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+The Project Gutenberg EBook of The Perpetuation Of Living Beings,
+Hereditary Transmission And Variation, by Thomas H. Huxley
+
+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: The Perpetuation Of Living Beings, Hereditary Transmission And Variation
+       Lecture IV. (of VI.), Lectures To Working Men, at the
+       Museum of Practical Geology, 1863, On Darwin's work: "Origin
+       of Species".
+
+Author: Thomas H. Huxley
+
+Posting Date: January 4, 2009 [EBook #2924]
+Release Date: November, 2001
+
+Language: English
+
+Character set encoding: ASCII
+
+*** START OF THIS PROJECT GUTENBERG EBOOK HEREDITARY TRANSMISSION ***
+
+
+
+
+Produced by Amy E. Zelmer
+
+
+
+
+
+THE PERPETUATION OF LIVING BEINGS, HEREDITARY TRANSMISSION AND VARIATION
+
+By Thomas Henry Huxley
+
+
+
+
+The inquiry which we undertook, at our last meeting, into the state of
+our knowledge of the causes of the phenomena of organic nature,--of the
+past and of the present,--resolved itself into two subsidiary inquiries:
+the first was, whether we know anything, either historically or
+experimentally, of the mode of origin of living beings; the second
+subsidiary inquiry was, whether, granting the origin, we know anything
+about the perpetuation and modifications of the forms of organic beings.
+The reply which I had to give to the first question was altogether
+negative, and the chief result of my last lecture was, that, neither
+historically nor experimentally, do we at present know anything
+whatsoever about the origin of living forms. We saw that, historically,
+we are not likely to know anything about it, although we may perhaps
+learn something experimentally; but that at present we are an enormous
+distance from the goal I indicated.
+
+I now, then, take up the next question, What do we know of the
+reproduction, the perpetuation, and the modifications of the forms
+of living beings, supposing that we have put the question as to their
+origination on one side, and have assumed that at present the causes of
+their origination are beyond us, and that we know nothing about them?
+Upon this question the state of our knowledge is extremely different; it
+is exceedingly large, and, if not complete, our experience is certainly
+most extensive. It would be impossible to lay it all before you, and the
+most I can do, or need do to-night, is to take up the principal points
+and put them before you with such prominence as may subserve the
+purposes of our present argument.
+
+The method of the perpetuation of organic beings is of two kinds,--the
+asexual and the sexual. In the first the perpetuation takes place from
+and by a particular act of an individual organism, which sometimes may
+not be classed as belonging to any sex at all. In the second case, it is
+in consequence of the mutual action and interaction of certain portions
+of the organisms of usually two distinct individuals,--the male and the
+female. The cases of asexual perpetuation are by no means so common as
+the cases of sexual perpetuation; and they are by no means so common in
+the animal as in the vegetable world. You are all probably familiar with
+the fact, as a matter of experience, that you can propagate plants
+by means of what are called "cuttings;" for example, that by taking a
+cutting from a geranium plant, and rearing it properly, by supplying it
+with light and warmth and nourishment from the earth, it grows up
+and takes the form of its parent, having all the properties and
+peculiarities of the original plant.
+
+Sometimes this process, which the gardener performs artificially, takes
+place naturally; that is to say, a little bulb, or portion of the plant,
+detaches itself, drops off, and becomes capable of growing as a separate
+thing. That is the case with many bulbous plants, which throw off in
+this way secondary bulbs, which are lodged in the ground and become
+developed into plants. This is an asexual process, and from it results
+the repetition or reproduction of the form of the original being from
+which the bulb proceeds.
