it can detach itself when it arrives at a +favourable habitat. If specimens are kept in water which is allowed to +become foul, a very large proportion of them will attach themselves to +any snails confined with them. Under natural conditions they would thus +in all probability be rapidly conveyed to a more suitable environment. +In the tanks it is far commoner to find young four-rayed polyps on +_Vivipara_ than individuals with five or six rays; but the adults of the +species are far less prone to change their position than are the young. + +The Calcutta _Hydra_, especially in spring, exhibits a distinct tendency +to frequent the neighbourhood of sponges and polyzoa, such as _Spongilla +carteri_ and the denser forms of _Plumatella_. Possibly this is owing to +the shade these organisms provide. + + +25. Hydra oligactis, _Pallas_. + + Polypes de la troisieme espece, Trembley, Mem. hist. + Polypes,* pl. i, figs. 3, 4, 6; pl. ii, figs. 1-4; pl. iii, + fig. 11; pl. v, figs. 1-4; pl. vi, figs. 3-7, 9, 10; pl. + viii, figs. 8, 11; pl. ix (1744). + + Roesel von Rosenhof, Insekt.-Belustigung, iii, Hist. Polyp., + pls. lxxxiv-lxxxvi (1755). + + _Hydra socialis_, Linne, Fauna Sueica, p. 542 (1761). + + _Hydra oligactis_, Pallas, Elench. Zooph. p. 29 (1766). + + ? _Hydra attenuata_, _id._, _ibid._ p. 32. + + _Hydra fusca_, Linne, Syst. Nat. (ed. 13), p. 3870 (1782). + + _Hydra oligactis_, Johnston, Brit. Zooph. i, p. 124, fig. 27 + (p. 120) (1847). + + _Hydra oligactis_, Hincks, Hist. Brit. Hydr. Zooph. i, p. + 315, fig. 42 (1868). + + _Hydra roeselii_, Haacke, Jena Zeitschr. Naturwiss. xiv, p. + 135 (1880). + + ? _Hydra rhaetica_, Asper, Zool. Anz. 1880, p. 204, figs. + 1-3. + + _Hydra vulgaris_, Jickeli (_nec_ Pallas), Morph. Jahrb. + viii, p. 391, pl. xviii, fig. 3 (1882). + + _Hydra fusca_, Nussbaum, Arch. mikr. Anat. Bonn, xxix, p. + 273, pl. xiv, figs. 34-36, pl. xv, figs. 48-51, &c. (1887). + + _Hydra fusca_, Brauer, Zeit. wiss. Zool. Leipzig, lii, p. + 177, pl. xi, figs. 2, 5, 6; pl. xii, fig. 6 (1891). + + _Hydra_ sp. ? _id._, _ibid._ pl. xi, figs. 3, 3a, 4, 7, 8; + pl. xii, figs. 1, 2, 5-13. + + _Hydra fusca_, Chun in Broenn's Thier-Reichs, ii (2), pl. ii, + figs. 2(_a_), 4, 6 (1892). + + _Hydra monoecia_, Downing, Science* (5) xii, p. 228. + + _Hydra fusca_, _id._, Zool. Jahrb. (Anat.) xxi, p. 382 + (1905). + + _Hydra dioecia_, _id._, _ibid._ pl. xxiii, figs. 6, 7, &c. + + _Hydra fusca_, Hertwig, Biol. Centralbl. xxvi, p. 489 + (1906). + + _Hydra oligactis_, Brauer, Zool. Anz. xxxiii, p. 792, fig. 2 + (1908). + + _Hydra polypus_, _id._, _ibid._ + + _Hydra fusca_, Frischholz, Ann. Zool. (Wuerzburg), iii, p. + 114, figs. 2-9 (1909). + + _Hydra oligactis_, Brauer, Suesswasserfauna Deutschl. xix, p. + 193, figs. 339-341 (1909). + + _Hydra polypus_, _id._, _ibid._ figs. 342-344. + +This species differs from _H. vulgaris_ in the following characters:-- + + (1) Even when the gastral cavity is empty, the basal part of + the column is distinctly more slender than the upper part; + (2) even when the animal is at rest, the tentacles are much + longer than the column; + (3) the nettle-cells of both types are usually smaller and + more uniform in size than in the other species; those with + barbed threads (fig. 27, p. 131) are always flask-shaped and + somewhat narrower in proportion to their length, while those + with simple threads are pointed or almost pointed at their + distal end; + (4) the stinging threads of the more complex form are + comparatively stout and short; + (5) there are comparatively few nettle-cells in the column; + (6) the egg-shell is nearly smooth or covered more or less + completely with short, simple spines (fig. 28, p. 137). + +_H. oligactis_ is usually a more vigorous form than _H. vulgaris_ and, +in spite of its name, has often a considerable number of tentacles. The +few Indian specimens examined have, however, been small and have not had +more than six tentacles. I have not seen an Indian specimen with more +than two buds, but European specimens sometimes produce a great many, +and as the daughter buds do not always separate from the parent until +they have themselves produced buds, temporary colonies of some +complexity arise; Chun figures a specimen with nineteen daughter and +granddaughter buds[AV]. + + [Footnote AV: Pallas writes as regards this "pulcherrime + vegetantem varietatem" with his usual critical insight, "Vix + tamen peculiaris speciei nomine salutanda videtur." It is + probably the _Hydra socialis_ of Linne.] + +In Europe and N. America there appear to be two races or phases of the +species. To avoid ambiguity they may be called form A and form B and +described as follows:-- + + Form A is of vigorous growth. It is as a rule dioecious, and + its reproductive organs may be borne practically at any + level on the surface of the column. Its eggs are spherical + and as a rule covered almost uniformly with spines. + + Form B is smaller and has smaller and more variable + nettle-cells. Its reproductive organs are borne only on the + distal third or at the base of its column and it is often + monoecious. The lower surface of its egg is flattened, + adherent, and devoid of spines. + +The larger form (A) was originally named _Hydra monoecia_ by Downing, +who in 1904 expressed a wish to substitute for the specific name, which +had been given through inadvertence, the more appropriate one _dioecia_. +As, however, it appears to be the commoner of the two in northern +Europe, we may regard it as probably being the one named _Hydra +oligactis_ by Pallas and therefore may accept it as the _forma typica_ +of that species. According to Brauer (1908) the smaller form is Linne's +_Hydra polypus_; but the original description of the "species" hardly +bears out this view. As reproductive organs have not yet been found in +Indian specimens, it is impossible to say to which of the two forms they +belong. + +A red form of _H. oligactis_ occurs in Tibet in the lake Rham-tso, at an +altitude of about 15,000 feet and has been reported from various small +lakes in mountainous parts of Europe. It is probably the form called +_Hydra rhaetica_ by Asper, but his figures are lacking in detail and +appear to have been drawn from specimens in a state of partial +contraction. _H. rubra_, Lewes (Ann. Mag. Nat. Hist. (3) v, p. 71, +1860), may also be identical with this form. Roux, indeed, states that +_H. rubra_ is only found living unattached at considerable depths (Ann. +Biol. lacustre ii, p. 266, 1907); but this statement does not accord +with the fact that Lewes's specimens were found in ponds on Wimbledon +Common. + +TYPE not in existence. + +GEOGRAPHICAL DISTRIBUTION.--_H. oligactis_ is widely distributed in +Europe and N. America, but in India has only been found in and near the +city of Lahore in the Punjab. + +BIOLOGY.--This species was found by Major J. Stephenson, I.M.S., in the +basin of a fountain at Lahore and in an ornamental canal in the Shalimar +Gardens on the outskirts of the same city. Nothing is known as regards +its habits in this country. In N. America, according to Downing, form B +breeds in September and October and form A from October to December. The +eggs of form B remain attached to the parent until the two cellular +layers are formed and then drop off, whereas those of form A are fixed +by the parent to some extraneous object, its column contracting until +they are in a favourable position for attachment. + +The colour of Indian examples of _H. oligactis_ apparently resembles +that of the Calcutta winter brood of _H. vulgaris_ so far as visual +effect is concerned, but I have noticed in specimens from Lahore and the +neighbourhood that very minute spherical bodies of a dark green colour +are present in the endoderm cells. + + + + + PART III. + + FRESHWATER POLYZOA + + (CTENOSTOMATA & PHYLACTOLAEMATA). + + + + +INTRODUCTION TO PART III. + + +I. + +STATUS AND STRUCTURE OF THE POLYZOA. + +The Polyzoa constitute a class in the third great division of the animal +kingdom, the so-called Triploblastea. In this division are included also +the worms, molluscs, insects, crustacea, spiders, vertebrates, etc.; for +heterogeneous as its elements appear, all these animals may be +considered to have essential features in common, in particular a body +consisting primarily of three cellular layers. Most of them also possess +a body cavity distinct from the alimentary canal. Some authors regard +the position of the polyzoa as near that of the higher worms, but the +group is an isolated one. + +In considering the anatomy of simple forms of animal life such as the +sponges it is necessary to pay attention mainly to individual cells, but +in discussing more complicated forms our notice is first attracted to +tissues and organs, for the cells of which these tissues and organs are +composed have each a definite position, a definite structure, and a +definite function. The most characteristic feature of the polyzoa, +considered from this point of view, is the fact that most of their +organs fall into one of two categories and are connected either with +what is called the "zooecium" or with what is known as the "polypide." +The zooecium is a cage in which the polypide is enclosed, but it is a +living cage, differing from the shell of a snail or the tubes in which +many worms encase themselves in being part of the animal itself. The +polypide consists mainly of the organs connected directly and indirectly +with nutrition and of part of the muscular system; its name is derived +from the fact that it bears a superficial resemblance to a polyp such as +_Hydra_. + +The shape and structure of the zooecium differs greatly in different +groups of polyzoa. In its simplest form it is merely a cylindrical tube +of living matter which secretes an outer horny or gelatinous covering. +It is open at the end furthest from its base, at which it is attached +either to another zooecium or to some kind of supporting structure. +Certain parts of the polypide can always be extruded from the aperture, +which is known technically as the "orifice," or withdrawn through it +into the zooecium. When the polypide is retracted it draws in with it a +portion of the zooecium. The dead outer layer or ectocyst lines part of +the portion thus invaginated and forms the walls of a cavity within the +orifice. The base of this cavity consists in many forms of a transverse +partition pierced in the middle by a circular hole and known as the +"diaphragm." The diaphragm, however, does not constitute the limit of +the invaginated portion of the zooecium, for the living inner wall or +endocyst is dragged in still further and forms a sheath round the +retracted tentacles. When the tentacles are protruded they emerge +through the hole in the diaphragm, carrying with them their sheath of +endocyst. The invagination above the diaphragm, consisting of both +endocyst and ectocyst, is then everted. + +The tentacles are a characteristic feature of the polypide. Together +with the base to which they are attached they are known as the +"lophophore"; they surround the mouth, usually in a circle. They differ +widely from the tentacles of _Hydra_ in both structure and function, +although they too serve as organs for the capture of prey; they are not +highly contractile and are not provided with nettle-cells but are +covered with cilia, which are in constant motion. When extruded they +form a conspicuous calix-like crown to the zooecium, but in the +retracted condition they are closely pressed together and lie parallel +to one another. They are capable individually of motion in all +directions but, although they usually move in concert, they cannot as a +rule seize objects between them. + +The mouth is a hole situated in the midst of the tentacles. It leads +directly into a funnel-shaped oesophagus, the upper part of which is +lined with cilia and is sometimes distinguished as the "pharynx," while +the lower part, the oesophagus proper, is a thin-walled tube that +connects the pharynx with the stomach, which it enters on the dorsal +side. The stomach is a bulky organ that differs markedly in form and +structure in different groups of polyzoa. It is lined internally with +glandular cells and the inner wall is sometimes thrown into folds or +"rugae." The part with which the oesophagus communicates is known as the +"cardiac" portion, while the part whence the intestine originates is +called the "pylorus" or "pyloric" portion. The intestine commences on +the ventral side opposite the entrance of the oesophagus and nearly on a +level with it, the bulk of the stomach depending between the two tubes. +This part of the stomach is often produced into a blind tube, the fundus +or caecum. The alimentary canal may therefore be described as distinctly +Y-shaped. The proximal part of the intestine is in some forms lined with +cilia, and the tube as a whole is usually divided into two parts--the +intestine proper, which is nearest the stomach, and the rectum, which +opens by the anus not far from the mouth. + +The nervous system consists of a central ganglion or brain, which is +situated at the base of the tentacles on the side nearest the anus and +gives out radiating nerves in all directions. Close to the brain and +providing a communication between the cavity of the zooecium and the +cavity in which the tentacles are contained (or, in the case of an +expanded polyp, the external world) is a ciliated tube known as the +"intertentacular organ." Apparently it acts as a passage through which +the genital products are expelled; but contradictory statements have +been made regarding it, and perhaps it is present only at certain +seasons or in certain conditions of the polypide. + +[Illustration: Fig. 30.--Vertical section through a polypide of +_Alcyonidium_ with the polypide retracted (after Prouho). + +A=orifice; B=contracted collar; C=diaphragm; D=parieto-vaginal muscles; +E=tentacles; F=pharynx; G=oesophagus; H=stomach; J=intestine; K=rectum; +L=intertentacular organ; M=retractor muscle; N=testes; O=ovary; +P=funiculus; Q=parietal muscles; R=ectocyst; S=endocyst.] + +The muscular system is often of a complicated nature, but three sets of +muscles may be distinguished as being of peculiar importance, viz., (i) +the retractor muscles, which are fixed to the base of the lophophore at +one end and to the base of the zooecium at the other, and by contracting +pull the former back into the zooecium; (ii) the parieto-vaginal +muscles, which connect the upper part of the invaginated portion of the +zooecium with the main wall thereof; and (iii) the parietal muscles, +which run round the inner wall of the zooecium and compress the zooecium +as a whole. The parietal muscles are not developed in the +Phylactolaemata, the most highly specialized group of freshwater polyzoa. + +The cavity between the polypide and the zooecium contains a reticulate +tissue of cells known as the "funicular" tissue, and this tissue is +usually concentrated to form a hollow strand or strands ("funiculi") +that connect the outer wall of the alimentary canal with the endocyst. + +This rapid sketch of the general anatomy of a simple polyzoon will be +the best understood by comparing it with fig. 30, which represents, in a +somewhat diagrammatic fashion, a vertical section through a single +zooecium and polypide of the order Ctenostomata, to which some of the +freshwater species belong. The polypide is represented in a retracted +condition in which the Y-shaped disposition of the alimentary canal is +somewhat obscured. + +In the great majority of cases the polyzoa form permanent colonies or +polyparia, each of which consists of a number of individual zooecia and +polypides connected together by threads of living tissue. These colonies +are formed by budding, not by independent individuals becoming +associated together. In a few cases compound colonies are formed owing +to the fact that separate simple colonies congregate and secrete a +common investment; but in these cases there is no organic connection +between the constituent colonies. It is only in the small subclass +Entoprocta, the polypides and zooecia of which are not nearly so +distinct from one another as they are in other polyzoa (the Ectoprocta), +that mature solitary individuals occur. + +As representatives of both subclasses of polyzoa and of more than one +order of Ectoprocta occur in fresh water, I have prefaced my description +of the Indian species with a synopsis of the more conspicuous characters +of the different groups (pp. 183-186). + + +CAPTURE AND DIGESTION OF FOOD: ELIMINATION OF WASTE PRODUCTS. + +The food of all polyzoa consists of minute living organisms, but its +exact nature has been little studied as regards individual species and +genera. In _Victorella bengalensis_ it consists largely of diatoms, +while the species of _Hislopia_ and _Arachnoidea_ possess an alimentary +canal modified for the purpose of retaining flagellate organisms until +they become encysted. Similar organisms form a large part of the food of +the phylactolaemata. + +Although the tentacles may be correctly described as organs used in +capturing prey, they do not themselves seize it but waft it by means of +the currents set up by their cilia to the mouth, into which it is swept +by the currents produced by the cilia lining the pharynx. The tentacles +are also able in some species to interlace themselves in order to +prevent the escape of prey. Apparently they have the power of rejecting +unsuitable food, for they may often be observed to bend backwards and +forwards and thrust particles that have approached them away, and if the +water contains anything of a noxious nature in solution the lophophore +is immediately retracted, unless it has been completely paralysed. In +the phylactolaemata the peculiar organ known as the epistome is capable +of closing the mouth completely, and probably acts as an additional +safeguard in preventing the ingestion of anything of an injurious +nature. + +In many genera and larger groups the food commonly passes down the +pharynx into the stomach without interruption, although it is probable +that in all species the oesophagus can be closed off from the stomach by +a valve at its base. In some forms, however, a "gizzard" is interposed +between the oesophagus and the stomach. This gizzard has not the same +function in all cases, for whereas in some forms (_e. g._, in +_Bowerbankia_) it is lined with horny projections and is a powerful +crushing organ, in others (_e. g._, in _Hislopia_ or _Victorella_) it +acts as an antechamber in which food can be preserved without being +crushed until it is required for digestion, or rough indigestible +particles can be retained which would injure the delicate walls of the +stomach. + +Digestion takes place mainly in the stomach, the walls of which are of a +glandular nature. The excreta are formed into oval masses in the rectum +and are extruded from the anus in this condition. + +Although the gross non-nutritious parts of the food are passed _per +anum_, the waste products of the vital processes are not eliminated so +easily, and a remarkable process known as the formation of brown bodies +frequently takes place. This process cannot be described more clearly +and succinctly than by quoting Dr. Harmer's description of it from pp. +471 and 472 of vol. ii. of the Cambridge Natural History, a volume to +which I have been much indebted in the preparation of this introduction. +The description is based very largely on Dr. Harmer's own +observations[AW]. + + [Footnote AW: Q. J. Micr. Sci. xxxiii, p. 123 (1892).] + +"The tentacles, alimentary canal, and nervous system break down, and the +tentacles cease to be capable of being protruded. The degenerating +organs become compacted into a rounded mass, known from its colour as +the 'brown body.' This structure may readily be seen in a large +proportion of the zooecia of transparent species. In active parts of the +colony of the body-wall next develops an internal bud-like structure, +which rapidly acquires the form of a new polypide. This takes the place +originally occupied by the old polypide, while the latter may either +remain in the zooecium in the permanent form of a 'brown body,' or pass +to the exterior. In _Flustra_ the young polypide-bud becomes connected +with the 'brown body' by a funiculus. The apex of the blind pouch or +'caecum' of the young stomach is guided by this strand to the 'brown +body,' which it partially surrounds. The 'brown body' then breaks up, +and its fragments pass into the cavity of the stomach, from which they +reach the exterior by means of the anus." + +Brown bodies are rarely if ever found in the phylactolaemata, in which +the life of the colony is always short; but they are not uncommon in +_Hislopia_ and _Victorella_, although in the case of the former they may +easily escape notice on account of the fact that they are much paler in +colour than is usually the case. When they are found in a ctenostome the +collar-like membrane characteristic of the suborder is extruded from the +orifice (which then disappears) and remains as a conspicuous external +addition to the zooecium, the ectocyst of which, at any rate in +_Bowerbankia_ and _Victorella_, sometimes becomes thickened and dark in +colour. + +It is noteworthy that the colouring matter of the brown bodies is +practically the only colouring matter found in the polypides of most +polyzoa. Young polypides are practically colourless in almost all cases. + + +REPRODUCTION: BUDDING. + +Polyzoa reproduce their species in three ways--(i) by means of eggs, +(ii) by budding, and (iii) by means of bodies developed asexually and +capable of lying dormant in unfavourable conditions without losing their +vitality. + +Most, if not all species are hermaphrodite, eggs and spermatozoa being +produced either simultaneously or in succession by each individual, or +by certain individuals in each zoarium. The reproductive organs are +borne on the inner surface of the endocyst, as a rule in a definite +position, and often in connection with the funiculus or funiculi. It is +doubtful to what extent eggs are habitually fertilized by spermatozoa of +the individual that has borne them, but in some cases this is +practically impossible and spermatozoa from other individuals must be +introduced into the zooecium. + +Budding as a rule does not result in the formation of independent +organisms, but is rather comparable to the proliferation that has become +the normal method of growth in sponges, except of course that +individuality is much more marked in the component parts of a polyzoon +colony than it is in a sponge. In the genera described in this volume +budding takes place by the outgrowth of a part of the body-wall and the +formation therein of a new polypide, but the order in which the buds +appear and their arrangement in reference to the parent zooecium is +different in the different groups. In the freshwater ctenostomes three +buds are typically produced from each zooecium, one at the anterior end +and one at either side, the two latter being exactly opposite one +another. The parent zooecium in this formation arises from another +zooecium situated immediately behind it, so that each zooecium, except +at the extremities of the zoarium, is connected with four other zooecia, +the five together forming a cross. The two lateral buds are, however, +frequently suppressed, or only one of them is developed, and a linear +series of zooecia with occasional lateral branches is formed instead of +a series of crosses. In the phylactolaemata, on the other hand, the +linear method of budding is the typical one, but granddaughter-buds are +produced long before the daughter-buds are mature, so that the zooecia +are frequently pressed together, and lateral buds are produced +irregularly. In _Victorella_ additional adventitious buds are produced +freely near the tip of the zooecium. + +Reproduction by spontaneous fission sometimes occurs, especially in the +Lophopinae, but the process differs from that which takes place when a +_Hydra_ divides into two, for there is no division of individual zooecia +or polypides but merely one of the whole zoarium. + +The production of reproductive bodies analogous to the gemmules of +sponges appears to be confined in the polyzoa to the species that +inhabit fresh or brackish water, nor does it occur in all of these. + +All the phylactolaemata produce, within their zooecia, the bodies known +as statoblasts. These bodies consist essentially of masses of cells +containing abundant food-material and enclosed in a capsule with thick +horny walls. In many cases the capsule is surrounded by a "swim-ring" +composed of a mass of horny-walled chambers filled with air, which +renders the statoblast extremely light and enables it to float on the +surface of the water; while in some genera the margin of the swim-ring +bears peculiar hooked processes, the function of which is obscure. The +whole structure first becomes visible as a mass of cells (the origin of +all of which is not the same) formed in connection with the funiculus, +and the statoblast may be regarded as an internal bud. Its origin and +development in different genera has been studied by several authors, +notably by Oka[AX] in _Pectinatella_, and by Braem[AY] in _Cristatella_. + + [Footnote AX: Journ. Coll. Sci. Tokyo, iv, p. 124 (1891).] + + [Footnote AY: Bibliotheca Zoologica, ii, pt. 6, p. 17 + (1890).] + +The external form of the statoblasts is very important in the +classification of the phylactolaemata, to which these structures are +confined. In all the genera that occur in India they are flattened and +have an oval, circular, or approximately oval outline. + +In temperate climates statoblasts are produced in great profusion at the +approach of winter, but in India they occur, in most species, in +greatest numbers at the approach of the hot weather. + +[Illustration: Fig. 31.