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    <h1>
      THE PERPETUATION OF LIVING BEINGS, HEREDITARY TRANSMISSION AND VARIATION
    </h1>
    <p>
      <br />
    </p>
    <h3>
      Lecture III. (of VI.), "Lectures To Working Men", at the Museum of
      Practical Geology, 1863, On Darwin's work: "Origin of Species".
    </h3>
    <p>
      <br /><br />
    </p>
    <h2>
      By Thomas H. Huxley
    </h2>
    <p>
      <br /> <br />
    </p>
    <hr />
    <p>
      <br /> <br />
    </p>
    <p>
      The inquiry which we undertook, at our last meeting, into the state of our
      knowledge of the causes of the phenomena of organic nature,&mdash;of the
      past and of the present,&mdash;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.
    </p>
    <p>
      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.
    </p>
    <p>
      The method of the perpetuation of organic beings is of two kinds,&mdash;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,&mdash;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.
    </p>
    <p>
      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.
    </p>
    <p>
      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&mdash;as was shown by the Abbe
      Trembley many years ago&mdash;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.
    </p>
    <p>
      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&mdash;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.
    </p>
    <p>
      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,&mdash;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.
    </p>
    <p>
      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,&mdash;among them the Abbe
      Spallanzani, who made a number of experiments upon snails and salamanders,&mdash;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.
    </p>
    <p>
      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&mdash;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&mdash;it is called 'Atavism', it expresses this tendency to revert
      to the ancestral type, and comes from the Latin word 'atavus', ancestor.
    </p>
    <p>
      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.
    </p>
    <p>
      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.
    </p>
    <p>
      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&mdash;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.
    </p>
    <p>
      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&mdash;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,&mdash;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.
    </p>
    <p>
      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,&mdash;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&mdash;there is usually an important preponderance, but not
      always on the same side.
    </p>
    <p>
      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.
    </p>
    <p>
      Secondly, there is a variation, to a certain extent&mdash;though, in all
      probability, the influence of this cause has been very much exaggerated&mdash;but
      there is no doubt that variation is produced, to a certain extent, by what
      are commonly known as external conditions,&mdash;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,&mdash;in
      these there is nothing of the kind,&mdash;everything depends on previous
      conditions. But when we cannot trace the cause of phenomena, we call them
      spontaneous.
    </p>
    <p>
      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,&mdash;which
      was indeed a very curious essay,&mdash;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.
    </p>
    <p>
      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,&mdash;"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.
    </p>
    <p>
      Now let us go back to Atavism,&mdash;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.
    </p>
    <p>
      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.
    </p>
    <p>
      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.
    </p>
    <p>
      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.
    </p>
    <p>
      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&mdash;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&mdash;I
      suppose it was because they were so common&mdash;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.
    </p>
    <p>
      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,&mdash;then
      you may almost certainly produce a race whose tendency to continue the
      variation is exceedingly strong.
    </p>
    <p>
      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.
    </p>
    <p>
      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.
    </p>
    <p>
      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.
    </p>
    <p>
      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,&mdash;that all the most important races have
      arisen by this selective breeding from accidental variation.
    </p>
    <p>
      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,&mdash;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.
    </p>
    <p>
      Among the enormous variety,&mdash;I believe there are somewhere about a
      hundred and fifty kinds of pigeons,&mdash;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.
    </p>
    <p>
      The third kind I mentioned&mdash;the Fantail&mdash;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,&mdash;say thirty, or even
      more&mdash;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.
    </p>
    <p>
      But here is the last great variety,&mdash;the Tumbler; and of that great
      variety, one of the principal kinds, and one most prized, is the specimen
      represented here&mdash;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&mdash;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.
    </p>
    <p>
      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.
    </p>
    <p>
      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,&mdash;and I mention the fact because it has been disputed
      by what is assumed to be high authority,&mdash;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,&mdash;although they have no relation to each other, yet appear
      to go together,&mdash;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,&mdash;the size and shape of the eggs,&mdash;the nature of
      flight, and the powers of flight,&mdash;so-called "homing" birds having
      enormous flying powers; <a href="#linknote-1" name="linknoteref-1"
      id="linknoteref-1"><small>1</small></a> 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,&mdash;whether
      of instinct, or habit, or bony structure, or of plumage,&mdash;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.
    </p>
    <p>
      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.
    </p>
    <p>
      <a name="linknote-1" id="linknote-1">
      <!-- Note --></a>
    </p>
    <p class="foot">
      1 (<a href="#linknoteref-1">return</a>)<br /> [ 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,&mdash;"homing"
      birds,&mdash;and are consequently used as carriers, are not "carriers" in
      the fancy sense.]
    </p>
    <p>
      <br /><br /><br /><br />
    </p>
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