+
+Among animals the same thing takes place. Among the lower forms of
+animal life, the infusorial animalculae we have already spoken of throw
+off certain portions, or break themselves up in various directions,
+sometimes transversely or sometimes longitudinally; or they may give off
+buds, which detach themselves and develop into their proper forms. There
+is the common fresh-water Polype, for instance, which multiplies itself
+in this way. Just in the same way as the gardener is able to multiply
+and reproduce the peculiarities and characters of particular plants
+by means of cuttings, so can the physiological experimentalist--as was
+shown by the Abbe Trembley many years ago--so can he do the same thing
+with many of the lower forms of animal life. M. de Trembley showed that
+you could take a polype and cut it into two, or four, or many pieces,
+mutilating it in all directions, and the pieces would still grow up
+and reproduce completely the original form of the animal. These are
+all cases of asexual multiplication, and there are other instances,
+and still more extraordinary ones, in which this process takes place
+naturally, in a more hidden, a more recondite kind of way. You are all
+of you familiar with those little green insects, the 'Aphis' or blight,
+as it is called. These little animals, during a very considerable part
+of their existence, multiply themselves by means of a kind of internal
+budding, the buds being developed into essentially asexual animals,
+which are neither male nor female; they become converted into young
+'Aphides', which repeat the process, and their offspring after them,
+and so on again; you may go on for nine or ten, or even twenty or more
+successions; and there is no very good reason to say how soon it might
+terminate, or how long it might not go on if the proper conditions of
+warmth and nourishment were kept up.
+
+Sexual reproduction is quite a distinct matter. Here, in all these
+cases, what is required is the detachment of two portions of the
+parental organisms, which portions we know as the egg and the
+spermatozoon. In plants it is the ovule and the pollen-grain, as in
+the flowering plants, or the ovule and the antherozooid, as in the
+flowerless. Among all forms of animal life, the spermatozoa proceed from
+the male sex, and the egg is the product of the female. Now, what is
+remarkable about this mode of reproduction is this, that the egg by
+itself, or the spermatozoa by themselves, are unable to assume the
+parental form; but if they be brought into contact with one another, the
+effect of the mixture of organic substances proceeding from two sources
+appears to confer an altogether new vigour to the mixed product. This
+process is brought about, as we all know, by the sexual intercourse of
+the two sexes, and is called the act of impregnation. The result of this
+act on the part of the male and female is, that the formation of a new
+being is set up in the ovule or egg; this ovule or egg soon begins to
+be divided and subdivided, and to be fashioned into various complex
+organisms, and eventually to develop into the form of one of its
+parents, as I explained in the first lecture. These are the processes by
+which the perpetuation of organic beings is secured. Why there should be
+the two modes--why this re-invigoration should be required on the part
+of the female element we do not know; but it is most assuredly the
+fact, and it is presumable, that, however long the process of asexual
+multiplication could be continued, I say there is good reason to believe
+that it would come to an end if a new commencement were not obtained by
+a conjunction of the two sexual elements.
+
+That character which is common to these two distinct processes is
+this, that, whether we consider the reproduction, or perpetuation, or
+modification of organic beings as they take place asexually, or as they
+may take place sexually,--in either case, I say, the offspring has a
+constant tendency to assume, speaking generally, the character of the
+parent. As I said just now, if you take a slip of a plant, and tend it
+with care, it will eventually grow up and develop into a plant like
+that from which it had sprung; and this tendency is so strong that, as
+gardeners know, this mode of multiplying by means of cuttings is the
+only secure mode of propagating very many varieties of plants; the
+peculiarity of the primitive stock seems to be better preserved if you
+propagate it by means of a slip than if you resort to the sexual mode.
+
+Again, in experiments upon the lower animals, such as the polype, to
+which I have referred, it is most extraordinary that, although cut up
+into various pieces, each particular piece will grow up into the form of
+the primitive stock; the head, if separated, will reproduce the body
+and the tail; and if you cut off the tail, you will find that that will
+reproduce the body and all the rest of the members, without in any way
+deviating from the plan of the organism from which these portions have
+been detached. And so far does this go, that some experimentalists have
+carefully examined the lower orders of animals,--among them the
+Abbe Spallanzani, who made a number of experiments upon snails and
+salamanders,--and have found that they might mutilate them to an
+incredible extent; that you might cut off the jaw or the greater part
+of the head, or the leg or the tail, and repeat the experiment several
+times, perhaps, cutting off the same member again and again; and yet
+each of those types would be reproduced according to the primitive type:
+nature making no mistake, never putting on a fresh kind of leg, or head,
+or tail, but always tending to repeat and to return to the primitive
+type.