--Part of the zoarium of _Victorella bengalensis_ +entirely transformed into resting buds, x 25. (From an aquarium in +Calcutta.)] + +In the family Paludicellidae (ctenostomata) external buds which resemble +the statoblasts in many respects are produced at the approach of +unfavourable climatic conditions, but no such buds are known in the +family Hislopiidae, the zoaria of which appear to be practically +perennial. The buds consist of masses of cells formed at the points at +which ordinary buds would naturally be produced, but packed with +food-material and protected like statoblasts by a thick horny coat. It +seems also that old zooecia and polypides are sometimes transformed into +buds of the kind (fig. 31), and it is possible that there is some +connection between the formation of brown bodies and their production. +Like the statoblasts of the phylactolaemata the resting buds of the +Paludicellidae are produced in Europe at the approach of winter, and in +India at that of the hot weather. + + +DEVELOPMENT. + +(a) _From the Egg._ + +Some polyzoa are oviparous, while in others a larva is formed within the +zooecium and does not escape until it has attained some complexity of +structure. Both the ctenostomatous genera that are found in fresh water +in India are oviparous, but whereas in _Victorella_ the egg is small and +appears to be extruded soon after its fertilization, in _Hislopia_ it +remains in the zooecium for a considerable time, increases to a +relatively large size, and in some unknown manner accumulates a +considerable amount of food-material before escaping. Unfortunately the +development is unknown in both genera. + +In the phylactolaemata the life-history is much better known, having been +studied by several authors, notably by Allman, by Kraepelin, and by +Braem (1908). The egg is contained in a thin membrane, and while still +enclosed in the zooecium, forms by regular division a hollow sphere +composed of similar cells. This sphere then assumes an ovoid form, +becomes covered with cilia externally, and breaks its way through the +egg-membrane into the cavity of the zooecium. Inside the embryo, by a +process analogous to budding, a polypide or a pair of polypides is +formed. Meanwhile the embryo has become distinctly pear-shaped, the +polypide or polypides being situated at its narrow end, in which a pore +makes its appearance. The walls are hollow in the region occupied by the +polypide, the cavity contained in them being bridged by slender threads +of tissue. The larva thus composed makes its way out of the zooecium, +according to Kraepelin through the orifice of a degenerate bud formed +for its reception, and swims about for a short time by means of the +cilia with which it is covered. Its broad end then affixes itself to +some solid object, the polypide is everted through the pore at the +narrow end and the whole of that part of the larva which formerly +enclosed it is turned completely inside out. A zoarium with its included +polypides is finally produced from the young polypide by the rapid +development of buds. + +(b) _From the Statoblast and Resting Buds._ + +There is little information available as regards the development of the +young polyzoon in the resting buds of the freshwater ctenostomes. In +_Paludicella_ and _Pottsiella_ the capsule of the bud splits +longitudinally into two valves and the polypide emerges between them; +but in _Victorella bengalensis_ one of the projections on the margin of +the bud appears to be transformed directly into the tip of a new +zooecium and the capsule is gradually absorbed. + +Contradictory statements have been made as regards several important +points in the development of the statoblast and it is probable that +considerable differences exist in different species. The following facts +appear to be of general application. The cellular contents of the +capsule consist mainly of a mass of cells packed with food-material in a +granular form, the whole enclosed in a delicate membrane formed of flat +cells. When conditions become favourable for development a cavity +appears near one end of the mass and the cells that form its walls +assume a columnar form in vertical section. The cavity increases rapidly +in size, and, as it does so, a young polypide is budded off from its +walls. Another bud may then appear in a similar fashion, and the +zooecium of the first bud assumes its characteristic features. The +capsule then splits longitudinally into two disk-like valves and the +young polypide, in some cases already possessing a daughter bud, emerges +in its zooecium, adheres by its base to some external object and +produces a new polyparium by budding. The two valves of the statoblast +often remain attached to the zoarium that has emerged from between them +until it attains considerable dimensions (see Plate IV, fig. 3 _a_). + +What conditions favour development is a question that cannot yet be +answered in a satisfactory manner. Statoblasts can lie dormant for +months and even for years without losing their power of germinating, and +it is known that in Europe they germinate more readily after being +subjected to a low temperature. In tropical India this is, of course, an +impossible condition, but perhaps an abnormally high temperature has the +same effect. At any rate it is an established fact that whereas the +gemmules of most species germinate in Europe in spring, in Bengal they +germinate either at the beginning of the "rains" or at that of our mild +Indian winter. + + +MOVEMENTS. + +[Illustration: Fig. 32.--Zoarium of _Lophopodella carteri_ moving along +the stem of a water plant, x 4. (From Igatpuri Lake.)] + +In the vast majority of the polyzoa, marine as well as freshwater, +movement is practically confined to the polypide, the external walls of +the zooecium being rigid, the zooecia being closely linked together and +the whole zoarium permanently fixed to some extraneous object. In a few +freshwater species belonging to the genera _Cristatella_, _Lophopus_, +_Lophopodella_ and _Pectinatella_, the whole zoarium has the power of +progression. This power is best developed in _Cristatella_, which glides +along with considerable rapidity on a highly specialized "sole" provided +with abundant mucus and representing all that remains of the ectocyst. +It is by no means clear how the zoaria of the other genera move from one +place to another, for the base is not modified, so far as can be seen, +for the purpose, and the motion is extremely slow. It is probable, +however, that progression is effected by alternate expansions and +contractions of the base, and in _Lophopodella_ (fig. 32), which moves +rather less slowly than its allies, the anterior part of the base is +raised at times from the surface along which it is moving. The whole +zoarium can be released in this way and occasionally drops through the +water, and is perhaps carried by currents from one place to another in +so doing. + +So far as the polypides are concerned, the most important movements are +those which enable the lophophore and the adjacent parts to be extruded +from and withdrawn into the zooecium. The latter movement is executed by +means of the retractor muscles, which by contracting drag the extruded +parts back towards the posterior end of the endocyst, but it is not by +any means certain how the extrusion of the lophophore is brought about. +In most ctenostomes the action of the parietal muscles doubtless assists +in squeezing it out when the retractor and parieto-vaginal muscles +relax, but Oka states that protrusion can be effected in the +phylactolaemata even after the zooecium has been cut open. Possibly some +hydrostatic action takes place, however, and allowance must always be +made for the natural resilience of the inverted portion of the ectocyst. + +Even when the polypide is retracted, muscular action does not cease, for +frequent movements, in some cases apparently rhythmical, of the +alimentary canal may be observed, and in _Hislopia_ contraction of the +gizzard takes place at irregular intervals. + +When the lophophore is expanded, the tentacles in favourable +circumstances remain almost still, except for the movements of their +cilia; but if a particle of matter too large for the mouth to swallow or +otherwise unsuitable is brought by the currents of the cilia towards it, +individual tentacles can be bent down to wave it away and similar +movements are often observed without apparent cause. + +In the cheilostomes certain individuals of each zoarium are often +profoundly modified in shape and function and exhibit almost constant +rhythmical or convulsive movements, some ("avicularia") being shaped +like a bird's beak and snapping together, others ("vibracula") being +more or less thread-like and having a waving motion. + + +DISTRIBUTION OF THE FRESHWATER POLYZOA. + +Fifteen genera of freshwater Polyzoa are now recognized, one +entoproctous and fourteen ectoproctous; five of the latter are +ctenostomatous and nine phylactolaematous. Of the fourteen ectoproctous +genera seven are known to occur in India, viz., _Victorella_, +_Hislopia_, _Fredericella_, _Plumatella_, _Stolella_, _Lophopodella_, +and _Pectinatella_. Except _Stolella_, which is only known from northern +India, these genera have an extremely wide geographical range; +_Victorella_ occurs in Europe, India, Africa, and Australia; _Hislopia_ +in India, Indo-China, China, and Siberia; _Fredericella_ in Europe, N. +America, Africa, India, and Australia; _Plumatella_ in all geographical +regions; _Lophopodella_ in E. and S. Africa, India, and Japan; +_Pectinatella_ in Europe, N. America, Japan, and India. + +Two genera, _Paludicella_ and _Lophopus_, have been stated on +insufficient grounds to occur in India. The former is known from Europe +and N. America, and is said to have been found in Australia, while the +latter is common in Europe and N. America and also occurs in Brazil. + +Of the genera that have not been found in this country the most +remarkable are _Urnatella_ and _Cristatella_. The former is the only +representative in fresh water of the Entoprocta and has only been found +in N. America. Each individual is borne upon a segmented stalk the +segments of which are enclosed in strong horny coverings and are +believed to act as resting buds. _Cristatella_, which is common in +Europe and N. America, is a phylactolaematous genus of highly specialized +structure. It possesses a creeping "sole" or organ of progression at the +base of the zoarium. + +The other phylactolaematous genera that do not occur in India appear to +be of limited distribution, for _Australella_ is only known from N. S. +Wales, and _Stephanella_ from Japan. The ctenostomatous _Arachnoidea_ +has only been reported from Lake Tanganyika, and _Pottsiella_ only from +a single locality in N. America. + +As regards the exotic distribution of the Indian species little need be +said. The majority of the _Plumatellae_ are identical with European +species, while the only species of _Fredericella_ that has been +discovered is closely allied to the European one. The Indian species of +_Lophopodella_ occurs also in E. Africa and Japan, while that of +_Pectinatella_ is apparently confined to India, Burma and Ceylon, but is +closely allied to a Japanese form. + + +POLYZOA OF BRACKISH WATER. + +With the exception of _Victorella_, which occurs more commonly in +brackish than in fresh water and has been found in the sea, the genera +that occur in fresh water are confined or practically confined to that +medium; but certain marine ctenostomes and cheilostomes not uncommonly +make their way, both in Europe and in India, into brackish water, and in +the delta of the Ganges an entoproctous genus also does so. The +ctenostomatous genera that are found occasionally in brackish water +belong to two divisions of the suborder, the Vesicularina and the +Alcyonellea. To the former division belongs _Bowerbankia_, a form of +which (_B. caudata_ subsp. _bengalensis_, p. 187) is often found in the +Ganges delta with _Victorella bengalensis_. No species of Alcyonellea +has, however, as yet been found in Indian brackish waters. The two +Indian cheilostomes of brackish water belong to a genus (_Membranipora_) +also found in similar situations in Europe. One of them (_M. +lacroixii_[AZ]) is, indeed, identical with a European form that occurs +in England both in the sea and in ditches of brackish water. I have +found it in the Cochin backwaters, in ponds of brackish water at the +south end of the Chilka Lake (Ganjam, Madras), on the shore at Puri in +Orissa, and in the Mutlah River at Port Canning. The second species (_M. +bengalensis_, Stoliczka) is peculiar to the delta of the Ganges[BA] and +has not as yet been found in the open sea. The two species are easily +recognized from one another, for whereas the lip of _M. bengalensis_ +(fig. 33) bears a pair of long forked spines, there are no such +structures on that of _M. lacroixii_, the dorsal surface of which is +remarkably transparent. _M. lacroixii_ forms a flat zoarium, the only +part visible to the naked eye being often the beaded margin of the +zooecia, which appears as a delicate reticulation on bricks, logs of +wood, the stems of rushes and of hydroids, etc.; but the zoarium of _M. +bengalensis_ is as a rule distinctly foliaceous and has a peculiar +silvery lustre. + + [Footnote AZ: There is some doubt as to the proper name of + this species, which may not be the one originally described + as _Membranipora lacroixii_ by Andouin. I follow Busk and + Hincks in my identification (see Cat. Polyzoa Brit. Mus. ii, + p. 60, and Hist. Brit. Polyzoa, p. 129). Levinsen calls it + _M. hippopus_, sp. nov. (see Morphological and Systematic + Studies on the Cheilostomatous Bryozoa, p. 144; Copenhagen, + 1909).] + + [Footnote BA: Miss Thornely (Rec. Ind. Mus. i, p. 186, 1907) + records it from Mergui, but this is an error due to an + almost illegible label. The specimens she examined were the + types of the species from Port Canning. Since this was + written I have obtained specimens from Bombay--_April_, + 1911.] + +[Illustration: Fig. 33.--Outline of four zooecia of _Membranipora +bengalensis_, Stoliczka (from type specimen, after Thornely). In the +left upper zooecium the lip is shown open.] + +_Loxosomatoides_[BB] (fig. 34), the Indian entoproctous genus found in +brackish water, has not as yet been obtained from the open sea, but has +recently been introduced, apparently from a tidal creek, into isolated +ponds of brackish water at Port Canning. It is easily recognized by the +chitinous shield attached to the ventral (posterior) surface. + + [Footnote BB: Annandale, Rec. Ind. Mus. ii, p. 14 (1908).] + +[Illustration: Fig. 34.--_Loxosomatoides colonialis_, Annandale. + +A and B, a single individual of form A, as seen (A) in lateral, and (B) +in ventral view; C, outline of a similar individual with the tentacles +retracted, as seen from in front (dorsal view); D, ventral view of an +individual and bud of form B. All the figures are from the type +specimens and are multiplied by about 70.] + + +II. + +HISTORY OF THE STUDY OF THE FRESHWATER POLYZOA. + +The naturalists of the eighteenth century were acquainted with more than +one species of freshwater polyzoon, but they did not distinguish these +species from the hydroids. Trembley discovered _Cristatella_, which he +called "Polype a Panache," in 1741, and Linne described a species of +_Plumatella_ under the name _Tubipora repens_ in 1758, while ten years +later Pallas gave a much fuller description (under the name _Tubularia +fungosa_) of the form now known as _Plumatella fungosa_ or _P. repens_ +var. _fungosa_. Although Trembley, Baker, and other early writers on the +fauna of fresh water published valuable biological notes, the first +really important work of a comprehensive nature was that of Dumortier +and van Beneden, published in 1848. All previous memoirs were, however, +superseded by Allman's Monograph of the Fresh-Water Polyzoa, which was +issued in 1857, and this memoir remains in certain respects the most +satisfactory that has yet been produced. In 1885 Jullien published a +revision of the phylactolaemata and freshwater ctenostomes which is +unfortunately vitiated by some curious lapses in observation, but it is +to Jullien that the recognition of the proper position of _Hislopia_ is +due. The next comprehensive monograph was that of Kraepelin, which +appeared in two parts (1887 and 1892) in the Abhandlungen des Naturwiss. +Vereins of Hamburg. In its detailed information and carefully executed +histological plates this work is superior to any that preceded it or has +since appeared, but the system of classification adopted is perhaps less +liable to criticism than that followed by Braem in his "Untersuchungen," +published in the Bibliotheca Zoologica in 1888. + +During the second half of the nineteenth century and the first decade of +the twentieth several authors wrote important works on the embryology +and anatomy of the phylactolaemata, notably Kraepelin, Braem, and Oka; +but as yet the ctenostomes of fresh water have received comparatively +little attention from anything but a systematic point of view. + +From all points of view both the phylactolaemata and the ctenostomes of +Asia have been generally neglected, except in the case of the Japanese +phylactolaemata, which have been studied by Oka. Although Carter made +some important discoveries as regards the Indian forms, he did not +devote to them the same attention as he did to the sponges. In the case +of the only new genus he described he introduced a serious error into +the study of the two groups by placing _Hislopia_ among the +cheilostomes, instead of in its true position as the type genus of a +highly specialized family of ctenostomes. + +For fuller details as to the history of the study of the freshwater +Polyzoa the student may refer to Allman's and to Kraepelin's monographs. +An excellent summary is given by Harmer in his chapter on the freshwater +Polyzoa in vol. ii. of the Cambridge Natural History; and Loppens has +recently (1908) published in the Annales de Biologie lacustre a concise +survey of the systematic work that has recently been undertaken. +Unfortunately he perpetuates Carter's error as regards the position of +_Hislopia_. + + +BIBLIOGRAPHY OF THE FRESHWATER POLYZOA. + +A very full bibliography of the freshwater Polyzoa will be found in pt. +i. of Kraepelin's "Die Deutschen Suesswasserbryozoen" (1887), while +Loppens, in his survey of the known species (Ann. Biol. lacustre, ii, +1908), gives some recent references. The following list contains the +titles of some of the more important works of reference, of memoirs on +special points such as reproduction and of papers that have a special +reference to Asiatic species. Only the last section is in any way +complete. + +(a) _Works of Reference._ + +1847. VAN BENEDEN, "Recherches sur les Bryozoaires fluviatiles de +Belgique," Mem. Ac. Roy. Belgique, xxi. + +1850. DUMORTIER and VAN BENEDEN, "Histoire Naturelle des Polypes +composes d'eau douce," 2^e partie, Mem. Ac. Roy. Bruxelles, xvi +(complement). + +1856. ALLMAN, "A Monograph of the Fresh-Water Polyzoa" (London). + +1866-1868. HYATT, "Observations on Polyzoa, suborder Phylactolaemata," +Comm. Essex Inst. iv, p. 197, v, p. 97. + +1880. HINCKS, "A History of the British Marine Polyzoa." + +1885. JULLIEN, "Monographie des Bryozoaires d'eau douce," Bull. Soc. +zool. France, x, p. 91. + +1887 & 1892. KRAEPELIN, "Die deutschen Suesswasserbryozoen," Abhandl. +Nat. Vereins Hamburg, x & xii. + +1890. BRAEM, "Untersuchungen des Bryozoen des suessen Wassers," Bibl. +Zool. ii, Heft 6 (Cassel). + +1896. HARMER, Cambridge Natural History, ii, Polyzoa, chap. xviii. + +1899. KORSCHELT and HEIDER, "Embryology of Invertebrates," vol. ii, +chap. xvi. (English edition by Bernard and Woodward, 1899.) + +1908. LOPPENS, "Les Bryozoaires d'eau douce," Ann. Biol. lacustre, iii. +p. 141. + +(b) _Special Works on Embryology, etc._ + +1875. NITSCHE, "Beitraege zur Kenntniss der Bryozoen," Zeitschr. f. wiss. +Zool. xxv (supplement), p. 343. + +1880. REINHARD, "Zur Kenntniss der Suesswasser-Bryozoen," Zool. Anz. iii, +p. 208. + +1888. BRAEM, "Untersuchungen ueber die Bryozoen des suessen Wassers," +Zool. Anz. xi, pp. 503, 533. + +1891. OKA, "Observations on Freshwater Polyzoa," J. Coll. Sci. Tokyo, +iv, p. 89. + +1906. WILCOX, "Locomotion in young colonies of _Pectinatella +magnifica_," Biol. Bull. Wood's Hole, ii. + +1908. BRAEM, "Die geschlechtliche Entwickelung von Fredericella sultana +nebst Beobachtungen ueber die weitere Lebensgeschichte der Kolonien," +Bibl. Zool. xx, Heft 52. + +(c) _Papers that refer specifically to Asiatic species._ + +1851. LEIDY described _Plumatella diffusa_ in Proc. Ac. Philad. v, p. +261 (1851). + +1858. CARTER, "Description of a Lacustrine Bryozoon allied to +_Flustra_," Ann. Nat. Hist. (3) i, p. 169. + +1859. CARTER, "On the Identify in Structure and Composition of the +so-called Seed-like Body of _Spongilla_ with the Winter-egg of the +Bryozoa: and the presence of Starch-granules in each," Ann. Nat. Hist. +(3) iii, p. 331. (Statoblast of _Lophopodella_ described and figured.) + +1862. MITCHELL, "Freshwater Polyzoa," Q. J. Micr. Sci. (new series) ii, +p. 61. ("_Lophopus_" recorded from Madras.) + +1866. HYATT, "Observations on Polyzoa, suborder Phylactolaemata," Comm. +Essex Inst. iv, p. 197. ("_Pectinatella carteri_" named.) + +1869. STOLICZKA, "On the Anatomy of _Sagartia schilleriana_ and +_Membranipora bengalensis_, a new coral and a bryozoon living in +brackish water at Port Canning," J. As. Soc. Bengal, xxxviii, ii, p. 28. + +1880. JULLIEN, "Description d'un nouveau genre de Bryozoaire +Cheilostomien des eaux douces de la Chine et du Cambodge et de deux +especes nouvelles," Bull. Soc. zool. France, v, p. 77. ("_Norodonia_" +described.) + +1885. JULLIEN, "Monographie des Bryozoaires d'eau douce," Bull. Soc. +zool. France, x, p. 91. (_Hislopia_ assigned to the ctenostomes.) + +1887. KRAEPELIN, "Die deutschen Suesswasserbryozoen," Abh. Ver. Hamburg, +x. (_Plumatella philippinensis._) + +1891. OKA, "Observations on Freshwater Polyzoa," J. Coll. Sci. Tokyo, +iv, p. 89. + +1898. MEISSNER, "Die Moosthiere Ost-Afrikas," in Mobius's +Deutsch-Ost-Afrika, iv. (_Lophopodella carteri_ recorded from E. +Africa.) + +1901. KOROTNEFF, "Faunistische Studien am Baikalsee," Biol. Centrbl. +xxi, p. 305. ("_Echinella_" described.) + +1904-1906. ROUSSELET, "On a new Freshwater Polyzoon from Rhodesia, +_Lophopodella thomasi_, gen. et sp. nov.", J. Quekett Club (2) ix, p. +45. (Genus _Lophopodella_ described.) + +1906. ANNANDALE, "Notes on the Freshwater Fauna of India. No. II. The +Affinities of _Hislopia_," J. As. Soc. Bengal (new series) ii, p. 59. + +1906. KRAEPELIN, "Eine Suesswasser-bryozoe (_Plumatella_) aus Java," +Mitth. Mus. Hamburg, xxiii, p. 143. + +1907. ANNANDALE, "Notes on the Freshwater Fauna of India. No. XII. The +Polyzoa occurring in Indian Fresh and Brackish Pools," J. As. Soc. Bengal +(new series) iii, p. 83. + +1907. ANNANDALE, "Statoblasts from the surface of a Himalayan Pond," +Rec. Ind. Mus. i, p. 177. + +1907. ANNANDALE, "The Fauna of Brackish Ponds at Port Canning, Lower +Bengal: I.--Introduction and Preliminary Account of the Fauna," Rec. +Ind. Mus. i, p. 35. + +1907. ANNANDALE, "The Fauna of Brackish Ponds at Port Canning, Lower +Bengal: VI.--Observations on the Polyzoa, with further notes on the +Ponds," Rec. Ind. Mus. i, p. 197. + +1907. ANNANDALE, "Further Note on a Polyzoon from the Himalayas," Rec. +Ind. Mus. i, p. 145. + +1907. ROUSSELET, "Zoological Results of the Third Tanganyika Expedition, +conducted by Dr. W. A. Cunnington, 1904-1905.--Report on the Polyzoa," +P. Z. Soc. London, i, p. 250. (_Plumatella tanganyikae._) + +1907. OKA, "Eine dritte Art von _Pectinatella_ (_P. davenporti_, n. +sp.)," Zool. Anz. xxxi, p. 716. + +1907. APSTEIN, "Das Plancton im Colombo-See auf Ceylon," Zool. Jahrb. +(Syst.) xxv, p. 201. (_Plumatella_ recorded.) + +1907. WALTON, "Notes on _Hislopia lacustris_, Carter," Rec. Ind. Mus. i, +p. 177. + +1907-1908. OKA, "Zur Kenntnis der Suesswasser-Bryozoenfauna von Japan," +Annot. Zool. Japon, vi, p. 117. + +1907-1908. OKA, "Ueber eine neue Gattung von Suesserwasserbryozoen," +Annot. Zool. Japon, vi, p. 277. + +1908. ANNANDALE, "The Fauna of Brackish Ponds at Port Canning, Lower +Bengal: VII.--Further Observations on the Polyzoa with the description +of a new genus of Entoprocta," Rec. Ind. Mus. ii, p. 11. + +1908. ANNANDALE, "Corrections as to the Identity of Indian +Phylactolaemata," Rec. Ind. Mus. ii, p. 110. + +1908. ANNANDALE, "Three Indian Phylactolaemata," Rec. Ind. Mus. ii, p. +169. + +1908. KIRKPATRICK, "Description of a new variety of _Spongilla +loricata_, Weltner," Rec. Ind. Mus. ii, p. 97. (_Hislopia_ recorded from +Burma.) + +1909. ANNANDALE, "Preliminary Note on a new genus of Phylactolaematous +Polyzoa," Rec. Ind. Mus. iii, p. 279. + +1909. ANNANDALE, "A new species of _Fredericella_ from Indian Lakes," +Rec. Ind. Mus. iii. p. 373. + +1909. WALTON, "Large Colonies of _Hislopia lacustris_," Rec. Ind. Mus. +iii, p. 295. + +1910. ANNANDALE, "Materials for a Revision of the Phylactolaematous +Polyzoa of India," Rec. Ind. Mus. v, p. 37. + +1911. WEST and ANNANDALE, "Descriptions of Three Species of Algae +associated with Indian Freshwater Polyzoa," J. As. Soc. Bengal +(_ined._). + + + + +GLOSSARY OF TECHNICAL TERMS USED IN PART III. + + + _Brown body_ A body formed in a zooecium by the degeneration + of a polypide as a preparation + for its regeneration. + + _Cardiac portion_ (of That part which communicates with the + the stomach). oesophagus. + + _Collar_ A longitudinally pleated circular membrane + capable of being thrust out of the orifice + in advance of the lophophore and of + closing together inside the zooecium above + the tentacles when they are retracted. + + _Dorsal surface_ (_Of zooecium_ or _polypide_) the surface + nearest the mouth; (_of statoblast_) the + surface furthest from that by which the + statoblast is attached to the funiculus + during development. + + _Ectocyst_ The outer, structureless layer of the zooecium. + + _Emarginate_ Having a thin or defective triangular area + (of a zooecium) in the ectocyst at the tip. + + _Endocyst_ The inner, living (cellular) layer of the + zooecium. + + _Epistome_ A leaf-like ciliated organ that projects + upwards and forwards over the mouth + between it and the anus. + + _Funiculus_ A strand of tissue joining the alimentary + canal to the endocyst. + + _Furrowed_ Having a thin or defective longitudinal + (of a zooecium) linear streak in the ectocyst on the dorsal + surface. + + _Gizzard_ A chamber of the alimentary canal situated + at the cardiac end of the stomach and + provided internally with a structureless + lining. + + _Intertentacular organ_ A ciliated tube running between the cavity + of the zooecium and the external base of + the lophophore. + + _Keeled_ Having a longitudinal ridge on the dorsal + (of a zooecium) surface. + + _Lophophore_ The tentacles with the base to which they + are attached. + + _Marginal processes_ Chitinous hooked processes on the margin + (of statoblast). of the swim-ring (_q. v._). + + _OEsophagus_ That part of the alimentary canal which + joins the mouth to the stomach. + + _Orifice_ The aperture through which the lophophore + can be protruded from or retracted into + the zooecium. + + _Parietal muscles_ Transverse muscles running round the inner + wall of the zooecium. + + _Parieto-vaginal_ Muscles that surround the orifice, running + _muscles_ between the folds of the zooecium in an + oblique direction. + + _Polyparium_ The whole body of zooecia and polypides + which are in organic connection. + + _Polypide_ The tentacular crown, alimentary canal, + and retractor muscles of a polyzoon-individual. + + _Pyloric portion_ That part which communicates with the + (of the stomach). intestine. + + _Resting bud_ An external bud provided with food-material + in its cells, with a horny external + coat and capable of lying dormant in + unfavourable conditions. + + _Retractor muscles_ The muscles by the action of which the + lophophore can be pulled back into the + zooecium. + + _Statoblast_ An internal bud arising from the funiculus, + containing food-material in its cells, + covered with a horny coat and capable + of lying dormant in unfavourable conditions. + + _Swim-ring_ A ring of polygonal air-spaces surrounding + the statoblast. + + _Ventral surface_ (_Of zooecium_ or _polypide_) the surface + nearest the anus; (_of statoblast_) the surface + by which the statoblast is attached + to the funiculus during development. + + _Zoarium_ The whole body of zooecia which are in + organic connection. + + _Zooecium_ Those parts of the polyzoon-individual + which constitute a case or "house" for + the polypide. + + + + +SYNOPSIS OF THE CLASSIFICATION OF THE POLYZOA. + + + + +I. + +SYNOPSIS OF THE SUBCLASSES, ORDERS, AND SUBORDERS. + +Class POLYZOA. + +Small coelomate animals, each individual of which consists of a +polyp-like organism or polypide enclosed in a "house" or zooecium +composed partly of living tissues. The mouth is surrounded by a circle +of ciliated tentacles that can be retracted within the zooecium; the +alimentary canal, which is suspended in the zooecium, is Y-shaped and +consists of three parts, the oesophagus, the stomach, and the intestine. + + +Subclass ENTOPROCTA. + +The anus as well as the mouth is enclosed in the circle of tentacles and +the zooecium is not very distinctly separated from the polypide. Some +forms are solitary or form temporary colonies by budding. + +Most Entoprocta are marine, but a freshwater genus (_Urnatella_) occurs +in N. America, while the Indian genus _Loxosomatoides_ (fig. 34, p. 176) +is only known from brackish water. + + +Subclass ECTOPROCTA. + +The anus is outside the circle of tentacles and the zooecium can always +be distinguished from the polypide. All species form by budding +permanent communities the individuals in which remain connected together +by living tissue. + + +Order I. GYMNOLAEMATA. + +Ectoproctous polyzoa the polypides of which have no epistome; the +zooecia are in nearly all cases distinctly separated from one another by +transverse perforated plates. + +Most of the Gymnolaemata are marine, but species belonging to two of the +three suborders into which they are divided often stray into brackish +water, while a few genera that belong to one of these two suborders are +practically confined to fresh water. The three suborders are +distinguished as follows:-- + + +Suborder A. _CHEILOSTOMATA._ + +The zooecia are provided with a "lip" or lid hinged to the posterior +margin of the orifice (see fig. 33, p. 175). This lid closes +automatically outside the zooecium or in a special chamber on the +external surface (the "peristome") when the polypide retracts and is +pushed open by the tentacles as they expand. The majority of the zooecia +in each zoarium are more or less distinctly flattened, but some of them +are often modified to form "vibracula" and "avicularia." + +The Cheilostomata are essentially a marine group, but some species are +found in estuaries and even in pools and ditches of brackish water (fig. +33). + + +Suborder B. _CTENOSTOMATA._ + +The zooecia are provided with a collar-like membrane which is pleated +vertically and closes together above the polypide inside the zooecium +when the former is retracted; it is thrust out of the zooecium and +expands into a ring-shaped form just before the tentacles are extruded. +The zooecia are usually more or less tubular, but in some genera and +species are flattened. + +The majority of the Ctenostomata are marine, but some genera are found +in estuaries, while those of one section of the suborder live almost +exclusively in fresh water. + + +Suborder C. _CYCLOSTOMATA._ + +The zooecia are provided neither with a lip nor with a collar-like +membrane. They are tubular and usually have circular orifices. + +The Cyclostomata are exclusively marine. + + +Order II. PHYLACTOLAEMATA. + +Ectoproctous polyzoa the polypides of which have a leaf-shaped organ +called an epistome projecting upwards and forwards within the circle of +tentacles and between the mouth and the anus. The zooecia are not +distinct from one another, but in dendritic forms the zoarium is divided +irregularly by chitinous partitions. + +The Phylactolaemata are, without exception, freshwater species. + + + + +II. + +SYNOPSIS OF THE LEADING CHARACTERS OF THE DIVISIONS OF THE SUBORDER +CTENOSTOMATA. + + +Suborder B. _CTENOSTOMATA._ + +The suborder has been subdivided in various ways by different authors. +The system here adopted is essentially the same as that proposed in a +recent paper by Waters (Journ. Linn. Soc. London, Zool. xxi, p. 231, +1910), but I have thought it necessary to add a fourth division to the +three adopted by that author, namely, the Alcyonellea, Stolonifera, and +Vesicularina. This new division includes all the freshwater genera and +may be known as the Paludicellina. In none of these divisions are the +tentacles webbed at the base. + +The four divisions may be recognized from the following synopsis of +their characteristic features:-- + + +Division I. ALCYONELLEA. + +The zooecia arise directly from one another in a fleshy or gelatinous +mass. The polypide has no gizzard. The species are essentially marine, +but a few are found in brackish water in estuaries. + + +Division II. STOLONIFERA. + +The zooecia arise from expansions in a delicate creeping rhizome or +root-like structure, the order in which they are connected together +being more or less irregular. As a rule (perhaps always) there is no +gizzard. The species are marine. + + +Division III. VESICULARINA. + +The zooecia grow directly from a tubular stem which is usually free and +vertical, their arrangement being alternate, spiral or irregular. There +is a stout gizzard which bears internal chitinous projections and is +tightly compressed when the polypide is retracted. The species are +essentially marine, but a few are found in brackish water. + + +Division IV. PALUDICELLINA, nov. + +The zooecia are arranged in a regular cruciform manner and arise either +directly one from another or with the intervention of tubular processes. +If the polypide has a gizzard it does not bear internal chitinous +projections. Most of the species are confined to fresh water, but a few +are found in brackish water or even in the sea. + +Although all true freshwater Ctenostomes belong to the fourth of these +divisions, species of a genus (_Bowerbankia_) included in the third are +so frequently found in brackish water and in association with one +belonging to the fourth, and are so easily confounded with the latter, +that I think it necessary to include a brief description of the said +genus and of the form that represents it in ponds of brackish water in +India. + + + + +SYSTEMATIC LIST OF THE INDIAN FRESHWATER POLYZOA. + +[The types have been examined in the case of all species, etc., whose +names are marked thus, *.] + + + Order I. GYMNOLAEMATA. + + Suborder I. _CTENOSTOMATA._ + + [Division III. Vesicularina.] + + [Genus BOWERBANKIA, Farre (1837).] + + [_B. caudata_ subsp. _bengalensis_*, Annandale (1907). + (Brackish water).] + + + Division IV. Paludicellina, nov. + + Family I. PALUDICELLIDAE. + + Genus 1. PALUDICELLA, Gervais (1836). + + ? _Paludicella_ sp. (_fide_ Carter). + + Genus 2. VICTORELLA, Kent (1870). + + 26._V. bengalensis_*, Annandale (1907). + + + Family II. HISLOPIIDAE. + + Genus HISLOPIA, Carter (1858). + + 27. _H. lacustris_, Carter (1858). + 27 _a._ _H. lacustris_ subsp. _moniliformis_*, nov. + + + Order II. PHYLACTOLAEMATA. + + Division I. Plumatellina. + + Family 1. FREDERICELLIDAE. + + Genus FREDERICELLA, Gervais (1836). + + 28. _F. indica_*, Annandale (1909). + + + Family 2. PLUMATELLIDAE. + + Subfamily A. PLUMATELLINAE. + + Genus 1. PLUMATELLA, Lamarck (1816). + + 29. _P. fruticosa_, Allman (1844). + 30. _P. emarginata_, Allman (1844). + 31. _P. javanica_*, Kraepelin (1905). + 32. _P. diffusa_, Leidy (1851). + 33. _P. allmani_, Hancock (1850). + 34. _P. tanganyikae_*, Rousselet (1907). + 35. _P. punctata_, Hancock (1850). + + Genus 2. STOLELLA, Annandale (1909). + + 36. _S. indica_*, Annandale (1909). + + + Subfamily B. LOPHOPINAE. + + Genus 1. LOPHOPODELLA, Rousselet (1904). + + 37. _L. carteri_* (Hyatt) (1865). + 37 _a._ _L. carteri_ var. _himalayana_* (Annandale) (1907). + + Genus 2. PECTINATELLA, Leidy (1851). + + 38. _P. burmanica_*, Annandale (1908). + + + Order CTENOSTOMATA. + + [Division VESICULARINA. + + Family VESICULARIDAE. + + VESICULARIDAE, Hincks, Brit. Marine Polyzoa, p. 512 (1880). + +Zooecia constricted at the base, deciduous, attached to a stem that is +either recumbent or vertical. + + +Genus BOWERBANKIA, _Farre_. + + _Bowerbankia_, Farre, Phil. Trans. Roy. Soc. cxxvii, p. 391 (1837). + + _Bowerbankia_, Hincks, _op. cit._ p. 518. + +_Zoarium_ vertical or recumbent. _Zooecia_ ovate or almost cylindrical, +arranged on the stem singly, in clusters or in a subspiral line. +_Polypide_ with 8 or 10 tentacles. + + +Bowerbankia caudata, _Hincks_. + + _Bowerbankia caudata_, Hincks, _op. cit._ p. 521, pl. lxxv, + figs. 7, 8. + +This species is easily distinguished from all others by the fact that +mature zooecia have always the appearance of being fixed to the sides of +a creeping, adherent stem and are produced, below the point at which +they are thus fixed, into a pointed "tail." + + +Subsp. bengalensis, _Annandale_. + + _Bowerbankia caudata_, Thornely, Rec. Ind. Mus. i, p. 196 + (1907). + + _Bowerbankia caudata_, Annandale, _ibid._ p. 203. + + _Bowerbankia caudata_ race _bengalensis_, _id._, _ibid._ + ii. p. 13 (1908). + +The Indian race is only distinguished from the typical form by its +greater luxuriance of growth and by the fact that the "tail" of the +zooecia is often of relatively great length, sometimes equaling or +exceeding the rest of the zooecium. The stem, which is divided at +irregular intervals by partitions, often crosses and recrosses its own +course and even anastomoses, and a fur-like structure is formed in which +the zooecia representing the hairs become much elongated; but upright +branches are never formed. The zoarium has a greenish or greyish tinge. + +TYPE in the Indian Museum. + +GEOGRAPHICAL DISTRIBUTION.--_B. caudata_ subsp. _bengalensis_ is common +in brackish water in the Ganges delta, where it often occurs in close +association with _Victorella bengalensis_, and also at the south end of +the Chilka Lake in the north-east of the Madras Presidency. Although it +has not yet been found elsewhere, it probably occurs all round the +Indian coasts.] + + +Division PALUDICELLINA, nov. + +This division consists of two very distinct families, the species of +which are easily distinguished at a glance by the fact that in one (the +Paludicellidae) the zooecia are tubular, while in the other (the +Hislopiidae) they are broad and flattened. The anatomical and +physiological differences between the two families are important, and +they are associated together mainly on account of the method of budding +by means of which their zoaria are produced. + +[Illustration: Fig. 35.--Single zooecia of _Victorella_ and _Hislopia_ +(magnified). + +A, zooecium of _Victorella pavida_, Kent, with the polypide retracted +(after Kraepelin). + +B, zooecium of _Hislopia lacustris_, Carter (typical form from the +United Provinces), with the collar completely and the tentacles partly +protruded. + +A=collar; B=orifice; C=tentacles; D=pharynx; E=oesophagus proper; +F=gizzard; G=stomach; G'=cardiac portion of stomach; H=intestine; +J=rectum; K=anus; L=young egg; M=green cysts in gizzard; N=testes; +O=ovary; O'=funiculus. + +The muscles are omitted except in fig. B.] + + +Family PALUDICELLIDAE. + + PALUDICELLIDAE, Allman, Mon. Fresh-Water Polyzoa, p. 113 + (1857). + + HOMODIAETIDAE, Kent, Q. J. Micr. Sci. x, p. 35 (1870). + + VICTORELLIDAE, Hincks, Brit. Marine Polyzoa, p. 558 (1880). + + PALUDICELLIDEES, Jullien, Bull. Soc. zool. France, x, p. 174 + (1885). + + PALUDICELLIDES, Loppens, Ann. Biol. lacustre, iii, p. 170 + (1908). + + VICTORELLIDES, _id._, _ibid._ p. 171. + +_Zoarium._ The zoarium is recumbent or erect, and is formed typically +either of zooecia arising directly in cruciform formation from one +another, or of zooecia joined together in similar formation with the +intervention of tubules arising from their own bases. Complications +often arise, however, either on account of the suppression of the +lateral buds of a zooecium, so that the formation becomes linear instead +of cruciform, or by the production in an irregular manner of additional +tubules and buds from the upper part of the zooecia. A confused and +tangled zoarium may thus be formed, the true nature of which can only be +recognized by the examination of its terminal parts. + +_Zooecia._ The zooecia are tubular and have a terminal or subterminal +orifice, which is angulate or subangulate as seen from above. Owing to +this fact, to the stiff nature of the external ectocyst, to the action +of circular muscles that surround the tentacular sheath, and to the +cylindrical form of the soft inverted part, the orifice, as seen from +above, appears to form four flaps or valves, thus [illustration: sketch, +similar to a cloverleaf inside a square with rounded corners]. + +_Polypide._ The alimentary canal is elongate and slender as a whole, the +oesophagus (including the pharynx) being of considerable length. In +_Paludicella_ and _Pottsiella_ the oesophagus opens directly into the +cardiac limb of the stomach, which is distinctly constricted at its +base; but in _Victorella_ the base of the oesophagus is constricted off +from the remainder to form an elongate oval sac the walls of which are +lined with a delicate structureless membrane. _Victorella_ may therefore +be said to possess a gizzard, but the structure that must be so +designated has not the function (that of crushing food) commonly +associated with the name, acting merely as a chamber for the retention +of solid particles. In this genus the cardiac limb of the stomach is +produced and vertical but not constricted at the base. The tentacles in +most species number 8, but in _Paludicella_ there are 16. + +_Resting buds._ The peculiar structures known in Europe as "hibernacula" +are only found in this family. The name hibernacula, however, is +inappropriate to the only known Indian species as they are formed in +this country at the approach of summer instead of, as in Europe and N. +America, at that of winter. It is best, therefore, to call them "resting +buds." They consist of masses of cells congregated at the base of the +zooecia, gorged with food material and covered with a resistant horny +covering. + +The family Paludicellidae consists of three genera which may be +distinguished as follows:-- + + I. Orifice terminal; main axis of the zooecium + vertical; zooecia separated from one another + by tubules. + [A. Base of the zooecia not swollen; no + adventitious buds POTTSIELLA.] + B. Base of the zooecium swollen; adventitious + buds produced near the tip VICTORELLA, p. 194. + II. Orifice subterminal, distinctly on the dorsal + surface; main axis of the zooecium horizontal + (the zoarium being viewed from the dorsal + surface); buds not produced at the tip of the + zooecia PALUDICELLA, p. 192. + +Of these three genera, _Pottsiella_ has not yet been found in India and +is only known to occur in N. America. It consists of one species, _P. +erecta_ (Potts) from the neighbourhood of Philadelphia in the United +States. + +_Victorella_ includes four species, _V. pavida_ known from England and +Germany and said to occur in Australia, _V. muelleri_ from Germany +(distinguished by possessing parietal muscles at the tip of the +zooecia), _V. symbiotica_ from African lakes and _V. bengalensis_ from +India. These species are closely related. + +_Paludicella_ is stated by Carter to have been found in Bombay, but +probably what he really found was the young stage of _V. bengalensis_. A +single species is known in Europe and N. America, namely _P. +ehrenbergi_, van Beneden (=_Alcyonella articulata_, Ehrenberg). + +I have examined specimens of all the species of this family as yet +known. + + +Genus 1. PALUDICELLA, _Gervais_. + + _Paludicella_, Gervais, Compt. Rend. iii, p. 797 (1836). + + _Paludicella_, Allman, Mon. Fresh-Water Polyzoa, p. 113 + (1857). + + ? _Paludicella_, Carter, Ann. Nat. Hist. (3) iii, p. 333 + (1859). + + _Paludicella_, Jullien, Bull. Soc. zool. France, x, p. 174 + (1885). + + _Paludicella_, Kraepelin, Deutsch. Suesswasserbryozoen, i, p. + 96 (1887). + + _Paludicella_, Loppens, Ann. Biol. lacustre, iv, p. 14 + (1910). + +_Zoarium._ The nature of the zoarium in this genus is well expressed by +Ehrenberg's specific name "_articulata_," although the name was given +under a false impression. The zooecia arise directly from one another in +linear series with occasional side-branches. The side-branches are, +however, often suppressed. The zoarium as a whole is either recumbent +and adherent or at least partly vertical. + +_Zooecia._ Although the zooecia are distinctly tubular as a whole, two +longitudinal axes may be distinguished in each, for the tip is bent +upwards in a slanting direction, bearing the orifice at its extremity. +The main axis is, however, at right angles to the dorso-ventral axis, +and the dorsal surface, owing to the position of the aperture, can +always be readily distinguished from the ventral, even when the position +of the zooecium is vertical. Each zooecium tapers towards the posterior +extremity. Parietal muscles are always present. + +[Illustration: Fig. 36.--Structure of _Paludicella ehrenbergi_ (A and B +after Allman). + +A=a single zooecium with the polypide retracted. B=the base of the +lophophore as seen from above with the tentacles removed. C=the orifice +of a polypide with the collar expanded and the tentacles partly +retracted. _a_=tentacles; _c_=collar; _d_=mouth; _e_=oesophagus; +_f_=stomach; _g_=intestine; _k_=parieto-vaginal muscles; _p_=parietal +muscles; _o_=cardiac part of the stomach; _r_=retractor muscle; +_s_=funiculus.] + +_Polypide._ The most striking features of the polypide are the absence +of any trace of a gizzard and the highly specialized form assumed by the +cardiac part of the stomach. There are two funiculi, both connecting the +pyloric part of the stomach with the endocyst. The ovary develops at the +end of the upper, the testis at that of the lower funiculus. + +_Resting buds._ The resting buds are spindle-shaped. + +Kraepelin recognized two species in the genus mainly by their method of +growth and the number of tentacles. In his _P. muelleri_ the zoarium is +always recumbent and the polypide has 8 tentacles, whereas in _P. +articulata_ or _ehrenbergi_ the tentacles number 16 and upright branches +are usually developed. It is probable, however, that the former species +should be assigned to _Victorella_, for it is often difficult to +distinguish _Paludicella_ from young specimens of _Victorella_ unless +the latter bear adventitious terminal buds. The gizzard of _Victorella_ +can be detected in well-preserved material even under a fairly low power +of the microscope, and I have examined specimens of what I believe to be +the adult of _muelleri_ which certainly belong to that genus. + +It is always difficult to see the collar of _Paludicella_, because of +its transparency and because of the fact that its pleats are apparently +not strengthened by chitinous rods as is usually the case. Allman +neither mentions it in his description of the genus nor shows it in his +figures, and Loppens denies its existence, but it is figured by +Kraepelin and can always be detected in well-preserved specimens, if +they are examined carefully. If the collar were actually absent, its +absence would separate _Paludicella_ not only from _Victorella_ and +_Pottsiella_, but also from all other ctenostomes. In any case, +_Victorella_ is distinguished from _Paludicella_ and _Pottsiella_ by +anatomical peculiarities (_e. g._, the possession of a gizzard and the +absence of a second funiculus) that may ultimately be considered +sufficiently great to justify its recognition as the type and only genus +of a separate family or subfamily. + +The description of _Paludicella_ is included here on account of Carter's +identification of the specimens he found at Bombay; but its occurrence +in India is very doubtful. + + +Genus 2. _VICTORELLA_, _Kent_. + + _Victorella_, Kent, Q. J. Micr. Sci. x, p. 34 (1870). + + _Victorella_, Hincks, Brit. Marine Polyzoa, p. 559 (1880). + + _Victorella_, Kraepelin, Deutsch. Suesswasserbryozoen, i, p. + 93 (1887). + +TYPE, _Victorella pavida_, Kent. + +_Zoarium._ The zoarium consists primarily of a number of erect or +semi-erect tubular zooecia joined together at the base in a cruciform +manner by slender tubules, but complications are introduced by the fact +that adventitious buds and tubules are produced, often in large numbers, +round the terminal region of the zooecia, and that these buds are often +separated from their parent zooecium by a tubule of considerable length, +and take root among other zooecia at a distance from their point of +origin. A tangled mass may thus be formed in which it is difficult to +recognize the regular arrangement of the zooecia that can be readily +detached at the growing points of the zoarium. + +_Zooecia._ The zooecia when young closely resemble those of +_Paludicella_, but as they grow the terminal upturned part increases +rapidly, while the horizontal basal part remains almost stationary and +finally appears as a mere swelling at the base of an almost vertical +tube, in which by far the greater part, if not the whole, of the +polypide is contained. Round the terminal part of this tube adventitious +buds and tubules are arranged more or less regularly. There are no +parietal muscles. + +_Polypide._ The polypide has 8 slender tentacles, which are thickly +covered with short hairs. The basal part of the oesophagus forms a +thin-walled sac (the "gizzard") constricted off from the upper portion +and bearing internally a thin structureless membrane. Circular muscles +exist in its wall but are not strongly developed on its upper part. +There is a single funiculus, which connects the posterior end of the +stomach with the base of the zooecium. The ovaries and testes are borne +on the endocyst, not in connection with the funiculus. + +_Resting buds._ The resting buds are flattened or resemble young zooecia +in external form. + +_Victorella_, although found in fresh water, occurs more commonly in +brackish water and is known to exist in the littoral zone of the sea. + + +26. Victorella bengalensis, _Annandale_. + + _Victorella pavida_, Annandale (_nec_ Kent), Rec. Ind. Mus. + i, p. 200, figs. 1-4 (1907). + + _Victorella bengalensis_, _id._, _ibid._ ii, p. 12, fig. 1 + (1908). + +_Zoarium._ _The mature zoarium resembles a thick fur_, the hairs of +which are represented by elongate, erect, slender tubules (the zooecia), +the arrangement of the whole being very complicated and irregular. The +base of the zoarium often consists of an irregular membrane formed of +matted tubules, which are sometimes agglutinated together by a gummy +secretion. The zoarium as a whole has a faint yellowish tinge. + +_Zooecia._ The zooecia when young are practically recumbent, each being +of an ovoid form and having a stout, distinctly quadrate orificial +tubule projecting upwards and slightly forwards near the anterior margin +of the dorsal surface. At this stage a single tubule, often of great +relative length, is often given off near the orifice, bearing a bud at +its free extremity. As the zooecium grows the tubular part becomes much +elongated as compared with the basal part and assumes a vertical +position. Its quadrate form sometimes persists but more often +disappears, so that it becomes almost circular in cross-section +throughout its length. Buds are produced near the tip in considerable +profusion. As a rule, if they appear at this stage, the tubule +connecting them with the parent zooecium is short or obsolete; sometimes +they are produced only on one side of the zooecium, sometimes on two. +The buds themselves produce granddaughter and great-granddaughter buds, +often connected together by short tubules, while still small and +imperfectly developed. The swelling at the base of the zooecium, when +the latter is fully formed, is small. + +_Polypide._ The polypide has the features characteristic of the genus. +The base of the gizzard is surrounded by a strong circular muscle. + +[Illustration: Fig. 37.