+
+It is the same in sexual reproduction: it is a matter of perfectly
+common experience, that the tendency on the part of the offspring always
+is, speaking broadly, to reproduce the form of the parents. The
+proverb has it that the thistle does not bring forth grapes; so, among
+ourselves, there is always a likeness, more or less marked and distinct,
+between children and their parents. That is a matter of familiar and
+ordinary observation. We notice the same thing occurring in the cases
+of the domestic animals--dogs, for instance, and their offspring. In
+all these cases of propagation and perpetuation, there seems to be
+a tendency in the offspring to take the characters of the parental
+organisms. To that tendency a special name is given--it is called
+'Atavism', it expresses this tendency to revert to the ancestral type,
+and comes from the Latin word 'atavus', ancestor.
+
+Well, this 'Atavism' which I shall speak of, is, as I said before, one
+of the most marked and striking tendencies of organic beings; but, side
+by side with this hereditary tendency there is an equally distinct and
+remarkable tendency to variation. The tendency to reproduce the original
+stock has, as it were, its limits, and side by side with it there is a
+tendency to vary in certain directions, as if there were two opposing
+powers working upon the organic being, one tending to take it in a
+straight line, and the other tending to make it diverge from that
+straight line, first to one side and then to the other.
+
+So that you see these two tendencies need not precisely contradict one
+another, as the ultimate result may not always be very remote from what
+would have been the case if the line had been quite straight.
+
+This tendency to variation is less marked in that mode of propagation
+which takes place asexually; it is in that mode that the minor
+characters of animal and vegetable structures are most completely
+preserved. Still, it will happen sometimes, that the gardener, when he
+has planted a cutting of some favourite plant, will find, contrary to
+his expectation, that the slip grows up a little different from the
+primitive stock--that it produces flowers of a different colour or make,
+or some deviation in one way or another. This is what is called the
+'sporting' of plants.
+
+In animals the phenomena of asexual propagation are so obscure, that
+at present we cannot be said to know much about them; but if we turn to
+that mode of perpetuation which results from the sexual process, then
+we find variation a perfectly constant occurrence, to a certain extent;
+and, indeed, I think that a certain amount of variation from the
+primitive stock is the necessary result of the method of sexual
+propagation itself; for, inasmuch as the thing propagated proceeds from
+two organisms of different sexes and different makes and temperaments,
+and as the offspring is to be either of one sex or the other, it is
+quite clear that it cannot be an exact diagonal of the two, or it would
+be of no sex at all; it cannot be an exact intermediate form between
+that of each of its parents--it must deviate to one side or the other.
+You do not find that the male follows the precise type of the male
+parent, nor does the female always inherit the precise characteristics
+of the mother,--there is always a proportion of the female character in
+the male offspring, and of the male character in the female offspring.
+That must be quite plain to all of you who have looked at all
+attentively on your own children or those of your neighbours; you will
+have noticed how very often it may happen that the son shall exhibit the
+maternal type of character, or the daughter possess the characteristics
+of the father's family. There are all sorts of intermixtures and
+intermediate conditions between the two, where complexion, or beauty,
+or fifty other different peculiarities belonging to either side of the
+house, are reproduced in other members of the same family. Indeed, it
+is sometimes to be remarked in this kind of variation, that the variety
+belongs, strictly speaking, to neither of the immediate parents; you
+will see a child in a family who is not like either its father or its
+mother; but some old person who knew its grandfather or grandmother, or,
+it may be, an uncle, or, perhaps, even a more distant relative, will see
+a great similarity between the child and one of these. In this way it
+constantly happens that the characteristic of some previous member
+of the family comes out and is reproduced and recognised in the most
+unexpected manner.
+
+But apart from that matter of general experience, there are some cases
+which put that curious mixture in a very clear light. You are aware that
+the offspring of the Ass and the Horse, or rather of the he-Ass and the
+Mare, is what is called a Mule; and, on the other hand, the offspring
+of the Stallion and the she-Ass is what is called a 'Hinny'. I never saw
+one myself; but they have been very carefully studied. Now, the
+curious thing is this, that although you have the same elements in
+the experiment in each case, the offspring is entirely different in
+character, according as the male influence comes from the Ass or the
+Horse. Where the Ass is the male, as in the case of the Mule, you find
+that the head is like that of the Ass, that the ears are long, the
+tail is tufted at the end, the feet are small, and the voice is an
+unmistakable bray; these are all points of similarity to the Ass; but,
+on the other hand, the barrel of the body and the cut of the neck are
+much more like those of the Mare. Then, if you look at the Hinny,--the
+result of the union of the Stallion and the she-Ass, then you find it is
+the Horse that has the predominance; that the head is more like that
+of the Horse, the ears are shorter, the legs coarser, and the type is
+altogether altered; while the voice, instead of being a bray, is the
+ordinary neigh of the Horse. Here, you see, is a most curious thing: you
+take exactly the same elements, Ass and Horse, but you combine the sexes
+in a different manner, and the result is modified accordingly. You
+have in this case, however, a result which is not general and
+universal--there is usually an important preponderance, but not always
+on the same side.
+
+Here, then, is one intelligible, and, perhaps, necessary cause of
+variation: the fact, that there are two sexes sharing in the production
+of the offspring, and that the share taken by each is different and
+variable, not only for each combination, but also for different members
+of the same family.
+
+Secondly, there is a variation, to a certain extent--though, in
+all probability, the influence of this cause has been very much
+exaggerated--but there is no doubt that variation is produced, to a
+certain extent, by what are commonly known as external conditions,--such
+as temperature, food, warmth, and moisture. In the long run, every
+variation depends, in some sense, upon external conditions, seeing that
+everything has a cause of its own. I use the term "external conditions"
+now in the sense in which it is ordinarily employed: certain it is, that
+external conditions have a definite effect. You may take a plant which
+has single flowers, and by dealing with the soil, and nourishment, and
+so on, you may by-and-by convert single flowers into double flowers,
+and make thorns shoot out into branches. You may thicken or make various
+modifications in the shape of the fruit. In animals, too, you may
+produce analogous changes in this way, as in the case of that deep
+bronze colour which persons rarely lose after having passed any length
+of time in tropical countries. You may also alter the development of
+the muscles very much, by dint of training; all the world knows that
+exercise has a great effect in this way; we always expect to find the
+arm of a blacksmith hard and wiry, and possessing a large development
+of the brachial muscles. No doubt training, which is one of the forms
+of external conditions, converts what are originally only instructions,
+teachings, into habits, or, in other words, into organizations, to a
+great extent; but this second cause of variation cannot be considered
+to be by any means a large one. The third cause that I have to mention,
+however, is a very extensive one. It is one that, for want of a better
+name, has been called "spontaneous variation;" which means that when
+we do not know anything about the cause of phenomena, we call it
+spontaneous. In the orderly chain of causes and effects in this world,
+there are very few things of which it can be said with truth that they
+are spontaneous. Certainly not in these physical matters,--in
+these there is nothing of the kind,--everything depends on previous
+conditions. But when we cannot trace the cause of phenomena, we call
+them spontaneous.
+
+Of these variations, multitudinous as they are, but little is known with
+perfect accuracy. I will mention to you some two or three cases, because
+they are very remarkable in themselves, and also because I shall want to
+use them afterwards. Reaumur, a famous French naturalist, a great
+many years ago, in an essay which he wrote upon the art of hatching
+chickens,--which was indeed a very curious essay,--had occasion to speak
+of variations and monstrosities. One very remarkable case had come under
+his notice of a variation in the form of a human member, in the person
+of a Maltese, of the name of Gratio Kelleia, who was born with six
+fingers upon each hand, and the like number of toes to each of his feet.