--_Victorella bengalensis_ (type specimens). + +A=single zooecium without adventitious buds but with a young resting bud +(_b_), x 70 (dorsal view); B=lateral view of a smaller zooecium without +buds, x 70; C=upper part of a zooecium with a single adventitious bud, x +70; D=outline of the upper part of a zooecium with adventitious buds of +several generations, x 35; E=remains of a zooecium with two resting buds +(_b_) attached. All the specimens figured are from Port Canning and, +except D, are represented as they appear when stained with borax carmine +and mounted in canada balsam.] + +_Resting buds._ The resting buds (fig. 31, p. 170) are somewhat variable +in shape but are always flat with irregular cylindrical or +subcylindrical projections round the margin, on which the horny coat is +thinner than it is on the upper surface. This surface is either smooth +or longitudinally ridged. + +TYPE in the Indian Museum. + +This species differs from the European _V. pavida_ in very much the same +way as, but to a greater extent than, the Indian race of _Bowerbankia +caudata_ does from the typical English one (see p. 189). The growth of +the zoarium is much more luxuriant, and the form of the resting buds is +different. + +GEOGRAPHICAL DISTRIBUTION.--_V. bengalensis_ is abundant in pools of +brackish water in the Ganges delta and in the Salt Lakes near Calcutta; +it also occurs in ponds of fresh water near the latter. I have received +specimens from Madras from Dr. J. R. Henderson, and it is probable that +the form from Bombay referred by Carter to _Paludicella_ belonged to +this species. + +BIOLOGY.--In the Ganges delta _V. bengalensis_ is usually found coating +the roots and stems of a species of grass that grows in and near +brackish water, and on sticks that have fallen into the water. It also +spreads over the surface of bricks, and I have found a specimen on a +living shell of the common mollusc _Melania tuberculata_. Dr. Henderson +obtained specimens at Madras from the surface of a freshwater shrimp, +_Palaemon malcolmsonii_. In the ponds at Port Canning the zoaria grow +side by side with, and even entangled with those of _Bowerbankia +caudata_ subsp. _bengalensis_, to the zooecia of which their zooecia +bear a very strong external resemblance so far as their distal extremity +is concerned. This resemblance, however, disappears in the case of +zooecia that bear terminal buds, for no such buds are borne by _B. +caudata_; and the yellowish tint of the zoaria of _V. bengalensis_ is +characteristic. Zoaria of the entoproct _Loxosomatoides colonialis_ and +colonies of the hydroid _Irene ceylonensis_ are also found entangled +with the zoaria of _V. bengalensis_, the zooecia of which are often +covered with various species of Vorticellid protozoa and small rotifers. +The growth of _V. bengalensis_ is more vigorous than that of the other +polyzoa found with it, and patches of _B. caudata_ are frequently +surrounded by large areas of _V. bengalensis_. + +The food of _V. bengalensis_ consists largely of diatoms, the siliceous +shells of which often form the greater part of its excreta. Minute +particles of silt are sometimes retained in the gizzard, being +apparently swallowed by accident. + +There are still many points to be elucidated as regards the production +and development of the resting buds in _V. bengalensis_, but two facts +are now quite clear as regards them: firstly, that these buds are +produced at the approach of the hot weather and germinate in November or +December; and secondly, that the whole zoarium may be transformed at the +former season into a layer of resting buds closely pressed together but +sometimes exhibiting in their arrangement the typical cruciform +formation. Resting buds may often be found in vigorous colonies as late +as the beginning of December; these buds have not been recently formed +but have persisted since the previous spring and have not yet +germinated. Sometimes only one or two buds are formed at the base of an +existing zooecium (fig. 37 _a_), but apparently it is possible not only +for a zooecium to be transformed into a resting bud but for it to +produce four other buds round its base before undergoing the change. +Young polypides are formed inside the buds and a single zooecium sprouts +out of each, as a rule by the growth of one of the basal projections, +when conditions are favourable. + +Polypides of _V. bengalensis_ are often transformed into brown bodies. +When this occurs the orifice closes together, with the collar expanded +outside the zooecium. I have occasionally noticed that the ectocyst of +such zooecia was distinctly thicker and darker in colour than that of +normal zooecia. + +Eggs and spermatozoa are produced in great numbers, as a rule +simultaneously in the same zooecia, but individuals kept in captivity +often produce spermatozoa only. The eggs are small and are set free as +eggs. Nothing is known as regards their development. + +Polypides are as a rule found in an active condition only in the cold +weather, but I have on one occasion seen them in this condition in +August, in a small zoarium attached to a shell of _Melania tuberculata_ +taken in a canal of brackish water near Calcutta. + + +Family HISLOPIIDAE. + + HISLOPIDEES, Jullien, Bull. Soc. zool. France, x, p. 180 + (1885). + + HISLOPIIDAE, Annandale, Rec. Ind. Mus. i, p. 200 (1907). + +_Zoarium_ recumbent, often forming an almost uniform layer on solid +subjects. + +_Zooecia_ flattened, adherent; the orifice dorsal, either surrounded by +a chitinous rim or situated at the tip of an erect chitinous tubule; no +parietal muscles. + +_Polypide_ with an ample gizzard which possesses a uniform chitinous +lining and does not close together when the polypide is retracted. + +_Resting bud_, not produced. + +Only two genera can be recognized in this family, _Arachnoidea_, Moore, +from Central Africa, and _Hislopia_, Carter, which is widely distributed +in Eastern Asia. The former genus possesses an upright orificial tubule +and has zooecia separated by basal tubules. Its anatomy is imperfectly +known, but it certainly possesses a gizzard of similar structure to that +of _Hislopia_, between which and _Victorella_ its zooecium is +intermediate in form. + + +Genus HISLOPIA, _Carter_. + + _Hislopia_, Carter, Ann. Nat. Hist. (3) i, p. 169 (1858). + + _Hislopia_, Stolickza, J. As. Soc. Bengal, xxxviii (2), p. + 61 (1869). + + _Norodonia_, Jullien, Bull. Soc. zool. France, v, p. 77 + (1880). + + _Hislopia_, _id._, _ibid._ x, p. 183 (1885). + + _Norodonia_, _id._, _ibid._ p. 180. + + _Echinella_, Korotneff, Biol. Centrbl. xxi, p. 311 (1901). + + _Hislopia_, Annandale, J. As. Soc. Bengal (new series) ii, + p. 59 (1906). + + _Hislopia_, Loppens, Ann. Biol. lacustre, iii, p. 175 + (1908). + +TYPE, _Hislopia lacustris_, Carter. + +_Zoarium._ The zoarium consists primarily of a main axis running in a +straight line, with lateral branches that point forwards and outwards. +Further proliferation, however, often compacts the structure into an +almost uniform flat area. + +_Zooecia._ The zooecia (fig. 35 B, p. 190) are flat and have the orifice +surrounded by a chitinous rim but not much raised above the dorsal +surface. They arise directly one from another. + +_Polypide._ The polypide possesses from 12 to 20 tentacles. Its +funiculus is rudimentary or absent. Neither the ovaries nor the testes +have any fixed position on the lateral walls of the zooecium to which +they are confined. + +The position of this genus has been misunderstood by several zoologists. +Carter originally described _Hislopia_ as a cheilostome allied to +_Flustra_; in 1880 Jullien perpetuated the error in describing his +_Norodonia_, which was founded on dried specimens of Carter's genus; +while Loppens in 1908 still regarded the two "genera" as distinct and +placed them both among the cheilostomes. In 1885, however, Jullien +retracted his statement that _Norodonia_ was a cheilostome and placed +it, together with _Hislopia_, in a family of which he recognized the +latter as the eponymic genus. Carter's mistake arose from the fact that +he had only examined preserved specimens, in which the thickened rim of +the orifice is strongly reminiscent of the "peristome" of certain +cheilostomes, while the posterior of the four folds into which the +tentacle sheath naturally falls (as in all ctenostomes, _cf._ the +diagram on p. 191) is in certain conditions rather larger than the other +three and suggests the "lip" characteristic of the cheilostomes. If +living specimens are examined, however, it is seen at once that the +posterior fold, like the two lateral folds and the anterior one, changes +its form and size from time to time and has no real resemblance to a +"lip." + +That there is a remarkable, if superficial, resemblance both as regards +the form of the zooecium and as regards the method of growth between +_Hislopia_ and certain cheilostomes cannot be denied, but the structure +of the orifice and indeed of the whole organism is that of a ctenostome +and the resemblance must be regarded as an instance of convergence +rather than of genetic relationship. + +The most striking feature of the polypide of _Hislopia_ is its gizzard +(fig. 38, p. 201) which is perhaps unique (except for that of +_Arachnoidea_) both in structure and function. In structure its +peculiarities reside mainly in three particulars: (i), it is not +constricted off directly from the thin-walled oesophageal tube, but +possesses at its upper extremity a thick-walled tubular portion which +can be entirely closed from the oesophagus at its upper end but always +remains in communication with the spherical part of the gizzard; (ii), +this spherical part of the gizzard is uniformly lined with a thick +chitinous or horny layer which in optical section has the appearance of +a pair of ridges; and (iii), there is a ring of long and very powerful +cilia round the passage from the gizzard to the stomach. The cardiac +limb of the stomach, which is large and heart-shaped, is obsolete. The +wall of the spherical part of the gizzard consists of two layers of +cells, an outer muscular layer consisting of powerful circular muscles +and an inner glandular layer, which secretes the chitinous lining. The +inner walls of the tubular part consist of non-ciliated columnar cells, +and when the polypide is retracted it lies almost at right angles to the +main axis of the zooecium. + +The spherical part of the gizzard invariably contains a number of green +cells, which lie free in the liquid it holds and are kept in motion by +the cilia at its lower aperture. The majority of these cells can be seen +with the aid of a high power of the microscope to consist of a hard +spherical coat or cyst containing green protoplasm in which a spherical +mass of denser substance (the nucleus) and a number of minute +transparent granules can sometimes be detected. The external surface of +many of the cysts is covered with similar granules, but some are quite +clean. + +There can be no doubt that these cysts represent a stage in the +life-history of some minute unicellular plant or animal. Indeed, +although it has not yet been found possible to work out this +life-history in detail, I have been able to obtain much evidence that +they are the resting stage of a flagellate organism allied to _Euglena_ +which is swallowed by the polyzoon and becomes encysted in its gizzard, +extruding in so doing from its external surface a large proportion of +the food-material that it has stored up within itself in the form of +transparent granules. It may also be stated that some of the organisms +die and disintegrate on being received into the gizzard, instead of +encysting themselves. + +So long as the gizzard retains its spherical form the green cells and +its other contents are prevented from entering the stomach by the +movements of the cilia that surround its lower aperture, but every now +and then, at irregular intervals, the muscles that form its outer wall +contract. The chitinous lining although resilient and not inflexible is +too stiff to prevent the lumen of the gizzard being obliterated, but the +action of the muscles changes its contents from a spherical to an ovoid +form and in so doing presses a considerable part of them down into the +stomach, through the ring of the cilia. + +[Illustration: Fig. 38.--Optical section of gizzard of _Hislopia +lacustris_, with contained green cysts, x 240.] + +The contraction of the gizzard is momentary, and on its re-expansion +some of the green cysts that have entered the stomach are often +regurgitated into it. Some, however, remain in the stomach, in which +they are turned round and round by the action of the cilia at both +apertures. They are apparently able to retain their form for some hours +in these circumstances but finally disintegrate and disappear, being +doubtless digested by the juices poured out upon them by the glandular +lining of the stomach. In polypides kept under observation in clean +tap-water all the cysts finally disappear, and the faeces assume a green +colour. In preserved specimens apparently unaltered cysts are sometimes +found in the rectum, but this is exceptional: I have observed nothing of +the kind in living polypides. Cysts often remain for several days +unaltered in the gizzard. + +Imperfect as these observations are, they throw considerable light on +the functions of the gizzard in _Hislopia_. Primarily it appears to act +as a food-reservoir in which the green cysts and other minute organisms +can be kept until they are required for digestion. When in the gizzard +certain organisms surrender a large proportion of the food-material +stored up for their own uses, and this food-material doubtless aids in +nourishing the polyzoon. Although the cysts in the gizzard are +frequently accompanied by diatoms, the latter are not invariably +present. The cysts, moreover, are to be found in the zooecia of +polypides that have formed brown bodies, often being actually enclosed +in the substance of the brown body. The gizzards of the specimens of +_Arachnoidea_ I have examined contain cysts that resemble those found in +the same position in _Hislopia_. + +_Hislopia_ is widely distributed in the southern part of the Oriental +Region, and, if I am right in regarding _Echinella_, Korotneff as a +synonym, extends its range northwards to Lake Baikal. It appears to be a +highly specialized form but is perhaps related, through _Arachnoidea_, +to _Victorella_. + + +27. Hislopia lacustris, _Carter_. + + _Hislopia lacustris_, Carter, Ann. Nat. Hist. (3) i, p. 170, + pl. vii, figs. 1-3 (1858). + + _Norodonia cambodgiensis_, Jullien, Bull. Soc. zool. France, + v, p. 77, figs. 1-3 (1880). + + _Norodonia sinensis_, _id._, _ibid._ p. 78, figs. 1-3. + + _Norodonia cambodgiensis_, _id._, _ibid._ x, p. 181, figs. + 244, 245 (1885). + + _Norodonia sinensis_, _id._, _ibid._ p. 182, figs. 246, 247. + + _Hislopia lacustris_, Annandale, J. As. Soc. Bengal (new + series) iii, p. 85 (1907). + + _Hislopia lacustris_, Walton, Rec. Ind. Mus. i, p. 177 + (1907). + + _Hislopia lacustris_, Kirkpatrick, _ibid._ ii, p. 98 (1908). + + _Hislopia lacustris_, Walton, _ibid._ iii, p. 295 (1909). + +_Zoarium._ The zoarium forms a flat, more or less solid layer and is +closely adherent to foreign objects. As a rule it covers a considerable +area, with radiating branches at the edges; but when growing on slender +twigs or the stems of water-plants it forms narrow, closely compressed +masses. One zooecium, however, never grows over another. + +_Zooecia._ The zooecia are variable in shape. In zoaria which have space +for free expansion they are as a rule irregularly oval, the posterior +extremity being often narrower than the anterior; but small triangular +zooecia and others that are almost square may often be found. When +growing on a support of limited area the zooecia are smaller and as a +rule more elongate. The orifice is situated on a slight eminence nearer +the anterior than the posterior margin of the dorsal surface. It is +surrounded by a strong chitinous rim, which is usually square or +subquadrate but not infrequently circular or subcircular. Sometimes a +prominent spine is borne at each corner of the rim, but these spines are +often vestigial or absent; they are rarely as long as the transverse +diameter of the orifice. The zooecium is usually surrounded by a +chitinous margin, and outside this margin there is often a greater or +less extent of adherent membrane. In some zooecia the margin is obsolete +or obsolescent. The dorsal surface is of a glassy transparency but by no +means soft. + +[Illustration: Fig. 39.--_Hislopia lacustris._ + +A=part of a zoarium of the subspecies _moniliformis_ (type specimen, +from Calcutta), x 15; A=green cysts in gizzard; E=eggs. + +B=outline of part of a zoarium of the typical form of the species from +the United Provinces, showing variation in the form of the zooecia and +of the orifice, x 15.] + +_Polypide._ The polypide has from 12 to 20 tentacles, 16 being a common +number. + +TYPE probably not in existence. It is not in the British Museum and +Prof. Dendy, who has been kind enough to examine the specimens from +Carter's collection now in his possession, tells me that there are none +of _Hislopia_ among them. + + +27 _a._ Subsp. moniliformis, nov. + + _Hislopia lacustris_, Annandale, J. As. Soc. Bengal (new + series) ii, p. 59, fig. 1 (1906). + +In this race, which is common in Calcutta, the zooecia are almost +circular but truncate or concave anteriorly and posteriorly. They form +linear series with few lateral branches. I have found specimens +occasionally on the shell of _Vivipara bengalensis_, but they are much +more common on the leaves of _Vallisneria spiralis_. + +TYPE in the Indian Museum. + +The exact status of the forms described by Jullien as _Norodonia +cambodgiensis_ and _N. sinensis_ is doubtful, but I see no reason to +regard them as specifically distinct from _H. lacustris_, Carter, of +which they may be provisionally regarded as varieties. The variety +_cambodgiensis_ is very like my subspecies _moniliformis_ but has the +zooecia constricted posteriorly, while var. _sinensis_, although the +types were found on _Anodonta_ shells on which there was plenty of room +for growth, resemble the confined phase of _H. lacustris_ so far as the +form of their zooecia and of the orifice is concerned. + +GEOGRAPHICAL DISTRIBUTION.--The typical form is common in northern India +and occurs also in Lower Burma; the subspecies _moniliformis_ appears to +be confined to Lower Bengal, while the varieties _cambodgiensis_ and +_sinensis_ both occur in China, the former having been found also in +Cambodia and Siam. Indian and Burmese localities are:--BENGAL, Calcutta +(subsp. _moniliformis_); Berhampur, Murshidabad district (_J. Robertson +Milne_): CENTRAL PROVINCES, Nagpur (_Carter_): UNITED PROVINCES, +Bulandshahr (_H. J. Walton_): BURMA, Pegu-Sittang Canal (_Kirkpatrick_). + +BIOLOGY.--Regarding the typical form of the species Major Walton writes +(Rec. Ind. Mus. iii, p. 296):--"In volume i (page 177) of the Records of +the Indian Museum, I described the two forms of colonies of _Hislopia_ +that I had found in the United Provinces (Bulandshahr). Of these, one +was a more or less linear arrangement of the zooecia on leaves and +twigs, and the other, and more common, form was an encrusting sheath on +the outer surface of the shells of _Paludina_. During the present +'rains' (July 1908) I have found many examples of what may be considered +a much exaggerated extension of the latter form. These colonies have +been on bricks, tiles, and other submerged objects. The largest colony +that I have seen so far was on a tile; one side of the tile was exposed +above the mud of the bottom of the tank, and its area measured about 120 +square inches; the entire surface was almost completely covered by a +continuous growth of _Hislopia_. Another large colony was on a piece of +bark which measured 7 inches by 3 inches; both sides were practically +everywhere covered by _Hislopia_." + +Major Walton also notes that in the United Provinces the growth of +_Hislopia_ is at its maximum during "rains," and that at that time of +year almost every adult _Paludina_ in a certain tank at Bulandshahr had +its shell covered with the zooecia. The Calcutta race flourishes all the +year round but never forms large or closely compacted zoaria, those on +shells of _Vivipara_ exactly resembling those on leaves of +_Vallisneria_. + +In Calcutta both eggs and spermatozoa are produced at all times of the +year simultaneously in the same zooecia, but the eggs in one zooecium +often vary greatly in size. When mature they reach relatively +considerable dimensions and contain a large amount of food material; but +they are set free from the zooecium as eggs. They lie loose in the +zooecium at a comparatively small size and grow in this position. +Nothing is known as regards the development of _Hislopia_. + +Both forms of the species appear to be confined to water that is free +from all traces of contamination with brine. + + +Order PHYLACTOLAEMATA. + +The polypide in this order possesses a leaf-like ciliated organ (the +epistome) which arises within the lophophore between the mouth and the +anus and projects upwards and forwards over the mouth, which it can be +used to close. The zooecia are never distinct from one another, but in +dendritic forms such as _Plumatella_ the zoarium is divided at irregular +intervals by chitinous partitions. The lophophore in most genera is +horseshoe-shaped instead of circular, the part opposite the anus being +deeply indented. There are no parietal muscles. The orifice of the +zooecium is always circular, and there is no trace of any structure +corresponding to the collar of the ctenostomes. The tentacles are always +webbed at the base. + +All the phylactolaemata produce the peculiar reproductive bodies known as +statoblasts. + +The phylactolaemata, which are probably descended from ctenostomatous +ancestors, are confined to fresh or slightly brackish water. Most of the +genera have a wide geographical distribution, but (with the exception of +a few statoblasts of almost recent date) only one fossil form +(_Plumatellites_, Fric. from the chalk of Bohemia) has been referred to +the order, and that with some doubt. + +It is convenient to recognize two main divisions of the phylactolaemata, +but these divisions hardly merit the distinction of being regarded as +suborders. They may be called Cristatellina and Plumatellina and +distinguished as follows:-- + +Division I, PLUMATELLINA, nov.--Ectocyst well developed; zoaria without +a special organ of progression; polypides contained in tubes. + +Division II, CRISTATELLINA, nov.--Ectocyst absent except at the base of +the zoarium which is modified to form a creeping "sole"; polypides +embedded in a common synoecium of reticulate structure. + +The Cristatellina consist of a single genus and probably of a single +species (_Cristatella mucedo_, Cuvier), which is widely distributed in +Europe and N. America, but has not been found in the Oriental Region. +Eight genera of Plumatellina are known, and five (possibly six) of these +genera occur in India. + + +Division PLUMATELLINA, nov. + +The structure of the species included in this division is very uniform +as regards the internal organs (see fig. 40 opposite and fig. 47 _a_, p. +236). The alimentary canal is simpler than that of the Paludicellidae. A +short oesophagus leads directly into the stomach, the cardiac portion of +which is produced as a vertical limb almost cylindrical in form and not +constricted at the base. This limb is as a rule of greater length than +the oesophagus. The pyloric part of the stomach is elongated and narrow, +and the intestine short, straight, and of ovoid form. There are no cilia +at the pyloric opening. A single funiculus joins the posterior end of +the stomach to the wall of the zooecium, bearing the statoblasts. Sexual +organs are often absent. + +[Illustration: Fig. 40.--Structure of the Plumatellina (after Allman). + +A=a zooecium of _Fredericella_ with the polypide extruded. B=the +lophophore of _Lophopus_ (tentacles removed) as seen obliquely from the +right side. C=larva of _Plumatella_ as seen in optical section. +_a_=tentacles; _b_=velum; _c_=epistome; _d_=mouth; _e_=oesophagus; +_f_=stomach; _g_=intestine; _h_=anus; _j_=retractor muscle; +_k_=parieto-vaginal muscles; _l_=funiculus.] + +Two families may be recognized as constituting the division, _viz._, +(_a_) the Fredericellidae, which have a circular or oval lophophore and +simple statoblast without a swim-ring, and (_b_) the Plumatellidae, in +which the lophophore is shaped like a horseshoe and some or all of the +statoblasts are provided with a ring of air-spaces. + + +Family 1. FREDERICELLIDAE. + + FREDERICELLIDAE, Kraepelin, Deutsch. Suesswasserbryozoen, i, + p. 168 (1887). + +_Zoaria_ dendritic; _zooecia_ distinctly tubular, with the ectocyst well +developed; _statoblasts_ of one kind only, each surrounded by a +chitinous ring devoid of air-spaces; _polypides_ with the lophophore +circular or oval when expanded. + +The Fredericellidae consist of a single genus (_Fredericella_) which +includes several closely-allied forms and has a wide geographical +distribution. + + +Genus FREDERICELLA, _Gervais_ (1838). + + _Fredericella_, Allman, Mon. Fresh-Water Polyzoa, p. 11 + (1857). + + _Plumatella_, ("arret de developpement") Jullien, Bull. Soc. + zool. France, x, p. 121 (1885). + + _Fredericella_, Kraepelin, Deutsch. Suesswasserbryozoen, + i, p. 99 (1887). + + _Fredericella_, Goddard, Proc. Linn. Soc. N. S. Wales, + xxxiv, p. 489 (1909). + +This genus has the characters of the family. Its status has been much +disputed, some authors regarding the shape of the lophophore as of great +morphological importance, while Jullien believed that _Fredericella_ was +merely an abnormal or monstrous form of _Plumatella_. The latter belief +was doubtless due to the fact that the zoaria of the two genera bear a +very close external resemblance to one another and are sometimes found +entangled together. The importance of the shape of the lophophore may, +however, easily be exaggerated, for, as both Jullien and Goddard have +pointed out, it assumes an emarginate form when retracted. + +The best known species is the European and N. American _F. sultana_ +(Blumenbach), of which several varieties or phases have been described +as distinct. This form is stated to occur also in S. Africa. _F. +australiensis_, Goddard[BC] from N. S. Wales is said to differ from this +species in having an oval instead of a circular lophophore and in other +small anatomical characters; but it is doubtful how far these characters +are valid, for the lophophore appears to be capable of changing its +shape to some slight extent and has been stated by Jullien to be +habitually oval in specimens from France. _F. cunningtoni_, +Rousselet[BD] from Lake Tanganyika has stout zooecia encrusted with +relatively large sand-grains. + + [Footnote BC: Proc. Linn. Soc. N. S. Wales, xxxiv, p. 489 + (1909).] + + [Footnote BD: Rousselet, Proc. Zool. Soc. London, 1907 (1), + p. 254.] + +The zoaria of _Fredericella_ are usually found attached to solid objects +in shallow water, but a form described as _F. duplessisi_, Ford has been +found at a depth of 40 fathoms embedded in mud at the bottom of the Lake +of Geneva. _F. cunningtoni_ was dredged from depths of about 10 and +about 25 fathoms. + +The statoblasts of this genus do not float and often germinate in the +parent zooecium after its polypides have died. They are produced in +smaller numbers than is usually the case in other genera of the order. +The polypides sometimes undergo a process of regeneration, but without +the formation of brown bodies. + +[Illustration: Fig. 41.