+That was a case of spontaneous variation. Nobody knows why he was born
+with that number of fingers and toes, and as we don't know, we call it a
+case of "spontaneous" variation. There is another remarkable case also.
+I select these, because they happen to have been observed and noted very
+carefully at the time. It frequently happens that a variation occurs,
+but the persons who notice it do not take any care in noting down the
+particulars, until at length, when inquiries come to be made, the exact
+circumstances are forgotten; and hence, multitudinous as may be such
+"spontaneous" variations, it is exceedingly difficult to get at the
+origin of them.
+
+The second case is one of which you may find the whole details in the
+"Philosophical Transactions" for the year 1813, in a paper communicated
+by Colonel Humphrey to the President of the Royal Society,--"On a new
+Variety in the Breed of Sheep," giving an account of a very remarkable
+breed of sheep, which at one time was well known in the northern states
+of America, and which went by the name of the Ancon or the Otter breed
+of sheep. In the year 1791, there was a farmer of the name of Seth
+Wright in Massachusetts, who had a flock of sheep, consisting of a ram
+and, I think, of some twelve or thirteen ewes. Of this flock of ewes,
+one at the breeding-time bore a lamb which was very singularly formed;
+it had a very long body, very short legs, and those legs were bowed!
+I will tell you by-and-by how this singular variation in the breed of
+sheep came to be noted, and to have the prominence that it now has. For
+the present, I mention only these two cases; but the extent of variation
+in the breed of animals is perfectly obvious to any one who has studied
+natural history with ordinary attention, or to any person who compares
+animals with others of the same kind. It is strictly true that there are
+never any two specimens which are exactly alike; however similar, they
+will always differ in some certain particular.
+
+Now let us go back to Atavism,--to the hereditary tendency I spoke
+of. What will come of a variation when you breed from it, when Atavism
+comes, if I may say so, to intersect variation? The two cases of which
+I have mentioned the history, give a most excellent illustration of
+what occurs. Gratio Kelleia, the Maltese, married when he was twenty-two
+years of age, and, as I suppose there were no six-fingered ladies in
+Malta, he married an ordinary five-fingered person. The result of that
+marriage was four children; the first, who was christened Salvator, had
+six fingers and six toes, like his father; the second was George, who
+had five fingers and toes, but one of them was deformed, showing a
+tendency to variation; the third was Andre; he had five fingers and five
+toes, quite perfect; the fourth was a girl, Marie; she had five fingers
+and five toes, but her thumbs were deformed, showing a tendency toward
+the sixth.
+
+These children grew up, and when they came to adult years, they all
+married, and of course it happened that they all married five-fingered
+and five-toed persons. Now let us see what were the results. Salvator
+had four children; they were two boys, a girl, and another boy; the
+first two boys and the girl were six-fingered and six-toed like their
+grandfather; the fourth boy had only five fingers and five toes. George
+had only four children; there were two girls with six fingers and six
+toes; there was one girl with six fingers and five toes on the right
+side, and five fingers and five toes on the left side, so that she was
+half and half. The last, a boy, had five fingers and five toes. The
+third, Andre, you will recollect, was perfectly well-formed, and he had
+many children whose hands and feet were all regularly developed. Marie,
+the last, who, of course, married a man who had only five fingers, had
+four children; the first, a boy, was born with six toes, but the other
+three were normal.
+
+Now observe what very extraordinary phenomena are presented here.