--_Fredericella indica._ + +A=statoblast, x 120. B=outline of expanded lophophore and adjacent +parts, x 75; a=anus, r=rectum. C=outline of zoarium on leaf of +water-plant, x 3. + +(A and B are from specimens from Igatpuri, C from specimen from +Shasthancottah).] + + +28. Fredericella indica, _Annandale_. + + _Fredericella indica_, Annandale, Rec. Ind. Mus. iii, p. 373, + fig. (1909). + + _Fredericella indica_, _id._, _ibid._ v, p. 39 (1910). + +_Zoarium._ The zoarium is of delicate appearance and branches sparingly. +It is often entirely recumbent but sometimes produces short, lax +branches that consist of two or three zooecia only. + +_Zooecia._ The zooecia are very slender and almost cylindrical; they are +slightly emarginate and furrowed, the keel in which the furrow runs +being sometimes prominent. The external surface is minutely roughened +and apparently soft, for small grains of sand and other debris cling to +it, but never thickly. The ectocyst is practically colourless but not +transparent. + +_Statoblasts._ The statoblasts are variable in size and form but most +commonly have a regular broad oval outline; sometimes they are +kidney-shaped. The dorsal surface is covered with minute star-shaped +prominences, which sometimes cover it almost uniformly and are sometimes +more numerous in the centre than towards the periphery. The ventral +surface is smooth. + +_Polypide._ The lophophore bears about 20-25 tentacles, which are very +slender and of moderate length; the velum at their base is narrow; as a +rule the lophophore is accurately circular. + +TYPE in the Indian Museum. + +The most definite character in which this species differs from _F. +sultana_ and _F. australiensis_ is the ornamentation of one surface of +the statoblast, both surfaces of which are smooth in the two latter +species. From _F. cunningtoni_, the statoblasts of which are unknown, it +differs in having almost cylindrical instead of depressed zooecia and in +not having the zooecia densely covered with sand-grains. + +GEOGRAPHICAL DISTRIBUTION.--Western India (the Malabar Zone): Igatpuri +Lake, W. Ghats (alt. ca. 2,000 feet), Bombay Presidency, and +Shasthancottah Lake near Quilon, Travancore. + +BIOLOGY.--In both the lakes in which the species has yet been found it +was collected in November. The specimens obtained in Travancore were +found to be undergoing a process of regeneration due at least partly to +the fact that most of the polypides had perished and that statoblasts +were germinating in the old zooecia. Specimens from the Bombay +Presidency, which were obtained a little later in the month, were in a +more vigorous condition, although even they contained many young +polypides that were not yet fully formed. It seems, therefore, not +improbable that _F. indica_ dies down at the beginning of the hot +weather and is regenerated by the germination of its statoblasts at the +beginning of the cold weather. + +At Shasthancottah zoaria were found entangled with zoaria of a delicate +form of _Plumatella fruticosa_ to which they bore a very close external +resemblance. + + +Family 2. PLUMATELLIDAE. + + PLUMATELLIDAE, Allman (_partim_), Mon. Fresh-Water Polyzoa, + pp. 76, 81 (1857). + +Phylactolaemata which have horseshoe-shaped lophophores and a +well-developed ectocyst not specialized to form an organ of progression. +Some or all of the statoblasts are provided with a "swim-ring" +consisting of symmetrically disposed, polygonal chitinous chambers +containing air. + +It is convenient to divide the Plumatellidae as thus defined into +subfamilies (the Plumatellinae and the Lophopinae), which may be defined +as follows:-- + + +Subfamily A. PLUMATELLINAE. + +Zoarium dendritic or linear, firmly fixed to extraneous objects; zooecia +tubular, not fused together to form a gelatinous mass. + + +Subfamily B. LOPHOPINAE. + +Zoarium forming a gelatinous mass in which the tubular nature of the +zooecia almost disappears, capable to a limited extent of progression +along a smooth surface. + +Both these subfamilies are represented in the Indian fauna, the +Plumatellinae by two of the three genera known to exist, and the +Lophopinae by two (or possibly three) of the four that have been +described. The following key includes all the known genera, but the +names of those that have not been recorded from India are enclosed in +square brackets. + + +_Key to the Genera of_ Plumatellidae. + + I. Statoblasts without marginal processes. + A. Zooecia cylindrical, not embedded in a gelatinous + investment (Plumatellinae). + _a_. Zooecia arising directly from one another; + no stolon; free statoblast oval PLUMATELLA, p. 212. + _a'_. Zooecia arising singly or in groups from + an adherent stolon; free statoblasts oval. STOLELLA, p. 229. + B. Zooecia cylindrical, embedded in a structureless + gelatinous investment. + Zooecia arising from a ramifying stolon; + statoblasts circular [STEPHANELLA.] + C. Polypides embedded in a hyaline synoecium + that conceals the cylindrical form of the + zooecia (Lophopinae). + _c_. Polypides upright, their base far removed + from that of the zoarium when they are + expanded LOPHOPUS, p. 231. + _c'_. Polypides recumbent for the greater + part of their length at the base of + the zoarium [AUSTRALELLA[BE].] + II. Statoblasts armed (normally) with hooked + processes (Lophopinae). + A. Processes confined to the extremities of + the statoblast; zoaria remaining separate + throughout life LOPHOPODELLA, p. 231. + B. Processes entirely surrounding the + statoblast; many zoaria embedded in a + common gelatinous investment so as to + form large compound colonies PECTINATELLA, p. 235. + + [Footnote BE: See Rec. Ind. Mus. v, p. 40, footnote (1910).] + + +Subfamily A. PLUMATELLINAE. + +Of the two Indian genera of this subfamily, one (_Plumatella_) is almost +universally distributed, while the other (_Stolella_) has only been +found in the valley of the Ganges. The third genus of the subfamily +(_Stephanella_) is only known from Japan. + +It should be noted that zoaria of different species and genera of this +subfamily are often found in close proximity to one another and to +zoaria of _Fredericella_, and that the branches of the different species +are sometimes entangled together in such a way that they appear, unless +carefully separated, to belong to the same zoarium. + + +Genus 1. PLUMATELLA, _Lamarck_. + + _Plumatella_, Lamarck, Animaux sans Vert. (ed. 1re) ii, p. + 106 (1816). + + _Alcyonella_, _id_., _ibid_. p. 100. + + _Plumatella_, Allman, Mon. Fresh-Water Polyzoa, p. 92 + (1857). + + _Alcyonella_, _id_., _ibid_. p. 86. + + _Plumatella_, Hyatt, Comm. Essex Inst. iv, p. 207, pl. viii + (1866). + + _Plumatella_, Jullien (_partim_), Bull. Soc. zool. France, + x, p. 100 (1885). + + _Hyalinella_, _id_., _ibid_. p. 133. + + _Plumatella_, Kraepelin, Deutsch. Suesswass. Bryozoen, i, p. + 104 (1887). + + _Plumatella_, Braem, Unter. ue. Bryozoen des suessen Wassers, + p. 2 (Bibliotheca Zoologica, ii, 1890). + +_Zoarium_ dendritic, recumbent, erect, or partly recumbent and partly +erect. + +_Zooecia_ tubular, not confined in a gelatinous synoecium; the ectocyst +usually horny. + +_Statoblasts_ often of two kinds, free and stationary, the latter +without air-cells and as a rule adherent by one surface, the former +provided with a well-developed ring of air-cells but without marginal +processes, oval in form, never more than about 0.6 mm. in length. + +_Polypide_ with less than 65 tentacles. + +[Illustration: Fig. 42.--Outlines of free statoblasts of _Plumatella_ +(enlarged). + +A, of _P. fruticosa_ (Calcutta); B, of _P. emarginata_ (Calcutta); C, of +_P. javanica_ (Travancore); D, of _P. diffusa_ (Sikhim); E, of _P. +allmani_ (Bhim Tal); F, of _P. diffusa_ (Rajshahi, Bengal); G, G', of +_P. punctata_ (Calcutta); H, of _P. diffusa_ (Sikhim), statoblast +further enlarged: A=outline of capsule; B=limit of swim-ring on +ventral surface; C=limit of swim-ring on dorsal surface. [The dark +area represents the capsule of the statoblast.]] + +Certain forms of this genus are liable to become compacted together in +such a way as to constitute solid masses consisting of elongate vertical +zooecia closely parallel to one another and sometimes agglutinated by +means of a gummy substance. These forms were given by Lamarck in 1816 +the name _Alcyonella_, and there has been much dispute as to whether +they represent a distinct genus, distinct species, or merely varieties +or phases of more typical forms. It appears to be the case that all +species which produce vertical branches are liable to have these +branches closely packed together and the individual zooecia of which +they are composed more or less greatly elongated. It is in this way that +the form known to Allman as _Alcyonella benedeni_ is produced from the +typical _Plumatella emarginata_. Other forms go further and secrete a +gummy substance that glues the upright zooecia together and forces them +to elongate themselves without branching. In these conditions the +zooecia become polygonal in cross-section. It is probable that such +forms (_e. g._, _Plumatella fungosa_ (Pallas)) should rank as distinct +species, for the gummy secretion is present in great profusion even in +young zoaria in which the zooecia have not yet assumed a vertical +position. No such form, however, has as yet been found in India, and in +any case it is impossible to regard _Alcyonella_ as a distinct genus. + + + _Key to the Indian Species of_ Plumatella. + + I. Ectocyst more or less stiff, capable of + transverse wrinkling only near the tips of + the zooecia, never contractile or greatly + swollen; zooecia rounded[BF] at the tip when + the polypide is retracted. Free statoblasts + elongate; the free portion of their swim-ring + distinctly narrower at the sides than at + the ends. + A. Ectocyst by no means rigid, of a uniform + pale colour; zooecia never emarginate or + furrowed, straight, curved or sinuous, + elongate, cylindrical _fruticosa_, p. 217. + B. Ectocyst rigid; zooecia (or at any rate + some of the zooecia) emarginate and furrowed. + _b_. Ectocyst darkly pigmented over the + greater part of each zooecium, white + at the tip; branching of the zoarium + practically dichotomous, profuse, as + a rule both horizontal and vertical; + zooecia straight or slightly curved + or sinuous _emarginata_, p. 220. + _b'_. Ectocyst colourless and hyaline; + branching of the zoarium sparse, + lateral, irregular, horizontal; + zooecia nearly straight, strongly + emarginate and furrowed _javanica_, p. 221. + _b''_. The majority of the zooecia distinctly + L-shaped, one limb being as a rule + adherent; ectocyst never densely + pigmented. + beta. Zooecia cylindrical, their furrowed + keel never prominent _diffusa_, p. 223. + beta'. Zooecia (or at any rate some of the + zooecia) constricted or tapering at + the base, their emargination and + furrow conspicuous _allmani_, p. 224. + + II. Ectocyst stiff; zooecia truncated when the + polypide is retracted. Surface of zooecia + minutely roughened, distinctly annulate on + the distal part _tanganyikae_, p. 225. + III. Ectocyst swollen and contractile, capable + of transverse wrinkling all over the + zooecium; zooecia never emarginate _punctata_, p. 227. + + [Footnote BF: In specimens preserved in spirit they are apt + to collapse and therefore to become somewhat concave.] + +There has always been much difficulty in separating the species of +_Plumatella_, and even now there is no general consensus of opinion as +to the number that should be recognized. The difficulty, however, is +much reduced if the following precautions are observed:-- + + (1) If the zoarium appears to be tangled, if the branches + intertwine or overlap, or if the zooecia are closely pressed + together, the whole mass should be carefully dissected out. + This is necessary not only because zoaria belonging to + different species are sometimes found entangled together but + also because it is often difficult to recognize the + characteristic method of branching and shape of the zooecia + unless it is done. + + (2) As large a part as possible of each zoarium should be + examined, preferably with a binocular microscope, and + allowance should be made for irregularities and + abnormalities of all kinds. What must be observed is the + rule rather than the exceptions. + + (3) When the statoblasts are being examined, care must be + taken that they lie flat and that their surface is parallel + to that of the nose-piece of the microscope. If they are + viewed obliquely it is impossible to see their true outlines + and proportions. + + (4) In order to see the relative proportions of the capsule + and the swim-ring it is necessary that the statoblast should + be rendered transparent. This is often difficult owing to + the presence of air in the air-cells, but strong nitric acid + applied judiciously will render it possible (p. 240). + +In supervising the preparation of the plates that illustrate this genus +I have impressed upon the artist the importance of representing what he +saw rather than what he thought he ought to see, and the figures are +very close copies of actual specimens. I have deliberately chosen for +representation specimens of _Plumatella_ preserved by the simple methods +which are often the only ones that it is possible for a traveller to +adopt, for the great majority of naturalists will probably have no +opportunity of examining living specimens or specimens preserved by +special methods, and the main object, I take it, of this series is to +enable naturalists first to distinguish the species described and then +to learn something of their habitat and habits. + +GEOGRAPHICAL DISTRIBUTION.--Of the seven species included in this key +five have been found in Europe (namely _P. fruticosa_, _P. emarginata_, +_P. diffusa_, _P. allmani_, and _P. punctata_), while of these five all +but _P. allmani_ are known to occur in N. America also. _P. javanica_ is +apparently peculiar to the Oriental Region, while _P. tanganyikae_ has +only been taken in Central Africa and in the Bombay Presidency. + +TYPES.--Very few of the type-specimens of the older species of +_Plumatella_ are in existence. Allman's are neither in Edinburgh nor in +London, and Mr. E. Leonard Gill, who has been kind enough to go through +the Hancock Collection at Newcastle-on-Tyne, tells me that he cannot +trace Hancock's. Those of the forms described by Kraepelin are in +Hamburg and that of _P. tanganyikae_ in the British Museum, and there are +schizotypes or paratypes of this species and of _P. javanica_ in +Calcutta. The types of Leidy's species were at one time in the +collection of the Philadelphia Academy of Science. + +BIOLOGY.--The zoaria of the species of _Plumatella_ are found firmly +attached to stones, bricks, logs of wood, sticks, floating seeds, the +stems and roots of water-plants, and occasionally to the shells of +molluscs such as _Vivipara_ and _Unio_. Some species shun the light, but +all are apparently confined to shallow water. + +Various small oligochaete worms (e. g., _Chaetogaster spongillae_,[BG] +_Nais obtusa_, _Nais elinguis_, _Slavina appendiculata_ and _Pristina +longiseta_[BH]), take shelter amongst them; dipterous larvae of the genus +_Chironomus_ often build their protective tubes at the base of the +zoaria, and the surface of the zooecia commonly bears a more or less +profuse growth of such protozoa as _Vorticella_ and _Epistylis_. I have +seen a worm of the genus _Chaetogaster_ devouring the tentacles of a +polypide that had been accidentally injured, but as a rule the movements +of the lophophore are too quick to permit attacks of the kind, and I +know of no active enemy of the genus. The growth of sponges at the base +of the zoaria probably chokes some species, but one form (_F. +fruticosa_) is able to surmount this difficulty by elongating its +zooecia (p. 219). A small worm (_Aulophorus tonkinensis_) which is +common in ponds in Burma and the east of India as far west as Lucknow, +often builds the tube in which it lives mainly of the free statoblasts +of this genus. It apparently makes no selection in so doing but merely +gathers the commonest and lightest objects it can find, for small seeds +and minute fragments of wood as well as sponge gemmules and statoblasts +of other genera are also collected by it. I know of no better way of +obtaining a general idea as to what sponges and phylactolaemata are +present in a pond than to examine the tubes of _Aulophorus tonkinensis_. + + [Footnote BG: Annandale, J. As. Soc. Bengal (n. s.) ii, p. + 188, pl. i (1906).] + + [Footnote BH: See Michaelsen, Mem. Ind. Mus. i, pp. 131-135 + (1908).] + +I am indebted to Mr. F. H. Gravely, Assistant Superintendent in the +Indian Museum, for an interesting note regarding the food of +_Plumatella_. His observations, which were made in Northamptonshire, +were unfortunately interrupted at a critical moment, but I have +reproduced them with his consent in order that other observers may +investigate the phenomena he saw. Mr. Gravely noted that a small green +flagellate which was abundant in water in which _Plumatella repens_ was +growing luxuriantly, was swallowed by the polypides, and that if the +polyparium was kept in a shallow dish of water, living flagellata of the +same species congregated in a little pile under the anus of each +polypide. His preparations show very clearly that the flagellates were +passing through the alimentary canal without apparent change, but the +method of preservation does not permit the retractile granules, which +were present in large numbers in the cell-substance of the flagellates, +to be displayed and it is possible that these granules had disappeared +from those flagellates which are present in the recta of his specimens. +It is clear, therefore, either that certain flagellates must pass +through the alimentary canal of _Plumatella_ unchanged, or that the +polyzoon must have the power of absorbing the stored food material the +flagellates contain without doing them any other injury. + +The free statoblasts of _Plumatella_ are as a rule set free before the +cells they contain become differentiated, and float on the surface of +the water for some time before they germinate; but occasionally a small +polypide is formed inside the capsule while it is still in its parent +zooecium. I have, however, seen only one instance of this premature +development, in a single statoblast contained in a small zoarium of _P. +fruticosa_ found in Lower Burma in March. The fixed statoblasts usually +remain fixed to the support of the zoarium, even when their +parent-zooecium decays, and germinate _in situ_. + +The larva (fig. 40 C, p. 207) that originates from the egg of +_Plumatella_ is a minute pear-shaped, bladder-like body covered +externally with fine vibratile threads (cilia) and having a pore at the +narrow end. At the period at which it is set free from the parent +zooecium it already contains a fully formed polypide or pair of +polypides with the tentacles directed towards the narrow end. After a +brief period of active life, during which it moves through the water by +means of its cilia, it settles down on its broad end, which becomes +adhesive; the polypide or pair of polypides is everted through the pore +at the narrow end, the whole of this end is turned inside out, and a +fresh polyparium is rapidly formed by budding. + + +29. Plumatella fruticosa, _Allman_. (Plate III, fig. 1; plate IV, fig. +4; plate V, fig. 1.) + + _Plumatella fruticosa_, Allman, Ann. Nat. Hist. xiii, p. 331 + (1844). + + _Plumatella repens_, van Beneden (? _nec_ Linne), Mem. Acad. + Roy. Belg. 1847, p. 21, pl. i, figs. 1-4. + + _Plumatella fruticosa_, Johnston, Brit. Zooph. (ed. 2), p. + 404 (1847). + + _Plumatella coralloides_, Allman, Rep. Brit. Assoc. 1850, p. + 335. + + _Plumatella stricta_, _id._, Mon. Fresh-Water Polyzoa, p. + 99, fig. 14 (1857). + + _Plumatella fruticosa_, _id._, _ibid._ p. 102, pl. vi, figs. + 3-5. + + _Plumatella coralloides_, _id._, _ibid._ p. 103, pl. vii, + figs. 1-4. + + _Plumatella repens_ and _P. stricta_, Carter, Ann. Nat. + Hist. (3) iii, p. 341 (1859). + + _Plumatella lucifuga_, Jullien (_partim_), Bull. Soc. zool. + France, x, p. 114 (1885). + + _Plumatella princeps_ var. _fruticosa_, Kraepelin, Deutsch. + Suesswasserbryozoen, i, p. 120, pl. vii, fig. 148 (1887). + + _Plumatella fruticosa_, Braem, Unter. ii. Bryozoen des + suessen Wassers, p. 9, pl. i, fig. 15 (Bibl. Zool. ii) + (1890). + + _Plumatella repens_, Annandale, J. As. Soc. Bengal (new + series) iii, 1907, p. 88. + + _Plumatella emarginata_, Loppens (_partim_), Ann. Biol. + lacustre, iii, p. 161 (1908). + + _Plumatella fruticosa_, Annandale, Rec. Ind. Mus. v, p. 45 + (1910). + +_Zoarium._ The zoarium in the typical form has a loose appearance due to +the fact that the branches are far apart and the ectocyst by no means +rigid. When young the zoarium is adherent, but in well-grown polyparia +vertical branches, often an inch or more in length, are freely produced. +As a rule they have not the strength to stand upright if removed from +the water. Branching is ordinarily lateral and as a rule occurs chiefly +on one side of a main branch or trunk. In certain circumstances upright +zooecia are pressed together and reach a great length without branching, +and in this form (_P. coralloides_, Allman) daughter-zooecia are often +produced at the tip of an elongated mother-zooecium in fan-like +formation. A depauperated form (_P. stricta_, Allman), occurs in which +the vertical branches are absent or very short. In all forms internal +partitions are numerous and stout. + +_Zooecia._ The zooecia are cylindrical and bear a simple keel on their +dorsal surface. They are never emarginate or furrowed. In the typical +form their diameter is more than half a millimetre, and they are always +of considerable length. The ectocyst is thin and never very rigid or +deeply pigmented, the colour usually being an almost uniform pale +pinkish brown and fading little towards the tip of the zooecium. + +_Statoblasts._ Both free and stationary statoblasts are formed, but the +latter are rare and do not always adhere. They resemble the free +statoblasts in general form but have a solid margin instead of a +swim-ring and are often minutely serrated round the edge. The free +statoblasts are at least considerably, sometimes very elongate; in all +zoaria it is possible to find specimens that are more than twice as long +as broad. The capsule is relatively large and resembles the swim-ring in +outline, so that the free portion of the latter is not much narrower at +the sides than at the ends. The sides are distinctly convex and the ends +rounded; the swim-ring encroaches little on the surface of the capsule. + +_Polypide._ The tentacles number between 40 and 50 and are not festooned +at the base. The stomach is slender and elongate. + +TYPE not in existence. + +SYSTEMATIC REMARKS.--_P. fruticosa_ is closely allied to _P. repens_ +(European and N. American) but always has much longer statoblasts. Three +phases of the species may be distinguished as follows:-- + + A. (_Forma typica_). Zooecia stout in form, not greatly + elongate; free branches produced in profusion. + + B. (_P. stricta_, Allman, _P. repens_, van Beneden). Zooecia + slender; free branches absent or consisting of two or three + zooecia only. + + C. (_P. coralloides_, Allman). Vertical zooecia pressed + together and greatly elongated. + +Indian specimens of the typical form agree well with German specimens +labelled by Prof. Kraepelin _P. princeps_ var. _fruticosa_, and +specimens of the _coralloides_ phase could hardly be distinguished from +similar specimens from Scotland. + +GEOGRAPHICAL DISTRIBUTION.--_P. fruticosa_ is widely distributed in +Europe and probably in N. America. I have seen Indian specimens from the +Punjab (Lahore, _Stephenson_), from Bombay, from Travancore, from +Calcutta and other places in the Ganges delta, from Rajshahi (Rampur +Bhoolia) on the R. Ganges, from Kurseong in the E. Himalayas (alt. 4,500 +feet), and from Kawkareik in Tenasserim. Statoblasts found on the +surface of a pond near Simla in the W. Himalayas (alt. _ca._ 8,000 +feet), probably belong to this species. + +BIOLOGY.--Allman states that in England _P. fruticosa_ is fond of still +and slowly-running water. The typical form and the _coralloides_ phase +grow abundantly in the Calcutta tanks, the former often attaining an +extraordinary luxuriance. I have found the var. _stricta_ only in water +in which there was reason to suspect a lack of minute life (and +therefore of food), viz. in Shasthancottah Lake in Travancore, in a +swamp in Lower Burma, and in a small jungle stream near the base of the +Western Ghats in Travancore. The species is the only one that I have +seen in running water in India, and the specimens obtained in the jungle +stream in Travancore are the only specimens I have taken in these +circumstances. _P. fruticosa_ always grows near the surface or near the +edge of water; it is found attached to the stems of bulrushes and other +aquatic plants, to floating seeds and logs and (rarely) to stones and +bricks. So far as my experience goes it is only found, at any rate in +Calcutta, in the cold weather and does not make its appearance earlier +than October. + +The form Allman called _P. coralloides_ was found by him, "attached to +floating logs of wood, together with _P. repens_ and _Cordylophora +lacustris_, and generally immersed in masses of _Spongilla +fluviatilis_." I have always found it immersed in sponges (_S. +lacustris_, _S. alba_, _S. carteri_, and _S. crassissima_), except when +the sponge in which it had been immersed had decayed. Indeed, the +peculiar form it has assumed appears to be directly due to the pressure +of the growing sponge exerted on the zooecia, for it is often possible +to find a zoarium that has been partially overgrown by a sponge and has +retained its typical form so long as it was free but has assumed the +_coralloides_ form where immersed.