+You have an accidental variation arising from what you may call a
+monstrosity; you have that monstrosity tendency or variation diluted in
+the first instance by an admixture with a female of normal construction,
+and you would naturally expect that, in the results of such an union,
+the monstrosity, if repeated, would be in equal proportion with the
+normal type; that is to say, that the children would be half and half,
+some taking the peculiarity of the father, and the others being of
+the purely normal type of the mother; but you see we have a great
+preponderance of the abnormal type. Well, this comes to be mixed once
+more with the pure, the normal type, and the abnormal is again produced
+in large proportion, notwithstanding the second dilution. Now what would
+have happened if these abnormal types had intermarried with each other;
+that is to say, suppose the two boys of Salvator had taken it into their
+heads to marry their first cousins, the two first girls of George, their
+uncle? You will remember that these are all of the abnormal type of
+their grandfather. The result would probably have been, that their
+offspring would have been in every case a further development of that
+abnormal type. You see it is only in the fourth, in the person of
+Marie, that the tendency, when it appears but slightly in the second
+generation, is washed out in the third, while the progeny of Andre, who
+escaped in the first instance, escape altogether.
+
+We have in this case a good example of nature's tendency to the
+perpetuation of a variation. Here it is certainly a variation which
+carried with it no use or benefit; and yet you see the tendency to
+perpetuation may be so strong, that, notwithstanding a great admixture
+of pure blood, the variety continues itself up to the third generation,
+which is largely marked with it. In this case, as I have said, there
+was no means of the second generation intermarrying with any but
+five-fingered persons, and the question naturally suggests itself, What
+would have been the result of such marriage? Reaumur narrates this case
+only as far as the third generation. Certainly it would have been
+an exceedingly curious thing if we could have traced this matter any
+further; had the cousins intermarried, a six-fingered variety of the
+human race might have been set up.
+
+To show you that this supposition is by no means an unreasonable one,
+let me now point out what took place in the case of Seth Wright's sheep,
+where it happened to be a matter of moment to him to obtain a breed
+or raise a flock of sheep like that accidental variety that I have
+described--and I will tell you why. In that part of Massachusetts where
+Seth Wright was living, the fields were separated by fences, and the
+sheep, which were very active and robust, would roam abroad, and without
+much difficulty jump over these fences into other people's farms. As
+a matter of course, this exuberant activity on the part of the
+sheep constantly gave rise to all sorts of quarrels, bickerings, and
+contentions among the farmers of the neighbourhood; so it occurred to
+Seth Wright, who was, like his successors, more or less 'cute, that if
+he could get a stock of sheep like those with the bandy legs, they would
+not be able to jump over the fences so readily, and he acted upon that
+idea. He killed his old ram, and as soon as the young one arrived at
+maturity, he bred altogether from it. The result was even more striking
+than in the human experiment which I mentioned just now. Colonel
+Humphreys testifies that it always happened that the offspring were
+either pure Ancons or pure ordinary sheep; that in no case was there
+any mixing of the Ancons with the others. In consequence of this, in
+the course of a very few years, the farmer was able to get a very
+considerable flock of this variety, and a large number of them were
+spread throughout Massachusetts. Most unfortunately, however--I suppose
+it was because they were so common--nobody took enough notice of them to
+preserve their skeletons; and although Colonel Humphreys states that he
+sent a skeleton to the President of the Royal Society at the same time
+that he forwarded his paper, I am afraid that the variety has entirely
+disappeared; for a short time after these sheep had become prevalent in
+that district, the Merino sheep were introduced; and as their wool was
+much more valuable, and as they were a quiet race of sheep, and showed
+no tendency to trespass or jump over fences, the Otter breed of sheep,
+the wool of which was inferior to that of the Merino, was gradually
+allowed to die out.
+
+You see that these facts illustrate perfectly well what may be done if
+you take care to breed from stocks that are similar to each other. After
+having got a variation, if, by crossing a variation with the original
+stock, you multiply that variation, and then take care to keep that
+variation distinct from the original stock, and make them breed
+together,--then you may almost certainly produce a race whose tendency
+to continue the variation is exceedingly strong.
+
+This is what is called "selection"; and it is by exactly the same
+process as that by which Seth Wright bred his Ancon sheep, that
+our breeds of cattle, dogs, and fowls, are obtained. There are some
+possibilities of exception, but still, speaking broadly, I may say that
+this is the way in which all our varied races of domestic animals have
+arisen; and you must understand that it is not one peculiarity or one
+characteristic alone in which animals may vary. There is not a single
+peculiarity or characteristic of any kind, bodily or mental, in which
+offspring may not vary to a certain extent from the parent and other
+animals.
+
+Among ourselves this is well known. The simplest physical peculiarity is
+mostly reproduced. I know a case of a man whose wife has the lobe of
+one of her ears a little flattened. An ordinary observer might scarcely
+notice it, and yet every one of her children has an approximation to the
+same peculiarity to some extent. If you look at the other extreme, too,
+the gravest diseases, such as gout, scrofula, and consumption, may be
+handed down with just the same certainty and persistence as we noticed
+in the perpetuation of the bandy legs of the Ancon sheep.
+
+However, these facts are best illustrated in animals, and the extent
+of the variation, as is well known, is very remarkable in dogs. For
+example, there are some dogs very much smaller than others; indeed, the
+variation is so enormous that probably the smallest dog would be about
+the size of the head of the largest; there are very great variations in
+the structural forms not only of the skeleton but also in the shape of
+the skull, and in the proportions of the face and the disposition of the
+teeth.
+
+The Pointer, the Retriever, Bulldog, and the Terrier, differ very
+greatly, and yet there is every reason to believe that every one
+of these races has arisen from the same source,--that all the most
+important races have arisen by this selective breeding from accidental
+variation.
+
+A still more striking case of what may be done by selective breeding,
+and it is a better case, because there is no chance of that partial
+infusion of error to which I alluded, has been studied very carefully by
+Mr. Darwin,--the case of the domestic pigeons. I dare say there may
+be some among you who may be pigeon 'fanciers', and I wish you to
+understand that in approaching the subject, I would speak with all
+humility and hesitation, as I regret to say that I am not a pigeon
+fancier. I know it is a great art and mystery, and a thing upon which
+a man must not speak lightly; but I shall endeavour, as far as
+my understanding goes, to give you a summary of the published and
+unpublished information which I have gained from Mr. Darwin.
+
+Among the enormous variety,--I believe there are somewhere about a
+hundred and fifty kinds of pigeons,--there are four kinds which may
+be selected as representing the extremest divergences of one kind from
+another. Their names are the Carrier, the Pouter, the Fantail, and
+the Tumbler. In the large diagrams they are each represented in their
+relative sizes to each other. This first one is the Carrier; you will
+notice this large excrescence on its beak; it has a comparatively small
+head; there is a bare space round the eyes; it has a long neck, a very
+long beak, very strong legs, large feet, long wings, and so on. The
+second one is the Pouter, a very large bird, with very long legs and
+beak. It is called the Pouter because it is in the habit of causing its
+gullet to swell up by inflating it with air. I should tell you that all
+pigeons have a tendency to do this at times, but in the Pouter it is
+carried to an enormous extent. The birds appear to be quite proud of
+their power of swelling and puffing themselves out in this way; and I
+think it is about as droll a sight as you can well see to look at a
+cage full of these pigeons puffing and blowing themselves out in this
+ridiculous manner.
+
+The third kind I mentioned--the Fantail--is a small bird, with
+exceedingly small legs and a very small beak. It is most curiously
+distinguished by the size and extent of its tail, which, instead of
+containing twelve feathers, may have many more,--say thirty, or even
+more--I believe there are some with as many as forty-two. This bird has
+a curious habit of spreading out the feathers of its tail in such a
+way that they reach forward, and touch its head; and if this can be
+accomplished, I believe it is looked upon as a point of great beauty.