[BI] In Shasthancottah Lake, +Travancore, I found specimens of the _stricta_ phase embedded in the +gelatinous mass formed by a social rotifer and to some extent +assimilated to the _coralloides_ form. + + [Footnote BI: Braem (_op. cit._, p. 3, pl. i, fig. 1), has + described and figured under the name _P. fungosa_ var. + _coralloides_, Allman, a dense form that somewhat resembles + this phase of _P. fruticosa_ but has become compacted + without external pressure. It is, however, probably a form + of _P. repens_ rather than _P. fungosa_ and differs in its + broad statoblasts from any form of _P. fruticosa_. I have + examined specimens of the same form from England.] + + +30. Plumatella emarginata, _Allman_. (Plate III, fig. 2; plate IV, figs. +1, 1 _a._) + + _Plumatella emarginata_, Allman, Ann. Nat. Hist. xiii, p. + 330 (1844). + + _Plumatella emarginata_, Johnston, Brit. Zooph. (ed. 2), p. + 404 (1847). + + _Alcyonella benedeni_, Allman, Mon. Fresh-Water Polyzoa, p. + 89, pl. iv, figs. 5-11 (1857). + + _Plumatella emarginata_, _id._, _ibid._ p. 104, pl. vii, + figs. 5-10. + + _Plumatella lucifuga_, Jullien, Bull. Soc. zool. France, x, + figs. 89, 90, p. 114 (1885). + + _Plumatella princeps_ var. _emarginata_, Kraepelin + (_partim_), Deutsch. Suesswasserbryoz. p. 120, pl. iv, fig. + 108, pl. v, fig. 123 (1887). + + _Plumatella emarginata_, Braem, Unter. ii. Bryoz. suessen + Wassers, p. 9, pl. i, figs. 12, 14 (Bibl. Zool. ii) (1890). + + _Plumatella emarginata_, Annandale (_partim_), J. As. Soc. + Bengal, (new series) iii, 1907, p. 89. + + _Plumatella princeps_, Loppens (_partim_), Ann. Biol. + lacustre, iii, p. 162, fig. 7 (1908). + + _Plumatella emarginata_, Annandale, Rec. Ind. Mus. v, p. 47 + (1910). + +_Zoarium._ The zoarium often covers a considerable area on flat surfaces +and is sometimes entirely recumbent. More usually, however, the younger +part is vertical. In either case the branching is practically +dichotomous, two young zooecia arising almost simultaneously at the tip +of a mother-zooecium and diverging from one another at a small angle. +When the zoarium becomes vertical, rigid branches of as much as an inch +in length are sometimes produced in this way and, arising parallel to +one another, are pressed together to form an almost solid mass +(=_Alcyonella benedeni_, Allman). In such cases the basal zooecium or at +any rate the basal part of each upright branch is considerably +elongated. In recumbent zooecia the main branches often radiate outwards +from a common centre. + +_Zooecia._ The zooecia are of almost equal width throughout, slender, +and moderately elongate when recumbent. Their ectocyst is stiff; they +are emarginate at the tip and more or less distinctly furrowed on the +dorsal surface, the keel in which the furrow runs not being prominent. +The orifice is often on the dorsal surface even in upright branches. +Each zooecium is of a dark brown or almost black colour for the greater +part of its length but has a conspicuous white tip which is extended +down the dorsal surface in the form of a triangle, its limits being +rather more extensive than and parallel to those of the emargination. + +_Statoblast._ The majority of the free statoblasts are elongate and +truncate or subtruncate at the extremities, the sides being as a rule +straight and parallel. In every polyparium specimens will be found that +are between twice and thrice as long as broad. The capsule is, however, +relatively much broader than the swim-ring, often being nearly circular, +and there is therefore at either end a considerable extent of free +air-cells, while the extent of these cells at the sides of the capsule +is small. The air-cells cover a considerable part of the dorsal surface +of the capsule. Fixed statoblasts are usually found in old colonies, +especially at the approach of the hot weather. They have an oval form +and are surrounded by a membranous margin on which traces of +reticulation can often be detected. As a rule statoblasts of both types +are produced in considerable but not in excessive numbers. + +_Polypide._ There are about 40 tentacles, the velum at the base of which +extends upwards for a considerable distance without being festooned. The +stomach is elongate and slender and narrowly rounded at the base. + +The method of branching, the coloration of the zooecia and the form of +the free statoblast are all characteristic. Luxuriant or closely +compressed zoaria of _P. diffusa_ often bear a superficial resemblance +to those of _P. emarginata_, but the resemblance disappears if they are +carefully dissected out. Indian specimens of _P. emarginata_ agree +closely with European ones. + +GEOGRAPHICAL DISTRIBUTION.--_P. emarginata_ is a common species in +Europe, N. America, and southern Asia and probably also occurs in Africa +and Australia. I have examined specimens from Calcutta, Rangoon, and +Mandalay in Indian territory, and also from Jalor in the Patani States +(Malay Peninsula) and the Tale Noi, Lakon Sitamarat, Lower Siam. +Gemmules found by Apstein (Zool. Jahrb. (Syst.) xxv, 1907, p. 201) in +plankton from the Colombo lake may belong to this species or to any of +the others included by Kraepelin in his _P. princeps_. + +BIOLOGY.--In Ireland Allan found _P. emarginata_ in streams and +rivulets, but it also occurs in European lakes. In India I have only +found it in ponds. It prefers to adhere to the surface of stones or +bricks, but when these are not available is found on the stems of +water-plants. In the latter position the form called _Alcyonella +benedeni_ by Allman is usually produced, owing to the fact that the +upright branches are crowded together through lack of space, very much +in the same way (although owing to a different cause) as those of _P. +fruticosa_ are crowded together in the _coralloides_ phase, to which the +_benedeni_ phase of _P. emarginata_ is in many respects analogous. + +Although it is essentially a cold-weather species in Calcutta, _P. +emarginata_ is sometimes found in a living condition during the "rains." +Zoaria examined at this season, however, contains few living polypides, +the majority of the zooecia having rotted away and left fixed +statoblasts only to mark their former position. + + +31. Plumatella javanica, _Kraepelin_. + + _Plumatella javanica_, Kraepelin, Mitt. Nat. Mus. Hamb. + xxiii, p. 143, figs. 1-3 (1903). + + _Plumatella emarginata_ var. _javanica_, Loppens, Ann. Biol. + lacustre, iii, p. 162 (1908). + + _Plumatella javanica_, Annandale, Rec. Ind. Mus. v, p. 50 + (1910). + + _Plumatella allmani_ var. _dumortieri_, _id._ (_partim_) + (_nec_ Allman), _ibid._ p. 49. + +This species is related to _P. emarginata_, from which it may be +distinguished by the following characters:-- + +_Zoarium._ The zoarium is always entirely recumbent and branches +sparingly; its method of branching does not approach the dichotomous +type but is lateral and irregular. Linear series of zooecia without +lateral branches are often formed. + +_Zooecia._ The zooecia are slender and often very long; they are +strongly emarginate and furrowed, and the keel that contains the furrow +is conspicuous. The ectocyst is hyaline and as a rule absolutely +colourless. + +_Statoblasts._ The free statoblasts are variable in length, sometimes +distinctly elongate, sometimes elongate only to a moderate degree; they +are rounded at the extremities and have the sides slightly or distinctly +convex outwards. The capsule is relatively large, and the free portion +of the swim-ring is not much broader at the ends than at the sides. The +fixed statoblasts are elongate and surrounded by an irregularly shaped +chitinous membrane, which is often of considerable extent. The whole of +the dorsal surface is covered with what appear to be rudimentary +air-spaces some of which even contain air. + +The transparent glassy ectocyst and strong furrowed keel of this species +are very characteristic, but the former character is apt to be obscured +by staining due to external causes, especially when the zoarium is +attached to dead wood. The shape of the free statoblasts is too variable +to be regarded as a good diagnostic character, but the fixed +statoblasts, when they are to be found, are very characteristic in +appearance. _P. javanica_ appears to be closely related to Allman's _P. +dumortieri_, with which stained zoaria are apt to be confused. The +character of the ectocyst is, however, different, and the free part of +the swim-ring is distinctly narrower at the sides of the free +statoblasts. Dr. Kraepelin has been kind enough to send me one of the +types. + +TYPES in the Hamburg and Indian Museums. + +GEOGRAPHICAL DISTRIBUTION.--Java, Penang, India. Indian localities +are:--BENGAL, Calcutta; Berhampore, Murshidabad; R. Jharai, Siripur, +Saran district, Tirhut: E. HIMALAYAS, Kurseong, Darjiling district (alt. +4,500 feet): MADRAS PRESIDENCY, canal near Srayikaad, Travancore. Mr. C. +W. Beebe has recently sent me a specimen taken by him in the Botanical +Gardens at Penang. + +BIOLOGY.--Very little is known about the biology of this species. +Kraepelin took it in Java on the leaves of water-lilies. It is not +uncommon during the cold weather in the Calcutta Zoological Gardens on +floating seeds and sticks and on the stems of bulrushes; in Travancore I +took it in November on the submerged leaves of _Pandani_ growing at the +edge of a canal of slightly brackish water. Mr. Hodgart, the collector +of the Indian Museum, found it in the R. Jharai on the stems of +water-plants at a time of flood in the "rains." In Calcutta it is often +found entangled with _P. fruticosa_ and _P. emarginata_. + + +32. Plumatella diffusa, _Leidy_. (Plate IV, fig. 2.) + + _Plumatella diffusa_, Leidy, P. Ac. Philad. v, p. 261 + (1852). + + _Plumatella diffusa_, Allman, Mon. Fresh-Water Polyzoa, p. + 105 (1857). + + _Plumatella diffusa_, Hyatt, Comm. Essex Inst. iv, pl. viii, + figs. 11, 12 (1866). + + _Plumatella diffusa_, _id._, _ibid._ v, p. 107, fig. 12 + (1868). + + _Plumatella repens_, Jullien, Bull. Soc. zool. France, x, + fig. 37 (_lapsus_ for 73), p. 110 (1885). + + _Plumatella diffusa_, _id._, _ibid._ figs. 155, 157, pp. + 130, 131. + + _Plumatella allmani_ var. _diffusa_, Annandale, Rec. Ind. + Mus. v, p. 49 (1910). + +_Zoarium._ The zoarium often covers a considerable area on flat surfaces +and is sometimes found crowded together on the stems of plants. In the +latter case the arrangement of the main branches is distinctly radiate. +Upright branches occur rarely and never consist of more than three +zooecia. The characteristic method of branching is best represented by +the following diagram:-- + +[Illustration: Fig. 43.] + +The partitions are stout and numerous. + +_Zooecia._ The great majority of the zooecia in each zoarium are +distinctly L-shaped, the long limb being usually adherent. The vital +organs of the polypide are contained in the vertical limb, while the +horizontal one, in mature polyparia, is packed full of free statoblasts. +The zooecia are cylindrical and as a rule obscurely emarginate and +furrowed. The ectocyst is stiff; it is never deeply pigmented but is +usually of a transparent horn-colour at the base of each zooecium and +colourless at the tip, the contrast between the two portions never being +very strong. The basal portion is rough on the surface, the distal +portion smooth. + +_Statoblasts._ Free statoblasts are produced in very great profusion and +fixed statoblasts are also to be found as a rule. The latter resemble +those of _P. emarginata_. The free statoblasts are never very large or +relatively broad, but they vary considerably as regards size and +outline. The capsule is large, the sides convex outwards and the +extremity more or less broadly rounded. The air-cells are unusually +large and extend over a great part of the dorsal surface of the +statoblast. + +_Polypide._ The polypide is shorter and stouter than that of _P. +emarginata_ and as a rule has fewer tentacles. + +The most characteristic feature of this species is the form of the +zooecia, which differ greatly from those of any other Indian species but +_P. allmani_. In the latter they are distinctly "keg-shaped" (_i. e._, +constricted at the base and swollen in the middle), and the zoarium +never spreads out over large surfaces in the way in which that of _P. +diffusa_ does. + +TYPE--? in the Philadelphia Academy of Sciences. + +GEOGRAPHICAL DISTRIBUTION.--This species was originally described from +North America (in which it is apparently common) and occurs also in +Europe. I have seen Indian specimens from the following +localities:--BENGAL, Calcutta and neighbourhood; Rajshahi (Rampur +Bhulia): E. HIMALAYAS, Gangtok, Native Sikhim (alt. 6,150 feet) +(_Kirkpatrick_, _Stewart_): PUNJAB, Lahore (_Stephenson_). + +BIOLOGY.--_P. diffusa_ in Lower Bengal is a cold-weather species. It is +remarkable for the enormous number of gemmules it produces and is +usually found either on floating objects such as the stems of certain +water-plants, or on stones or bricks at the edge of ponds. + + +33. Plumatella allmani, _Hancock_. (Plate IV, figs. 3, 3 _a_.) + + _Plumatella allmani_, Hancock, Ann. Nat. Hist. (2) v, p. + 200, pl. v, fig. 3-4, pl. iii, fig. 2-3 (1850). + + _Plumatella allmani_, Allman, Mon. Fresh-Water Polyzoa, p. + 106, fig. 16 (1857). + + _Plumatella elegans_, _id._, _ibid._ p. 107, pl. viii, figs. + 6-10. + + _Plumatella lucifuga_ ("forme rampante") Jullien, Bull. Soc. + zool. France, x, p. 114 (1885). + +This species is closely allied to _P. diffusa_, from which it differs in +the following characters:-- + + (1) The zoarium never covers a large area and as a rule + grows sparingly and mainly in two directions. + + (2) The zooecia are more irregular in shape, not so + distinctly elbowed, smaller; they have a much more + prominently keeled ridge. The great majority of them are + constricted at the base and taper towards the orifice. In + young zoaria they are almost colourless but in older ones + there is a band of not very dense pigment round the base of + the vertical limb. + + (3) The free statoblasts are comparatively large and usually + show a tendency to taper at the extremities, often being + almost rhomboidal in form. The swim-ring does not extend so + far over the dorsal surface as it does in those of _P. + diffusa_; the "cells" of which it is composed are small. + +TYPE not in existence. + +I have seen every gradation between this form and Allman's _P. elegans_. + +GEOGRAPHICAL DISTRIBUTION.--_P. allmani_ is apparently a rare species to +which there are few references in literature. It was originally +described from England and is stated by Jullien to occur in France. I +have found specimens only in the lake Bhim Tal (alt. 4,500 feet) in the +W. Himalayas. + +BIOLOGY.--The original specimens were found by Hancock on stones. My own +were growing on the leaves of water-plants, usually on the under side. +When the zooecia were forced to stretch across from one leaflet to +another they assumed the sinuous form characteristic of Allman's _P. +elegans_. + + +34. Plumatella tanganyikae, _Rousselet_. + + _Plumatella tanganyikae_, Rousselet, Proc. Zool. Soc. London, + 1907 (i), p. 252, pl. xiv, figs. 1-4. + + _Plumatella bombayensis_, Annandale, Rec. Ind. Mus. ii, p. + 169, figs. 1, 2 (1908). + + _Plumatella bombayensis_, _id._, _ibid._ v, p. 51 (1910). + +_Zoarium._ The whole colony is recumbent but branches freely and at +short intervals in a horizontal plane, so that the zooecia become +crowded together and the branches sometimes overlap one another. The +zoarium often covers a considerable area, but growth seems to be mainly +in two directions. When growing on the stems of water-plants the +branches are often parallel and closely pressed together but remain +recumbent in this position. A stout membrane sometimes extends between +branches and individual zooecia. + +_Zooecia._ The walls of the zooecia are thick, stiff, and more or less +darkly but not opaquely pigmented; the external surface, although not +very smooth, is always clean. The two most noteworthy characters of the +zooecia are (i) their truncated appearance when the polypide is +retracted, and (ii) the conspicuous, although often irregular external +annulation of their walls. The tip of each zooecium, owing to the fact +that the invaginated part of the ectocyst is soft and sharply separated +from the stiffened wall of the tube, terminates abruptly and is not +rounded off gradually as is the case in most species of the genus; +sometimes it expands into a trumpet-like mouth. The annulation of the +external surface is due to numerous thickened areas of the ectocyst +which take the form of slender rings surrounding the zooecium; they are +most conspicuous on its distal half. On the dorsal surface of the base +of each zooecium there is a conspicuous furrowed keel, which, however, +does not usually extend to the distal end; the latter is oval in +cross-section. The zooecia are short and broad; their base is always +recumbent, and, when the zoarium is attached to a stone or shell, often +seems to be actually embedded in the support; the distal part turns +upwards and is free, so that the aperture is terminal; the zooecia of +the older parts of the zoarium exhibit the specific characters much more +clearly than those at the growing points. + +_Polypide._ The lophophore bears 20 to 30 tentacles, which are long and +slender; the velum at their base extends up each tentacle in the form of +a sharply pointed projection, but these projections do not extend for +more than one-fifth of the length of the tentacles. Both the velum and +the tentacular sheath bear numerous minute tubercles on the external +surface. The base of the stomach is rounded, and the whole of the +alimentary canal has a stout appearance. + +[Illustration: Fig. 44.--_Plumatella tanganyikae_ from Igatpuri Lake. + +A=outline of part of zoarium from a stone, x 16; B=outline of the tip of +a single zooecium, x 70; C=free statoblast, x 70.] + +_Statoblasts._ Both fixed and free statoblasts are produced, but not in +very large numbers. The latter are broadly oval and are surrounded by a +stout chitinous ring, which often possesses irregular membranous +projections; the surface is smooth. The free statoblasts are small and +moderately elongate, the maximum breadth as a rule measuring about 2/3 +of the length; the capsule is relatively large and the ring of air-cells +is not very much broader at the ends than at the sides; the dorsal +surface of the central capsule is profusely tuberculate. The outline of +the whole structure is often somewhat irregular. + +In deference to Mr. Rousselet's opinion expressed in a letter I have +hitherto regarded the Bombay form of this species as distinct from the +African one, and there certainly is a great difference in the appearance +of specimens taken on the lower surface of stones in Igatpuri Lake and +of the types of _P. tanganyikae_, one of which is now in the collection +of the Indian Museum. The dark colour of the former, however, and their +vigorous growth appear to be directly due to environment, for these +characters disappear to a large extent in specimens growing on the stems +of water-plants in the same lake. Indeed, such specimens are exactly +intermediate between the form "_bombayensis_" and the typical form of +the species. _P. tanganyikae_ is closely allied to _P. philippinensis_, +Kraepelin, from the island of Luzon, but the latter has a smooth and +polished ectocyst devoid of annulations, and zooecia of a more elongate +and regular form. + +TYPES of the species in the British and Indian Museums, those of _P. +bombayensis_ in the latter collection. + +GEOGRAPHICAL DISTRIBUTION.--_P. tanganyikae_ is only known as yet from L. +Tanganyika in Central Africa and from Igatpuri in the Bombay Presidency. + +BIOLOGY.--In both localities the zoaria were found in shallow water. In +L. Tanganyika they were encrusting stones and shells, while at Igatpuri +they were fixed for the most part to the lower surface of stones but +were also found on the stems of water-plants. My specimens from the +Bombay Presidency were taken, on two separate occasions, at the end of +November. At that date the zoaria were already decaying and large +blanks, marked out by fixed statoblasts, were often observed on the +stones. Probably, therefore, the species flourishes during the "rains." + + +35. Plumatella punctata, _Hancock_. (Plate IV, fig. 5.) + + _Plumatella punctata_, Hancock, Ann. Nat. Hist. (2) v, p. 200, pl. iii, + fig. 1, and pl. v, figs. 6, 7 (1850). + + _Plumatella vesicularis_, Leidy, P. Ac. Philad. vii, p. 192 (1854). + + _Plumatella vitrea_, Hyatt, Comm. Essex Inst. iv, pl. ix, figs. 1, 2 + (1866). + + _Plumatella punctata_, Allman, Mon. Fresh-Water Polyzoa, p. 100, + fig. 15 (1857). + + _Plumatella vesicularis_, _id._, _ibid._ p. 101. + + _Plumatella vitrea_, Hyatt, Proc. Essex Inst. v, p. 225, + figs. 18, 19 (1868). + + _Plumatella vesicularis_, _id._, _ibid._ p. 225. + + _Hyalinella vesicularis_, Jullien, Bull. Soc. zool. France, + x, p. 133, figs. 165-172 (1885). + + _Hyalinella vitrea_, _id._, _ibid._ p. 134, figs. 173-179. + + _Plumatella punctata_, Kraepelin, Deutsch. + Suesswasserbryozoen, i, p. 126, pl. iv, figs. 115, 116; pl. + v, figs. 124, 125; pl. vii, figs. 153, 154 (1887). + + _Plumatella vesicularis_, Braem, Unters. ue. Bryozoen suessen + Wassers, p. 8, pl. i, fig. 8 (Bibl. Zool. ii) (1890). + + _Hyalinella punctata_, Loppens, Ann. Biol. lacustre, iii, p. + 163 (1908). + + _Plumatella punctata_, Annandale, Rec. Ind. Mus. v, p. 52 + (1910). + +_Zoarium._ The zoarium is entirely recumbent and often appears to form +an almost uniform flat layer instead of a dendritic body. Sometimes, +however, it is distinctly linear, with lateral branches produced +irregularly at considerable distances apart. + +_Zooecia._ The zooecia differ from those of all other species in having +a greatly swollen, soft ectocyst which can be transversely wrinkled all +over the zooecium by the action of the muscles of the polypide and is +distinctly contractile. It is mainly owing to the swollen and almost +gelatinous nature of the ectocyst that the dendritic character of the +zoarium is frequently concealed, for the method of branching is +essentially the same as that of _P. diffusa_, although the zooecia are +not so distinctly elbowed. The ectocyst is colourless or faintly tinted +with brown; as a rule it is not quite hyaline and the external surface +is minutely roughened or tuberculate. The zooecia are not emarginate or +furrowed. + +_Statoblasts._ Stationary statoblasts are not found. The free +statoblasts are variable and often asymmetrical in outline, but the free +portion of the swim-ring is always of nearly equal diameter all round +the periphery and the capsule relatively large. Some of the statoblasts +are always broad in comparison with their length. + +_Polypide._ The polypide is comparatively short and stout. European +specimens are said to have from 30 to 40 tentacles, but Indian specimens +have only from 20 to 30. + +Shrunken specimens of the less congested forms of this species closely +resemble specimens of _P. repens_, but the statoblasts are more variable +in shape and the ectocyst, even in such specimens, is thicker. Living or +well-preserved specimens cannot be mistaken for those of any other +species. Jullien regarded _P. punctata_ as the type of a distinct genus +(_Hyalinella_) but included in _Plumatella_ at least one form (P. +"_arethusa_") which probably belongs to this species. Kraepelin +distinguishes as "varieties" two phases, a summer phase ("var. +_prostrata_") and an autumn phase ("var. _densa_"). The former often +forms linear series of considerable length with only an occasional +side-branch, while in the autumn phase branching is so profuse and the +branches are so closely pressed together that the zoarium comes to +resemble a uniform gelatinous patch rather than a dendritic growth. A +phase resembling the European autumn form is the commonest in Calcutta +and I have also found one intermediate between this and Kraepelin's +"var. _prostrata_," neither having any seasonal significance in India. + +GEOGRAPHICAL DISTRIBUTION.--_P. punctata_ is widely distributed in +Europe and N. America, but in the Oriental Region it has only been found +in Calcutta and the neighbourhood. + +BIOLOGY.--In this part of India _P. punctata_ flourishes both during the +"rains" and in winter. I have found specimens in June and July and also +in December and January. The majority of them were attached to bricks, +but some were on the roots of duckweed, the stems of water-plants, and +the tips of creepers falling into water. The species is often found +together with _Stolella indica_ and also with other species of its own +genus. It is most common, in the neighbourhood of Calcutta, in that part +of the town which is near the Salt Lakes, and occurs in ponds the water +of which is slightly brackish. + + +Genus 2. STOLELLA, _Annandale_. + + _Stolella_, Annandale, Rec. Ind. Mus. iii, p. 279 (1909). + + _Stolella_, _id._, _ibid._ v, p. 53 (1910). + +TYPE, _Stolella indica_, Annandale. + +_Zoarium_. The zoarium consists of groups of zooecia (or occasionally of +single zooecia) joined together by an adherent rhizome. There is no +gelatinous investment. + +_Zooecia._ The adult zooecia resemble those of _Plumatella_ except in +being sometimes more or less upright. + +_Polypide_ and _Statoblasts._ The polypide and statoblasts resemble +those of _Plumatella_. Fixed as well as free statoblasts occur. + +This genus is closely allied to _Plumatella_, from which it is probably +derived. The root-like tube from which the zooecia arise is formed by +the great elongation of the basal part of a zooecium, and the zoaria +closely resemble those of _P. punctata_, for it is not until several +zooecia have been produced that the characteristic mode of growth +becomes apparent. + +_Stolella_ has only been found in India and is monotypic[BJ]. + + [Footnote BJ: But see p. 246 (addenda).] + + +36. Stolella indica, _Annandale_. (Plate V, figs. 3, 4.) + + _Stolella indica_, Annandale, Rec. Ind. Mus. iii, p. 279, fig. (1909). + + _Stolella indica_, _id._, _ibid._ v, p. 53 (1910). + +_Zoarium._ The zoarium is adherent and linear, having neither lateral +nor vertical branches. + +_Zooecia._ The zooecia are short and slender, erect or nearly so, +distinctly emarginate and furrowed. Their ectocyst is soft, colourless +and transparent but minutely roughened on the surface. + +_Polypide._ The tentacles number from 30 to 35 and are rather short and +stout, sometimes being slightly expanded at the tips. The stomach is +comparatively short and abruptly truncated posteriorly. + +_Statoblasts._ Both free and fixed statoblasts are found, and both are +variable in form, the latter varying in outline from the circular to the +broadly oval. The free statoblasts resemble those of _Plumatella +punctata_, but are sometimes rather more elongate. + +TYPE in the Indian Museum. + +[Illustration: Fig. 45.--Zoarium of _Stolella indica_ on stem of +water-plant (from Calcutta), x 6.] + +GEOGRAPHICAL DISTRIBUTION.--So far as we know, this species is confined +to the Indo-Gangetic Plain. Major Walton found it at Bulandshahr in the +United Provinces, and it is not uncommon in the neighbourhood of +Calcutta. + +BIOLOGY.--The zoaria of _S. indica_ are usually fixed to the roots of +duckweed or to the stems of other plants. They are often found together +with those of _P. punctata_. A slight infusion of brackish water into +the ponds in which it lives does not seem to be inimical to this +species, but I have found it in ponds in which nothing of the kind was +possible. It flourishes during the "rains" and, to judge from specimens +kept in an aquarium, is very short-lived. Major Walton found it growing +over a zoarium of _Hislopia lacustris_. + + +Subfamily B. LOPHOPINAE. + +The zoaria of this subfamily are never dendritic but form gelatinous +masses which, except in _Australella_, are cushion-shaped or sack-like. +With the possible exception of _Australella_, they possess to a limited +extent the power of moving along vertical or horizontal surfaces, but it +is by no means clear how they do so (see p. 172). The statoblasts are +remarkable for their large size, and it is noteworthy that +_Australella_, which is intermediate in structure between the +Plumatellinae and the Lophopinae, possesses statoblasts of intermediate +size. The swim-ring is always well developed, and fixed statoblasts are +unknown. + +Only two genera (_Lophopodella_ and _Pectinatella_) have been definitely +proved to occur in India, but a third (_Lophopus_[BK]) is stated to have +been found in Madras. Should it be met with it will easily be recognized +by the upright position of its polypides when their tentacles are +expanded and by the fact that the statoblasts never bear marginal +processes. + + [Footnote BK: Only two species are known, _L. crystallinus_ + (Pallas) from Europe and N. America, with oval statoblasts + that are produced and pointed at the two ends, and _L. + jheringi_, Meissner from Brazil, with irregularly polygonal + or nearly circular statoblasts.] + + +Genus 3. LOPHOPODELLA, _Rousselet_. + + _Lophopodella_, Rousselet, Journ. Quek. Micr. Club (2) ix, + p. 45 (1904). + + _Lophopodella_, Annandale, Rec. Ind. Mus. v, p. 54 (1910). + +TYPE, _Pectinatella carteri_, Hyatt. + +_Zoarium._ The zoarium consists of a circular or oval mass of no great +size. Polyparia do not form compound colonies. + +_Polypides._ The polypides lie semi-recumbent in the mass and never +stand upright in a vertical position. + +_Statoblasts._ The statoblasts are of considerable size and normally +bear at both ends a series of chitinous processes armed with double rows +of small curved spinules. + +As a rule the genus is easily recognized by means of the statoblasts, +but sometimes the processes at the ends of these structures are absent +or abortive and it is then difficult to distinguish them from those of +_Lophopus_. There is, however, no species of that genus known that has +statoblasts shaped like those of the Indian species of _Lophopodella_. + +Three species of _Lophopodella_, all of which occur in Africa, have been +described; _L. capensis_ from S. Africa, which has the ends of the +statoblast greatly produced, _L. thomasi_ from Rhodesia, in which they +are distinctly concave, and _L. carteri_ from E. Africa, India and +Japan, in which they are convex or truncate. + +The germination of the gemmule and the early stages in the development +of the polyparium of _L. capensis_ have been described by Miss Sollas +(Ann. Nat. Hist. (8) ii, p. 264, 1908). + + +37. Lophopodella carteri (_Hyatt_). (Plate III, figs. 4, 4_a_.) + + _Lophopus_ sp., Carter, Ann. Nat. Hist. (3) iii, p. 335, pl. + viii, figs. 8-15 (1859). + + ? _Lophopus_ sp., Mitchell, Q. J. Micr. Sci. London (3) ii, + p. 61 (1862). + + _Pectinatella carteri_, Hyatt, Comm. Essex Inst. iv, p. 203 + (footnote) (1866). + + _Pectinatella carteri_, Meissner, Die Moosthiere + Ost-Afrikas, p. 4 (in Mobius's Deutsch-Ost-Afrika, iv, + 1898). + + _Lophopodella carteri_, Rousselet, Journ. Quek. Micr. Club, + (2) ix, p. 47, pl. iii, figs. 6, 7 (1904). + + _Lophopus carteri_, Annandale, Rec. Ind. Mus. ii, p. 171, + fig. 3 (1908). + + _Lophopodella carteri_, _id._, _ibid._ v, p. 55 (1910). + +_Zoarium._ The zoarium as a rule has one horizontal axis longer than the +other so that it assumes an oval form when the polypides are expanded; +when they are retracted its outline is distinctly lobular. Viewed from +the side it is mound-shaped. The polypides radiate, as a rule in several +circles, from a common centre. The ectocyst is much swollen, hyaline and +colourless. + +_Polypide._ The polypide has normally about 60 tentacles, the velum at +the base of which is narrow and by no means strongly festooned. The +stomach is yellow or greenish in colour. The extended part of the +polypide measures when fully expanded rather less than 3 mm., and each +limb of the lophophore about the same. + +_Statoblast._ The statoblast is variable in shape and size but measures +on an average about 0.85 x 0.56 mm. The ends are truncate or +subtruncate; the capsule is small as compared with the swim-ring and as +a rule circular or nearly so. The processes at the two ends are variable +in number; so also are their spinules, which are arranged in two +parallel rows, one row on each side of the process, and are neither very +numerous nor set close together; as a rule they curve round through the +greater part of a circle and are absent from the basal part of the +process. + +[Illustration: Fig. 46.--Lophopodella carteri (from Igatpuri Lake). + +A=outline of a zoarium with the polypides expanded, as seen from below +through glass to which it was attached, x 4; B=outline of a zoarium with +the polypides highly contracted, as seen from above, x 4; C=statoblast, +x 75.] + + +37 _a._ Var. himalayana. + + _Lophopus lendenfeldi_, Annandale (_nec_ Ridley), J. As. + Soc. Bengal, (n. s.) iii, 1907, p. 92, pl. ii, figs. 1-4 + (1907). + + _Lophopus lendenfeldi_ var. _himalayanus_, _id._, Rec. Ind. + Mus. i, p. 147, figs. 1, 2 (1907). + + _Lophopus himalayanus_, _id._, _ibid._ ii, p. 172, fig. 4 + (1908). + +This variety differs from the typical form in having fewer tentacles and +in the fact that the marginal processes of the statoblast are abortive +or absent. + +_Pectinatella davenporti_, Oka[BL] from Japan is evidently a local race +of _L. carteri_, from the typical form of which it differs in having the +marginal processes of the statoblast more numerous and better developed. +The abortive structure of these processes in var. _himalayana_ points to +an arrest of development, for they are the last part of the statoblast +to be formed. + + [Footnote BL: Zool. Anz. xxxi, p. 716 (1907), and Annot. + Zool. Japon. vi, p. 117 (1907).] + +TYPES. The statoblasts mounted in Canada balsam by Carter and now in the +British Museum must be regarded as the types of the species named but +not seen by Hyatt. The types of the var. _himalayana_ are in the Indian +Museum and those of the subspecies _davenporti_ presumably in the +possession of Dr. Oka in Tokyo. + +GEOGRAPHICAL DISTRIBUTION.--The typical form occurs in Bombay, the W. +Himalayas and possibly Madras, and its statoblasts have been found in E. +Africa; the var. _himalayana_ has only been taken in the W. Himalayas +and the subspecies _davenporti_ in Japan. Indian localities are:--BOMBAY +PRESIDENCY, Igatpuri Lake, W. Ghats (alt. _ca._ 2,000 feet); the Island +of Bombay (_Carter_): W. HIMALAYAS, Bhim Tal, Kumaon (alt. 4,500 feet). + +BIOLOGY.--_L. carteri_ is found on the lower surface of stones and on +the stems and leaves of water-plants, usually in lakes or large ponds. +Although the zoaria do not form compound colonies by secreting a common +membrane or investment, they are markedly gregarious. The most closely +congregated and the largest zoaria I have seen were assembled amongst a +gelatinous green alga of the genus _Tolypothrix_[BM] (Myxophyceae) that +grows on the vertical stems of a plant at the edge of Igatpuri Lake; it +is noteworthy that in this case the alga seemed to take the place of the +common investment of _Pectinatella burmanica_, in which green cells are +present in large numbers (p. 237). The zoaria of _L. carteri_ are able +to change their position, and I found that if a number of them were +placed in a bottle of water they slowly came together at one spot, thus +apparently forming temporary compound colonies. Before a movement of the +whole zoarium commences its base becomes detached from its support at +the anterior end (fig. 32, p. 172), but the whole action is extremely +slow and I have not been able to discover any facts that cast light on +its exact method of production. At Igatpuri statoblasts are being +produced in considerable numbers at the end of November, but many young +zoaria can be found in which none have as yet been formed. + + [Footnote BM: Prof. W. West will shortly describe this alga, + which represents a new species, in the Journ. Asiat. Soc. + Bengal, under the name _Tolypothrix + lophopodellophila_.--_April 1911_.] + +The larva of a fly of the genus _Chironomus_ is often found inhabiting a +tube below zoaria of _L. carteri_. It is thus protected from its enemies +but can protrude its head from beneath the zoarium and seize the small +animals on which it preys. + + +Genus 4. PECTINATELLA, _Leidy_. + + _Cristatella_, Leidy, P. Ac. Philad. v, p. 265 (1852). + + _Pectinatella_, _id._, _ibid._, p. 320. + + _Pectinatella_, Allman, Mon. Fresh-Water Polyzoa, p. 81 + (1857). + + _Pectinatella_, Hyatt, Proc. Essex Inst. v, p. 227, fig. 20 + (1867). + + _Pectinatella_, Kraepelin, Deutsch. Suesswasserbryozoen, i, + p. 133 (1887). + + _Pectinatella_, Oka, Journ. Coll. Sci. Tokyo, iv, p. 89 + (1891). + +TYPE, _Pectinatella magnifica_, Leidy. + +This genus is closely allied to _Lophopodella_, from which it is often +difficult to distinguish young specimens. Adult zoaria are, however, +always embedded together in groups in a gelatinous investment which they +are thought to secrete in common[BN], and the statoblasts are entirely +surrounded by processes that bear curved spinules at their tips only. +The polypides have the same semi-recumbent position as those of +_Lophopodella_ but are larger than those of any species of +_Lophopodella_ or _Lophopus_ yet known. The statoblasts are larger than +those of any other Plumatellidae. + + [Footnote BN: It is now perhaps open to doubt whether the + investment is actually secreted by the polyzoon, for Prof. + W. West has discovered in it the cells of an alga belonging + to a genus which habitually secretes a gelatinous investment + of its own (see p. 238, _post._).--_April 1911._] + +The type-species was originally found in N. America but has since been +taken in several localities in continental Europe. Except this and the +Indian form only one species is known, namely _P. gelatinosa_ from +Japan. _P. magnifica_ has circular statoblasts with long marginal +processes, while in _P. gelatinosa_ the statoblasts are subquadrate and +in _P. burmanica_ almost circular, both Asiatic forms having very short +marginal processes. + +The compound colonies formed by _Pectinatella_ are often of great size. +Those of _P. gelatinosa_ are sometimes over 2 metres in length, while +those of _P. burmanica_ in the Sur Lake appeared to be only limited as +regards their growth by the shallowness of the water in which the reeds +to which they were attached were growing. Some were observed that were +over 2 feet long. + + +38. Pectinatella burmanica, _Annandale_. (Plate III, fig. 5.) + + _Pectinatella burmanica_, Annandale, Rec. Ind. Mus. ii, + p. 174, fig. 5 (1908). + + _Pectinatella burmanica_, _id._, _ibid._ v, p. 56 (1910). + + _Pectinatella burmanica_, _id._, Spol. Zeyl. vii, p. 63, + pl. i, fig. 3 (1910). + +_Zoarium._ The zoaria are circular or nearly so except when about to +undergo division, in which case they are constricted in the middle. As a +rule they measure nearly an inch (2 cm.) in diameter. The polypides have +a definite arrangement in each zoarium, being divided into four groups, +each of which has a fan-like form. In the first place they are separated +into two main divisions in a line running through the centre of the +zoarium, and secondly each main division is separated into two +subordinate ones in a line running across the other at right angles. The +number of zoaria joined together in a single compound colony is very +variable; sometimes there are only about half a dozen and sometimes +several hundreds. The common investment in living colonies is often as +much as two inches thick and has a translucent dark greenish colour due +to the presence in it of green cells. + +[Illustration: Fig. 47.--_Pectinatella burmanica._ + +A=polypide with the lophophore expanded, x 15; _a_=oesophagus; +_b_=cardiac limb of stomach; _c_=stomach; _d_=rectum; _e_=anus; +_f_=funiculus. [The muscles are omitted and the external tubercles are +only shown on part of the polypide. The specimen is from the Sur Lake, +Orissa.] B=statoblast from Ceylon, x 35.] + +_Polypide._ The polypide can be extruded for a distance of at least 5 +mm. Its whole external surface is covered with minute tubercles. There +are about 90 tentacles, which are long and slender, the velum at their +base being narrow and almost straight. The stomach is of considerable +stoutness. + +_Statoblast._ The statoblasts are of large size, measuring from 1 to +1.75 mm. in diameter. In form they are almost circular, but one side is +always slightly flattened. The marginal processes are very short and +bear a single pair of hooks at the tip. The capsule is circular and +small as compared with the free part of the swim-ring. + +TYPE in the Indian Museum. + +_P. burmanica_ is evidently a near relation of _P. gelatinosa_, Oka, +from Japan, differing from that species in the shape of the statoblasts +and in having much longer tentacles. The arrangement of the polypides in +the zoarium and the general structure of the statoblasts are very +similar in the two species. + +GEOGRAPHICAL DISTRIBUTION.--_P. burmanica_ was originally described from +a swamp at Kawkareik in the Amherst district of Tenasserim but has also +been found in the Sur Lake near Puri in Orissa. Dr. A. Willey obtained +specimens from a pool by the roadside between Maradankadewela and +Galapitagala, at the foot of Ritigala, N. Central Province, Ceylon. + +BIOLOGY.--The first specimen obtained was a statoblast fixed to a tube +of the oligochaete worm _Aulophorus tonkinensis_ taken at Kawkareik in +March. At the same time young zoaria, which did not yet possess a common +investment, were found on a leaf growing on a twig which drooped into +the water. Large compound colonies were taken in Orissa in October. They +completely encased the stems of reeds, thus forming hollow cylinders, +but slipped from their supports when the reeds were pulled out of the +water. In life they resembled gelatinous algae rather than animals and +exhibited a striking similarity to masses of zoaria of _Lophopodella +carteri_ surrounded by such algae. Some of the colonies were evidently +dying and contained few polypides in a living condition, but many +statoblasts; others were in a flourishing condition and were producing +larvae and statoblasts simultaneously. + +A piece of a colony full of larvae was placed before midday in an +aquarium, which was kept in a shady verandah. Large numbers of larvae +were set free almost immediately. They measured about 2 mm. in length +and were distinctly pear-shaped; each contained a pair of polypides, +which occupied a comparatively small part of the interior, the whole of +the broader half being hollow. The larvae swam slowly, broad-end-first, +by means of the cilia with which their surface was covered, occasionally +gyrating on their long axis and always adopting an erratic course. +Towards evening they showed signs of settling down, frequently touching +the glass of the aquarium with their broad ends and sometimes remaining +still in this position for some minutes. Many attempts were, however, +made before fixation was completed, and this did not occur until after +nightfall. By next morning every larva was fixed to the glass and had +everted its two polypides. Unfortunately I was not able to trace the +development further, but young compound colonies were found in which the +secretion of the common investment had just commenced. The zoaria in +these colonies measured about 1 cm. in diameter and already contained +many polypides each. + +Oka has described the development from the statoblast of the allied +Japanese species. He found that each statoblast produced in the first +instance a single polypide, and that the statoblasts, which were +produced in autumn, lay dormant through the winter and germinated in +spring. As the Sur Lake begins to undergo desiccation as soon as the +"rains" cease, the statoblasts in it probably do not germinate until the +break of the next "rains" about the middle of June. I have had dried +statoblasts in my possession for over two years. Their cellular contents +appear to be in good condition, although the cells show no signs of +development; but they have not germinated in my aquarium, in which some +of them have now been kept for more than six months. + +The green cells of the common investment are peculiar bodies that +deserve further study than it has yet been possible to devote to them. +Each cell is of ovoid form, varying somewhat in size but as a rule +measuring about 0.03 x 0.008 mm. There can be no doubt that these bodies +represent a stage in the life-history of an alga[BO]. Diatoms, bacilli +and other minute plants are often present in the membrane as well as the +characteristic green cells, but do not form a constant feature of it. + + [Footnote BO: Professor W. West identifies this algae as + _Dactylococcopsis pectinatellophila_, new species. It will + be described, before the publication of this book, in the + Journ. As. Soc. Bengal (1911). Prof. West has found, + associated more or less fortuitously with _P. burmanica_, + another alga, namely _Microcystis orissica_, also a new + species.--_April 1911._] + + + + +APPENDIX TO THE VOLUME. + + +HINTS ON THE PREPARATION OF SPECIMENS. + +_To preserve Spongillidae._--Spongillidae must be preserved dry or in very +strong alcohol. Formalin should not be used. + +_To clean siliceous sponge spicules._--Place small fragments of the +dried sponge (if alcohol is present, the reaction is apt to be violent) +in a test tube, cover them with strong nitric acid and boil over the +flame of a Bunsen burner or small spirit lamp until the solid particles +disappear. Add a large quantity of water to the acid and filter through +pure cellulose filter-paper, agitating the liquid repeatedly. Pass clean +water in considerable quantities through the filter-paper and dry the +latter carefully; place it in a spirally coiled wire and ignite with a +match, holding the wire in such a way that the spicules released by the +burning of the paper fall into a suitable receptacle. They may then be +picked up with a camel's-hair brush and mounted in Canada balsam. + +_To examine the skeleton of a Spongillid._--Cut thin hand-sections with +a sharp scalpel, dehydrate if necessary, and mount in Canada balsam. + +_To prepare gemmules for examination._--Place the gemmules dry in a +watch-glass with a few drops of strong nitric acid. When gas is given +off freely add water in considerable quantities. Remove the gemmules +with a camel's-hair brush to clean water, then to 50%, 70%, 90% and +absolute alcohol in succession, leaving them for an hour in each +strength of spirit. Clear with oil of cloves and mount in Canada balsam. + +_To ascertain the presence of bubble-cells in the parenchyma of a +Spongillid._--Tease up a small piece of the sponge with a pair of +needles, mount under a thin cover-slip in strong spirit, and examine +under a high power of the microscope. + +_To preserve Hydra in an expanded condition._--Place the polyp in a +watch-glass of clean water and wait until its tentacles are expanded. +Heat a few drops of commercial formaldehyde and squirt the liquid while +still hot at the _Hydra_, which will be killed instantaneously. Remove +it to a solution of formaldehyde and spirit of the following formula:-- + + Commercial formaldehyde 1 part. + Absolute alcohol 3 parts. + Distilled water 7 parts. + +Then pass the _Hydra_ through 50% and 70% alcohol and keep in 90%. + +_To examine the capsules of the nettle-cells._--Place a living _Hydra_ +in a small drop of water on a slide and press a thin cover-slip down +upon it. + +_To preserve freshwater polyzoa in an expanded condition._--Place the +polyzoa in a glass tube full of clean water and allow them to expand +their tentacles. Drop on them gradually when they are fully expanded a +2% aqueous solution of cocaine, two or three drops at a time, until +movement ceases in the tentacles. Then pour commercial formaldehyde into +the tube in considerable quantities. Allow the whole to stand for half +an hour. If it is proposed to stain the specimens for anatomical +investigation, they should then be removed through 50% and 70% to 90% +alcohol. If, on the other hand, it is desired to keep them in a +life-like condition they may be kept permanently in a solution of one +part of commercial formaldehyde in four parts of water. Care must be +taken that the process of paralyzing the polypides is not unduly +prolonged, and it is always as well to preserve duplicate specimens in +spirit or formalin with the lophophore retracted. + +_To prepare statoblasts for examination._--Place the statoblasts for a +few minutes in strong nitric acid. Then remove the acid with water, pass +through alcohol, clear with oil of cloves, and mount in a small quantity +of Canada balsam under a cover-slip, taking care that the statoblasts +lie parallel to the latter. + + + + +ADDENDA. + + +The following addenda are due mainly to an expedition to the lakes of +Kumaon in the W. Himalayas undertaken by Mr. S. W. Kemp in May, 1911. + + +PART I. + + +Genus SPONGILLA. + + +Subgenus EUSPONGILLA (p. 69). + +1 a. Spongilla lacustris, subsp. reticulata (p. 71). + +Specimens were taken in the lake Malwa Tal (alt. 3600 feet) in Kumaon, +while others have recently been obtained from the Kalichedu +irrigation-tank in the Pagnor _talug_ of the Nellore district, Madras +(_G. H. Tipper_). + +4. Spongilla cinerea (p. 79). + +Specimens were taken in Naukuchia Tal (alt. 4200 feet) in Kumaon. They +have a pale yellow colour when dry. This sponge has not hitherto been +found outside the Bombay Presidency. + + +Subgenus EUNAPIUS (p. 86). + +8. Spongilla carteri (p. 87). + +Specimens were taken in Bhim Tal (alt. 4450 feet) and Sat Tal (alt. 4500 +feet). Some of them approach the variety _cava_ in structure. + + +Subgenus STRATOSPONGILLA (p. 100). + +12. Spongilla bombayensis (p. 102). + +Add a new variety:-- + +13 a. Var. pneumatica, nov. + + (i.) The sponge forms a flat layer of a pale brownish colour + as a rule with short and very delicate vertical branches. + In one specimen it takes the form of an elegant cup + attached, only at the base, to a slender twig. + + (ii.) The gemmules are covered, outside the spicules, by a + thick pneumatic coat of irregular formation and with + comparatively large air-spaces. + + (iii.) The gemmule-spicules are regularly sausage-shaped. + +TYPES in the Indian Museum. + +HABITAT. Naukuchia Tal (alt. 4200 feet), Kumaon, W. Himalayas (_S. W. +Kemp_). + + +Genus EPHYDATIA (p. 108). + +After _Ephydatia meyeni_, p. 108, add:-- + + +Ephydatia fluviatilis, _auct._ + + ? _Ephydatia fluviatilis_, Lamouroux, Encyclop. Method. ii, + p. 327 (1824). + + _Spongilla fluviatilis_, Bowerbank (_partim_), Proc. Zool. + Soc. London, 1863, p. 445, pl. xxxviii, fig. 1. + + _Ephydatia fluviatilis_, J. E. Gray (_partim_), Proc. Zool. + Soc. London, 1867, p. 550. + + _Meyenia fluviatilis_, Carter (_partim_), Ann. Nat. Hist. + (5) vii, p. 92, pl. vi, fig. 11 _a_, _b_ (1881). + + _Ephydatia fluviatilis_, Vejdovsky, Abh. k. Boehm. + Gesellschaft Wiss. xii, p. 24, pl. i, figs. 1, 2, 7, 10, 14, + 19 (1883). + + _Ephydatia fluviatilis_, _id._, P. Ac. Philad. 