+
+But here is the last great variety,--the Tumbler; and of that great
+variety, one of the principal kinds, and one most prized, is the
+specimen represented here--the short-faced Tumbler. Its beak is reduced
+to a mere nothing. Just compare the beak of this one and that of the
+first one, the Carrier--I believe the orthodox comparison of the head
+and beak of a thoroughly well-bred Tumbler is to stick an oat into a
+cherry, and that will give you the proper relative proportions of the
+head and beak. The feet and legs are exceedingly small, and the bird
+appears to be quite a dwarf when placed side by side with this great
+Carrier.
+
+These are differences enough in regard to their external appearance; but
+these differences are by no means the whole or even the most important
+of the differences which obtain between these birds. There is hardly
+a single point of their structure which has not become more or less
+altered; and to give you an idea of how extensive these alterations
+are, I have here some very good skeletons, for which I am indebted to my
+friend, Mr. Tegetmeier, a great authority in these matters; by means
+of which, if you examine them by-and-by, you will be able to see the
+enormous difference in their bony structures.
+
+I had the privilege, some time ago, of access to some important MSS. of
+Mr. Darwin, who, I may tell you, has taken very great pains and
+spent much valuable time and attention on the investigation of these
+variations, and getting together all the facts that bear upon them.
+I obtained from these MSS. the following summary of the differences
+between the domestic breeds of pigeons; that is to say, a notification
+of the various points in which their organization differs. In the first
+place, the back of the skull may differ a good deal, and the development
+of the bones of the face may vary a great deal; the back varies a good
+deal; the shape of the lower jaw varies; the tongue varies very greatly,
+not only in correlation to the length and size of the beak, but it seems
+also to have a kind of independent variation of its own. Then the amount
+of naked skin round the eyes, and at the base of the beak, may vary
+enormously; so may the length of the eyelids, the shape of the nostrils,
+and the length of the neck. I have already noticed the habit of blowing
+out the gullet, so remarkable in the Pouter, and comparatively so in the
+others. There are great differences, too, in the size of the female and
+the male, the shape of the body, the number and width of the processes
+of the ribs, the development of the ribs, and the size, shape, and
+development of the breastbone. We may notice, too,--and I mention
+the fact because it has been disputed by what is assumed to be high
+authority,--the variation in the number of the sacral vertebrae. The
+number of these varies from eleven to fourteen, and that without any
+diminution in the number of the vertebrae of the back or of the tail.
+Then the number and position of the tail-feathers may vary enormously,
+and so may the number of the primary and secondary feathers of the
+wings. Again, the length of the feet and of the beak,--although they
+have no relation to each other, yet appear to go together,--that is, you
+have a long beak wherever you have long feet. There are differences also
+in the periods of the acquirement of the perfect plumage,--the size
+and shape of the eggs,--the nature of flight, and the powers of
+flight,--so-called "homing" birds having enormous flying powers; [1]
+while, on the other hand, the little Tumbler is so called because of its
+extraordinary faculty of turning head over heels in the air, instead of
+pursuing a direct course. And, lastly, the dispositions and voices of
+the birds may vary. Thus the case of the pigeons shows you that there
+is hardly a single particular,--whether of instinct, or habit, or
+bony structure, or of plumage,--of either the internal economy or the
+external shape, in which some variation or change may not take place,
+which, by selective breeding, may become perpetuated, and form the
+foundation of, and give rise to, a new race.
+
+[Footnote 1: The "Carrier," I learn from Mr. Tegetmeier, does not
+'carry'; a high-bred bird of this breed being but a poor flier. The
+birds which fly long distances, and come home,--"homing" birds,--and are
+consequently used as carriers, are not "carriers" in the fancy sense.]
+
+If you carry in your mind's eye these four varieties of pigeons, you
+will bear with you as good a notion as you can have, perhaps, of the
+enormous extent to which a deviation from a primitive type may be
+carried by means of this process of selective breeding.
+
+
+
+
+
+End of the Project Gutenberg EBook of The Perpetuation Of Living Beings,
+Hereditary Transmission And Variation, by Thomas H. Huxley
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