1887, p. 178. + + _Meyenia fluviatilis_ var. _gracilis_, Potts, _ibid._, p. + 224. + + _Meyenia robusta_, _id._, _ibid._, p. 225, pl. ix, fig. 5. + + _Ephydatia fluviatilis_, Weltner, Arch. Naturg. Berlin, 1895 + (i) p. 122. + + _Ephydatia robusta_, Annandale, Journ. As. Soc. Bengal, + 1907, p. 24, fig. 7. + + _Ephydatia fluviatilis_, Weltner, in Brauer's + Suesswasserfauna Deutschlands xix, Suesswasserschwaemme, p. + 185, figs. 316, 317 (1909). + + _Ephydatia fluviatilis_, Annandale, P. U. S. Mus. xxxviii, + p. 649 (1910). + +[Many more references to this common species might be cited, but those +given above will be sufficient.] + +This species only differs from _E. meyeni_ in the following +characters:-- + + (i.) there are no bubble-cells in the parenchyma; + + (ii.) there is less spongin in the skeleton, which is less compact; + + (iii.) the gemmule-spicules are longer, the shafts being as a rule + longer than the diameter of the rotulae; + + (iv.) the gemmules are armed with a single row of regularly + arranged spicules embedded in pneumatic tissue with + minute air-spaces. + +The sponge is a variable one and several "varieties" have been described +from different parts of the world. My Indian specimens come nearest to +the form described by Potts as _Meyenia robusta_, but have rather more +slender skeleton-spicules and more elongate gemmule-spicules. The latter +also appear to be less frequently "monstrous." + +TYPE ? + +GEOGRAPHICAL DISTRIBUTION.--_E. fluviatilis_ is widely distributed in +Europe and occurs in N. America,[BP] S. Africa (var. _capensis_, +Kirkpatrick), Australia, and Japan. Specimens were obtained by Mr. Kemp +from several lakes in Kumaon, namely Naukuchia Tal (alt. 4200 feet), +Bhim Tal (4450 feet), Sat Tal (4500 feet), and Naini Tal (6300 feet). +The gemmules from Bhim Tal referred by me to _E. robusta_ (Potts) also +belong to this species. + + [Footnote BP: Most of the forms assigned by Potts to this + species belong to the closely allied _E. muelleri_ + (Lieberkuehn).] + +_Biology._ The external form of the sponge is due in great part to its +environment. Specimens on small stones from the bottom of the Kumaon +Lakes consist of thin disk-like films, often not more than a few +centimetres in diameter and a few millimetres thick: others, growing on +thin twigs, are elevated and compressed, resembling a cockscomb in +appearance, while others again form nodules and masses of irregular form +among the branches of delicate water-weeds. Some of these last are +penetrated by zoaria of _Fredericella indica_. + +Weltner has published some very interesting observations on the seasonal +variation of minute structure in European representatives of the species +(Arch. Naturg. Berlin, lxxiii (i), p. 273 1907) and has discussed the +formation of the abnormal spicules that sometimes occur (_ibid._ lxvii +(Special Number), p. 191, pls. vi, vii, figs. 27-59, 1901). + + +Genus CORVOSPONGILLA (p. 122). + +After _Corvospongilla burmanica_, p. 123, add a new species:-- + + +Corvospongilla caunteri, nov. + +_Sponge_ forming thin films of considerable area not more than 3 or 4 +mm. thick, of a bright green colour, moderately hard but friable. The +surface smooth; oscula inconspicuous, surrounded by shallow and +ill-defined radiating furrows; a very stout basal membrane present. + +[Illustration: Fig. 48.--_Corvospongilla caunteri_ (type, from Lucknow). + +A=Gemmule; B=gemmule-spicules; C=flesh-spicules; D=Skeleton-spicules.] + +_Skeleton_ reticulate but almost devoid of spongin, the reticulations +close but formed mainly by single spicules; skeleton-fibres barely +distinguishable. A close layer of spicules lying parallel to the basal +membrane. + +_Spicules._ Skeleton-spicules variable in size and shape, almost +straight, as a rule smooth, moderately stout, blunt or abruptly pointed; +sometimes roughened or spiny at the tips, often sharply pointed. +Flesh-spicules minute, few in number, with smooth, slender shafts which +are variable in length, never very strongly curved; the terminal spines +relatively short, not strongly recurved. Gemmule-spicules +amphistrongylous or amphioxous, irregularly spiny, slender, of variable +length. + +_Gemmules_ free in the substance of the sponge, spherical or somewhat +depressed, very variable in size but never large, having a thick +external pneumatic coat in which the air-spaces are extremely small and, +inside this coat, a single rather sparse layer of spicules lying +parallel to the gemmule. A single depressed aperture present. + +TYPE in the Indian Museum. + +HABITAT. Hazratganj, Lucknow; on piers of bridge in running water (_J. +Caunter_, 29-30. iv. 11). + +The structure of the gemmules of this species differs considerably from +that in any other known species of the genus, in which these structures +are usually adherent and devoid of a true pneumatic coat. In some of the +gemmules before me this coat measures in thickness about 1/9 of the +total diameter of the gemmule. _C. caunteri_ is the first species of +_Corvospongilla_ to be found in the Indo-Gangetic plain. + + +PART II. + + +Genus HYDRA (p. 147). + + +25. Hydra oligactis (p. 158). + +Mr. Kemp found this species common in Bhim Tal in May. His specimens, +which were of a reddish-brown colour in life, appear to have been of +more vigorous constitution than those taken by Major Stephenson in +Lahore. Some of them had four buds but none were sexually mature. + + +PART III. + + +Genus FREDERICELLA (p. 208). + + +28. Fredericella indica (p. 210). + +This species is common in some of the Kumaon lakes, in which it grows, +at any rate at the beginning of summer, much more luxuriantly than it +does in the lakes of the Malabar Zone in autumn, forming dense bushy +masses on the under surface of stones, on sticks, &c. The vertical +branches often consist of many zooecia. Mr. Kemp took specimens in Malwa +Tal, Sath Tal, and Naini Tal (alt. 3600-6300 feet). + + +Genus PLUMATELLA (p. 212). + + +30. Plumatella emarginata (p. 220). + +Mr. Kemp took bushy masses of this species in Malwa Tal and Bhim Tal. + + +32. Plumatella diffusa (p. 223). + +This species is common in Malwa Tal and Bhim Tal in May. + + +33. Plumatella allmani (p. 224). + +Mr. Kemp only found this species in Malwa Tal, in which (at any rate in +May) it appears to be less abundant than it is in Bhim Tal in autumn. +Mr. Kemp's specimens belong to the form called _P. elegans_ by Allman. + + +34. Plumatella tanganyikae (p. 225). + +Specimens taken by Mr. Kemp, somewhat sparingly, in Bhim Tal and Sath +Tal in May exhibit a somewhat greater tendency towards uprightness of +the zooecia than those I found in autumn in Igatpuri lake. The ectocyst +is, in the former specimens, of a deep but bright reddish-brown. The +zoaria are attached to twigs and small stones. + + +Genus STOLELLA (p. 229). + +After Stolella indica, p. 229, add a new species:-- + + +Stolella himalayana, nov. + +This species may be distinguished from _S. indica_ by (i) its entirely +recumbent zooecia, and (ii) the lateral branches of its zoarium. + +[Illustration: Fig. 49.--_Stolella himalayana_ (types, from the Kumaon +lakes). + +A. The greater part of a young zoarium. B. Part of a much older +zoarium.] + +_Zoarium_ entirely recumbent, consisting of zooecia joined together, +often in groups of three, by slender, transparent, tubular processes. +These processes are often of great relative length; they are formed by a +modification of the posterior or proximal part of the zooecia, from +which they are not separated by a partition, and they increase in length +up to a certain point more rapidly than the zooecia proper. A zooecium +often gives rise first to an anterior daughter-zooecium, the proximal +part of which becomes elongate and attenuated in due course, and then to +a pair of lateral daughter-zooecia situated one on either side. As a +result of this method of budding a zoarium with a close superficial +resemblance to that of _Paludicella_ is at first produced, but as the +colony increases in age and complexity this resemblance largely +disappears, for the zooecia and their basal tubules grow over one +another and often become strangely contorted (fig. 49). + +_Zooecia_ elongate and slender, flattened on the ventral, strongly +convex on the dorsal surface; rather deep in proportion to their +breadth; the ectocyst colourless, not very transparent except on the +stolon-like tubular part; dorsal keel and furrow as a rule absent; +orifice unusually inconspicuous, situated on a tubercle on the dorsal +surface. + +_Polypide_ stout and short; the tip of the fundus of the stomach capable +of very complete constriction; the retractor muscles unusually short and +stout. + +_Statoblasts._ Only free statoblasts have been observed. They resemble +those of _S. indica_, but are perhaps a little longer and more elongate. + +TYPES in the Indian Museum. + +The discovery of this species makes it necessary to modify the diagnosis +of the genus, the essential character of which, as distinguishing it +from _Plumatella_, is the differentiation of the proximal part of some +or all of the zooecia to form stolon-like tubules. From _Stephanella_, +Oka, it is distinguished by the absence of a gelatinous covering, and by +the fact that all the zooecia are attached, at least at the base, to +some extraneous object. + +HABITAT. Malwa Tal, Kumaon (alt. 3600 feet), W. Himalayas (_Kemp_, May +1911). + +BIOLOGY. Mr. Kemp took three specimens, all attached to the lower +surface of stones. They contained few statoblasts and were evidently in +a condition of vigorous growth. Between the lateral branches new +polyparia were developing in several instances from free statoblasts, +each of which appeared to contain two polypides. + + + + +ALPHABETICAL INDEX. + + +All names printed in italics are synonyms. + +When more than one reference is given, the page on which the description +occurs is indicated by thickened numerals. + + alba (Euspongilla) (Spongilla), 8, 9. + alba (Spongilla), 4, 22, 63, ~76~. + alba _var._ bengalensis (Spongilla), 4, 22, 63, ~77~. + alba _var_. cerebellata (Spongilla), 22, 63, ~76~. + _alba_ var. _marina_ (_Spongilla_), ~77~. + _Alcyonella_, 212. + Alcyonellea, 185. + allmani (Plumatella), 7, 8, 9, 23, 188, ~224~, 246. + _allmani_ var. _diffusa_ (_Plumatella_), 223. + _allmani_ var. _dumortieri_ (_Plumatella_), 222. + _attenuata_ (_Hydra_), 148, 158. + _aurantiaca_ (_Hydra_), 148. + aurea (Pectispongilla), 9, 22, 63, ~106~. + aurea _var._ subspinosa (Pectispongilla), 63, ~107~. + + _benedeni_ (_Alcyonella_), 220. + bengalensis (Bowerbankia), 189. + bengalensis (Membranipora), 23. + bengalensis (Spongilla), 77. + bengalensis (Victorella), 4, 8, 9, 23, 187, ~195~. + blembingia (Ephydatia), 54. + bogorensis (Ephydatia), 54. + _bombayensis_ (_Plumatella_), 225. + bombayensis (Spongilla), 22, 63, 100, ~102~, 241. + bombayensis (Stratospongilla) (Spongilla), 8, 9. + Bowerbankia, 187, ~189~. + _brunnea_ (_Hydra_), 148. + burmanica (Corvospongilla), 8, 22, 64, ~122~. + burmanica (Pectinatella), 8, 10, 23, 188, ~235~. + + calcuttana (Spongilla), 96. + _cambodgiensis_ (_Norodonia_), 202. + _Carterella_, 108. + carteri (Eunapius) (Spongilla), 7, 8, 9, 10. + _carteri_ (_Eunapius_), 87. + carteri (Lophopodella), 7, 8, 23, 188, ~232~, 233. + _carteri_ (_Lophopus_), 232. + _carteri_ (_Pectinatella_), 231, + carteri (Spongilla), 4, 22, 63, 86, ~87~, 241. + carteri _var._ cava (Spongilla), 22, 63. + carteri _var._ himalayana (Lophopodella), 23, 188. + carteri _var._ lobosa (Spongilla), 22, 63. + carteri _var._ mollis (Spongilla), 22, 63. + caudata (Bowerbankia), 189. + caudata _subsp._ bengalensis (Bowerbankia), 23, 189. + caunteri (Corvospongilla), 243. + cava (Spongilla), 88. + cerebellata (Spongilla), 76. + ceylonensis (Irene), 22, 140. + Cheilostomata, 184. + Chlorella, 50. + cinerea (Euspongilla) (Spongilla), 9. + cinerea (Spongilla), 22, 63, 72, 79, 241. + clementis (Stratospongilla) (Spongilla), 53. + coggini (Stratospongilla) (Spongilla), 53. + colonialis (Loxosomatoides), 23. + _contecta_ (_Spongilla_), 95. + _coralloides_ (_Plumatella_), 217. + Corvospongilla, 64, ~122~, 243. + crassior (Spongilla), 98. + crassissima (Eunapius) (Spongilla), 9. + crassissima (Spongilla), 4, 22, 63, ~98~. + crassissima _var._ crassior (Spongilla), 23, 63. + _crateriformis_ (_Meyenia_), 83. + _crateriformis_ (_Ephydatia_), 83, 84. + crateriformis (Euspongilla) (Spongilla), 8, 9. + _crateriformis_ (_Meyenia_), 83. + crateriformis (Spongilla), 22, 63, ~83~. + _Cristatella_, 235. + Cristatellina, 206. + Ctenostomata, 184, 185, 187, ~189~. + Cyclostomata, 184. + + decipiens (Spongilla), 54, 96, ~97~. + diffusa (Plumatella), 7, 8, 9, 23, 188, ~223~, 245. + _di[oe]cia_ (_Hydra_), 158. + Dosilia, 64, ~110~. + + _Echinella_, 199. + _elegans_ (_Plumatella_), 224. + Eleutheroblastea, 146, 147. + emarginata (Plumatella), 4, 8, 9, 10, 23, 188, 218, ~220~, 245. + _emarginata_ var. _javanica_ (_Plumatella_), 221. + Entoprocta, 183. + Ephydatia, 64, ~108~, 242. + _erinaceus_ (_Spongilla_), 114. + Eunapius, 63, ~86~, 241. + Euspongilla, 63, 67, ~69~, 241. + + filamentata (Syncoryne), 22, 140. + fluviatilis (Ephydatia), 109, ~242~. + _fluviatilis_ (_Meyenia_), 242. + fluviatilis (Spongilla), 108, 242. + _fluviatilis_ var. _gracilis_ (_Meyenia_), 242. + fortis (Ephydatia), 52, 53. + fragilis (Spongilla), ~95~, 96. + fragilis _subsp._ calcuttana (Eunapius) (Spongilla), 9. + fragilis _subsp._ calcuttana (Spongilla), 22, 63. + fragilis _subsp._ decipiens (Spongilla), 22, 63. + Fredericella, 188, ~208~, 245. + FREDERICELLIDAE, 188, ~208~. + _friabilis_ (_Spongilla_), 87. + fruticosa (Plumatella), 4, 7, 8, 9, 23, 188, ~217~, 218. + _fusca_ (_Hydra_), 158, 159. + + Gecarcinucus, 10. + gemina (Eunapius) (Spongilla), ~8~. + gemina (Spongilla), 22, 63, ~97~. + _glomerata_ (_Spongilla_), 95. + _grisea_ (_Hydra_), 148, 149. + Gymnolaemata, 184, 187. + + Halichondrina, 65. + hemephydatia (Euspongilla) (Spongilla), 8. + hemephydatia (Spongilla), 22, 63, ~82~. + _hexactinella_ (_Hydra_), 148. + himalayana (Lophopodella), 233. + himalayana (Stolella), 246. + _himalayanus_ (_Lophopus_), 233. + Hislopia, 187, ~199~. + Hislopidees, 199. + HISLOPIIDAE, 187, ~199~. + Homodiaetidae, 191. + _Hyalinella_, 212. + Hydra, 146, ~147~, 245. + Hydraidae, 147. + HYDRIDAE, 146, 147. + hydriforme (Polypodium), 142. + Hydrozoa, 146. + + _indica_ (_Ephydatia_), 83. + indica (Fredericella), 9, 23, 188, ~209~, 245. + indica (Spongilla), 22, 63, ~100~. + indica (Stolella), 4, 9, 23, 188, ~229~. + indica (Stratospongilla), (Spongilla), 9. + + javanica (Plumatella), 4, 8, 9, 23, 188, ~221~, 222. + + kawaii (Limnocodium), 141. + + lacroixii (Membranipora), 23. + lacustris (Cordylophora), 141. + _lacustris_ (_Euspongilla_), 69. + lacustris (Hislopia), 4, 8, 9, 23, 187, 199, ~202~, 204. + lacustris (Spongilla), 63, 67, ~69~. + lacustris _subsp._ moniliformis (Hislopia), 9, 23, 187. + lacustris _subsp._ reticulata (Spongilla), 4, 8, 9, 22, 63, ~71~, 241. + _lacustris_ var. _bengalensis_ (_Spongilla_), 77. + lapidosa (Corvospongilla), 9, 22, 64, ~124~. + _lapidosa_ (_Spongilla_), 124. + latouchiana (Trochospongilla), 4, 8, 9, 22, 64, ~115~. + _leidyi_ (_Trochospongilla_), 115. + _lendenfeldi_ (_Lophopus_), 233. + _lendenfeldi_ var. _himalayanus_ (_Lophopus_), 233. + lobosa (Spongilla), 89. + LOPHOPINAE, 188, 211, ~231~. + Lophopodella, 8, 188, ~231~. + _Lophopus_, 8, 232. + _lordii_ (_Spongilla_), 95. + loricata (Spongilla), ~122~. + _loricata_ var. _burmanica_, (_Spongilla_), 122. + _lucifuga_ (_Plumatella_), 217, 220, 224. + + magnifica (Pectinatella), 235. + meyeni (Ephydatia), 7, 9, 17, 22, 64, ~108~. + _meyeni_ (_Spongilla_), 108. + _Meyenia_, 108, 113. + microsclerifera (Euspongilla) (Spongilla), 53. + mollis (Spongilla), 88. + moniliformis (Hislopia), 204. + _mon[oe]cia_ (_Hydra_), 158. + _morgiana_ (_Spongilla_), 95. + _muelleri_ (_Ephydatia_), 109, 243. + _muelleri_ subsp. _meyeni_ (_Ephydatia_), 109. + + _Norodonia_, 199. + + oligactis (Hydra), 7, 22, 146, ~158~, 159, 245. + _orientalis_ (_Hydra_), 148, 149. + _ottavaensis_ (_Spongilla_), 95. + + _pallens_ (_Hydra_), 148. + Paludicella, 187, ~192~. + PALUDICELLIDAE, 187, ~191~. + Paludicellidees, 191. + Paludicellides, 191. + Paludicellina, 186, 187, ~190~. + paulula (Spongilla), 120. + _pavida_ (_Victorella_), 194, 195. + Pectinatella, 188, ~235~. + pectinatellophila (Dactyloccopsis), 238. + Pectispongilla, 63, ~106~. + pennsylvanica (Trochospongilla), 9, 22, 64, ~118~. + _pennsylvanica_ (_Tubella_), 118. + _pentactinella_ (_Hydra_), 149. + philippinensis (Euspongilla) (Spongilla), 53. + phillottiana (Trochospongilla), 4, 8, 9, 22, 64, ~117~. + Phylactolaemata, 185, 188, ~206~. + Plumatella, 188, 208, ~212~, 245. + PLUMATELLIDAE, 188, ~211~. + Plumatellina, 188, ~206~. + PLUMATELLINAE, 188, 211, ~212~. + plumosa (Dosilia), 8, 9, 22, 64, ~111~. + _plumosa_ (_Ephydatia_), 111. + _plumosa_ (_Meyenia_), 111. + _plumosa_ (_Spongilla_), 111. + pneumatica (Stratospongilla) (Spongilla), 241. + _polypus_ (_Hydra_), 148, 159. + Polyzoa, 183. + _princeps_ (_Plumatella_), 220. + _princeps_ var. _emarginata_ (_Plumatella_), 220. + _princeps_ var. _fruticosa_ (_Plumatella_), 217. + proliferens (Euspongilla) (Spongilla), 8, 9, 10. + proliferens (Spongilla), 4, 8, 22, 63, ~72~. + Proterospongia, 27. + _punctata_ (_Hyalinella_), 228. + punctata (Plumatella), 9, 188, ~227~. + + _repens_ (_Plumatella_), 217, 223. + reticulata (Spongilla), 71. + _rhaetica_ (_Hydra_), 158. + _robusta_ (_Ephydatia_), 109, 242. + _robusta_ (_Meyenia_), 242. + _roeselii_ (_Hydra_), 158. + ryderi (Microhydra), 141. + + schilleriana (Sagartia), 2, 22, 140. + schilleriana _subsp_. exul (Sagartia), 22. + _sibirica_ (_Spongilla_), 95. + _sinensis_ (_Norodonia_), 202. + sinensis (Stratospongilla) (Spongilla), 53. + _socialis_ (_Hydra_), 158. + sowerbii (Limnocodium), 141. + Spongilla, 63, ~67~, 86, 241. + Spongilladae, 65. + SPONGILLIDAE, 65. + Stolella, 188, ~229~, 246. + Stolonifera, 185. + Stratospongilla, 63, ~100~, 241. + _stricta_ (_Plumatella_), 217. + subspinosa (Pectispongilla), 107. + sumatrana (Stratospongilla) (Spongilla), 53. + + tanganyikae (Limnocnida), 142. + tanganyikae (Plumatella), 9, 23, 188, ~225~, 246. + Trachospongilla, 64, ~113~. + _Trachyspongilla_, 108. + travancorica (Euspongilla) (Spongilla), 9. + travancorica (Spongilla), 22, 63, ~81~. + _trembleyi_ (_Hydra_), 148. + Tubella, 64, 113, ~120~. + + ultima (Spongilla), 22, 63, ~105~. + ultima (Stratospongilla) (Spongilla), 9. + + VESICULARIDAE, 189. + Vesicularina, 186, 187, ~189~. + _vesicularis_ (_Hyalinella_), 228. + _vesicularis_ (_Plumatella_), 227, 228. + vesparioides (Tubella), 8, 22, 64, ~120~. + vesparium (Tubella), 54. + vestita (Bimeria), 22, 139. + Victorella, 189, ~194~. + Victorellidae, 191. + Victorellides, 191. + viridis (Hydra), 147. + _vitrea_ (_Hyalinella_), 228. + _vitrea_ (_Plumatella_), 227, 228. + vulgaris (Hydra), 4, 8, 9, 10, 22, 130, 146, ~148~, 149, 158. + + whiteleggei (Cordylophora), 141. + + yunnanensis (Euspongilla) (Spongilla), 53. + + + + + PLATE I. + + SPECIMENS OF _Spongilla_ PRESERVED IN SPIRIT. + + + Figs. 1-3. _S. (Euspongilla) alba_ var. _bengalensis_ (nat. + size) from ponds of brackish water at Port Canning in the + delta of the Ganges. Fig. 1 represents the type-specimen of + the variety, and was taken in the winter of 1905-6. Figs. 2 + and 3 represent specimens taken in the same ponds in the + winters of 1907 and 1908 respectively. + + Fig. 4. _Spongilla_ sp. (? abnormal form of _S. (Eunapius + carteri_)) from an aquarium in Calcutta (x 10). + + [Illustration: Freshwater Sponges. Plate I. + A. C. Chowdhary, del. SPONGILLA.] + + + + + PLATE II. + + PHOTOGRAPHS OF DRIED SPECIMENS OF _Spongilla_, _Tubella_, AND + _Corvospongilla_. + + + Fig. 1. Part of a large specimen of _S. (Eunapius) carteri_ + from Calcutta, to show the conspicuous rounded oscula + (reduced). + + Fig. 2. Gemmules of _S. (Stratospongilla) bombayensis_ on a + stone from the edge of Igatpuri Lake, Bombay Presidency + (nat. size). + + Fig. 3. Part of one of the type-specimens of _S. + (Stratospongilla) ultima_ from Cape Comorin, Travancore, to + show the star-shaped oscula (slightly enlarged). + + Fig. 4. Part of the type specimen of _T. vesparioides_ + (external membrane destroyed), to show the reticulate + skeleton and the numerous gemmules (nat. size). + + Fig. 5. Part of a schizotype of _C. burmanica_ to show the + elevated oscula (nat. size). + + [Illustration: Freshwater Sponges. Plate II. + Photo by A. Chowdhary. Spongilla, Tubella, Corvospongilla.] + + + + + PLATE III. + + PHOTOGRAPHS OF SPECIMENS OF _Plumatella_, _Lophopodella_, AND + _Pectinatella_. + + Fig. 1. Specimen in spirit of _P. fruticosa_ (typical + form) on the leaf of a bulrush from a pond in the Calcutta + Zoological Gardens (nat. size). + + Fig. 2. A small zoarium of the _benedeni_ phase of _P. + emarginata_ from Rangoon (nat. size). Part of the mass has + been removed at one end to show the structure. The specimen + was preserved in spirit. + + Fig. 3. Part of a large zoarium of _P. diffusa_ on a log + of wood from Gangtok, Sikhim (nat. size). An enlarged figure + of another part of the same specimen is given in fig. 2, Pl. + IV. The specimen was preserved in spirit. + + Figs. 4, 4 _a_. Specimens of _L. carteri_ from Igatpuri + Lake, Bombay, preserved in formalin. Fig. 4 represents a + mass of polyparia surrounded by a green gelatinous alga on + the stem of a water-plant; fig. 4_a_ an isolated polyparium + with the polypides fully expanded from the under surface of + a stone in the same lake. Both figures are of natural size. + + Fig. 5. Part of a compound colony of _P. burmanica_ on + the stem of a reed from the Sur Lake, Orissa (nat. size, + preserved in formalin). + + [Illustration: Phylactolaematous Polyzoa. Plate III. + Photo by A. Chowdhary. Plumatella, Lophopodella, Pectinatella.] + + + + + PLATE IV. + + SPECIMENS OF _Plumatella_. + + Fig. 1. Vertical branch of a polyparium of _P. emarginata_ + from Calcutta, to show method of branching (x 8). The + specimen was preserved in formalin, stained with haemalum, + and after dehydration and clearing, mounted in canada + balsam. + + Fig. 1 _a._ Part of a young, horizontal zoarium of _P. + emarginata_ from Rangoon (x 4, preserved in spirit). + + Fig. 2. Part of a zoarium of _P. diffusa_ from Gangtok, + Sikhim (x 4). See Pl. III, fig. 3. + + Figs. 3, 3 _a._ Specimens in spirit of _P. allmani_ from + Bhim Tal (lake), W. Himalayas. Fig. 3 represents a mature + polyparium; fig. 3 _a_ a young polyparium to which the + valves of the statoblast (x) whence it had arisen are still + attached. + + Fig. 4. Part of a zoarium of the _coralloides_ phase of _P. + fruticosa_ (from Calcutta) preserved in spirit, as seen on + the surface of the sponge in which it is embedded (x 3). + + Fig. 5. Part of the margin of a living polyparium of _P. + punctata_ from Calcutta (x 8) with the polypides fully + expanded. + + [Illustration: Phylactolaematous Polyzoa. Plate IV. + A. C. Chowdhary, del. PLUMATELLA.] + + + + + PLATE V. + + SPECIMENS OF _Plumatella_, _Stolella_, AND _Pectinatella_. + + Fig. 1. Part of a zoarium of the _coralloides_ phase of _P. + fruticosa_ (x 10) from Calcutta. The specimen, which was + preserved in spirit, had been removed from a sponge of + _Spongilla carteri_. + + Fig. 2. Terminal branch of a polyparium of _P. punctata_ + from Calcutta (x 30). The specimen was preserved in + formalin, stained with haematoxylin, and finally mounted in + canada balsam. + + Fig. 3. Part of an adult polyparium of _S. indica_ from + the United Provinces (x 30). The specimen was preserved in + formalin, stained with haemalum, and finally mounted in + canada balsam. The lower zooecium contains a mature free + statoblast, the upper one a fixed one. + + Fig. 4. The growing point of a young polyparium of the + same species from Calcutta (x 30), to show the method of + formation of the stolon that connects the different groups + of zooecia. The specimen had been treated in the same way as + that represented in fig. 3. + + Figs. 5, 5 _a_. Zoaria from a compound colony of _P. + burmanica_ from the Sur Lake, Orissa (x 2). The specimens, + which were preserved in formalin, are represented as seen + from the adherent surface of the colony. + + [Illustration: Phylactolaematous Polyzoa. Plate V. + A. C. Chowdhary, del. Plumatella, Stolella, Pectinatella.] + + + + + * * * * * + + + + +Transcriber's note: + + In the Systematic Index, sub-family items were renumbered from 15. + through 38., to correspond to the numbers used in the text of the + book. + Greek letters used as symbols are spelled out, e.g. alpha, beta, etc. + Letters missing or mis-typeset were inserted, e.g. 'practica ly' to + 'practically' + Footnotes were moved after the paragraph to which they pertain. + Raised dots were replaced with decimal points in numeric notations. + Bold page numbers in the index are surrounded by tildes, e.g. ~76~. + Punctuation was standardized. + Added a description of a sketch contained within one line of text. + + Other changes: + 'recognzied' to 'recognized' ... be recognized.... + 'benegalensis' to 'bengalensis' ... lacustris var. bengalensis,... + 'pecular' to 'peculiar' ... the peculiar amphipod ... + 'milar' to 'similar' ... similar in the two ... + 'large' to 'larger' ... a little larger than the upper ... + 'pennsylvania' to 'pennsylvanica' ...Tubella pennsylvanica... + 'variely' to 'variety' ... specimens of the variety ... + 'measurments' to 'measurements' ... the average measurements ... + 'It' to 'Its' ... Its buds, however, possessed ... + 'dispsition' to 'disposition' ... 'Y-shaped disposition of ... + 'Wood's Holl' to 'Wood's Hole' ... Biol. Bull. Wood's Hole,... + '1852' to '1851' at the end of the citation of Leidy's paper, to + match date at the beginning of the citation paragraph. + 'syoecium' to 'synoecium' ...in a gelatinous synoecium... + 'Lacustre' to lower case ...Ann. Biol. lacustre,... + 'Dactyloccopsis' to 'Dactylococcopsis' ... Dactylococcopsis + pectinatellophila ... + 'amphioxus' to 'amphioxous' ... amphistrongylous or amphioxous ... + 'Trida' and 'Trida' to 'Trida' for consistency ... Praze, Trida ... + + + +***END OF THE PROJECT GUTENBERG EBOOK FRESHWATER SPONGES, HYDROIDS & +POLYZOA*** + + +******* This file should be named 36504.txt or 36504.zip ******* + + +This and all associated files of various formats will be found in: +http://www.gutenberg.org/dirs/3/6/5/0/36504 + + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. Special rules, +set forth in the General Terms of Use part of this license, apply to +copying and distributing Project Gutenberg-tm electronic works to +protect the PROJECT GUTENBERG-tm concept and trademark. Project +Gutenberg is a registered trademark, and may not be used if you +charge for the eBooks, unless you receive specific permission. 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