 This is a LibriVox recording. All LibriVox recordings are in the public domain. For more information or to volunteer, please visit LibriVox.org. Recorded by Annie Coleman in St. Louis, Missouri in April 2006. The Origin of Species by Means of Natural Selection. Or The Preservation of Favored Races and the Struggle for Life. Sixth London Edition by Charles Darwin. Introduction When on board HMS Beagle as a naturalist, I was much struck with certain facts in the distribution of the organic beings inhabiting South America and in the geological relations of the present to the past inhabitants of that continent. These facts, as will be seen in the latter chapters of this volume, seem to throw some light on the origin of species, that mystery of mysteries as it has been called by one of our greatest philosophers. On my return home it occurred to me in 1837 that something might perhaps be made out on this question by patiently accumulating and reflecting on all sorts of facts which could possibly have any bearing on it. After five years' work I allowed myself to speculate on the subject and drew up some short notes. These I enlarged in 1844 into a sketch of the conclusions which then seemed to me probable. From that period to the present day I have steadily pursued the same object. I hope that I may be excused for entering on these personal details as I give them to show that I have not been hasty in coming to a decision. My work is now, 1859, nearly finished, but as it will take me many more years to complete it and as my health is far from strong I have been urged to publish this abstract. I have more especially been induced to do this as Mr. Wallace, who is now studying the natural history of the Malay archipelago, has arrived at almost exactly the same general conclusions that I have on the origin of species. In 1858 he sent me a memoir on this subject with a request that I would forward it to Sir Charles Lyell, who sent it to the Linnean Society, and it is published in the third volume of the Journal of that Society. Sir C. Lyell and Dr. Hooker, who both knew of my work, the latter having read my sketch of 1844, honored me by thinking it advisable to publish, with Mr. Wallace's excellent memoir, some brief extracts from my manuscripts. This abstract, which I now publish, must necessarily be imperfect. I cannot here give references and authorities for my several statements, and I must trust to the reader, reposing some confidence in my accuracy. No doubt errors may have crept in, though I hope I have always been cautious and trusting to good authorities alone. I can here give only the general conclusions at which I have arrived, with a few facts and illustration, but which I hope in most cases will suffice. No one can feel more sensible than I do of the necessity of hereafter publishing in detail all the facts, with references, on which my conclusions have been grounded, and I hope in a future work to do this. For I am well aware that scarcely a single point is discussed in this volume on which facts cannot be adduced. Often apparently leading to conclusions directly opposite to those at which I have arrived. A fair result can be obtained only by fully stating and balancing the facts and arguments on both sides of each question, and this is here impossible. I much regret that want of space prevents my having the satisfaction of acknowledging the generous assistance which I have received from very many naturalists, some of them personally unknown to me. I cannot, however, let this opportunity pass without expressing my deep obligations to Dr. Hooker, who, for the last fifteen years, has aided me in every possible way by his large stores of knowledge and his excellent judgment. In considering the origin of species, it is quite conceivable that a naturalist, reflecting on the mutual affinities of organic beings, in their embryological relations, their geographical distribution, geological succession, and other such facts, might come to the conclusion that species had not been independently created, but had descended, like varieties, from other species. Nevertheless, such a conclusion, even if well founded, would be unsatisfactory, until it could be shown how the innumerable species inhabiting this world have been modified, so as to acquire that perfection of structure and co-adaptation which justly excites our admiration. Naturalists continually refer to external conditions, such as climate, food, etc., as the only possible cause of variation. In one limited sense, as we shall hereafter see, this may be true, but it is preposterous to attribute to mere external conditions the structure, for instance of the woodpecker, with its feet, tail, beak, and tongue, so admirably adapted to catch insects under the bark of trees. In the case of the mistletoe, which draws its nourishment from certain trees, which has seeds that must be transported by certain birds, and which has flowers with separate sexes absolutely requiring the agency of certain insects to bring pollen from one flower to the other, it is equally preposterous to account for the structure of this parasite with its relations to several distinct organic beings by the effects of external conditions, or of habit, or of the volition of the plant itself. It is therefore of the highest importance to gain a clear insight into the means of modification and co-adaptation. At the commencement of my observations, it seemed to me probable that a careful study of domesticated animals and of cultivated plants would offer the best chance of making out this obscure problem. Nor have I been disappointed in this and in all other perplexing cases I have invariably found that our knowledge, imperfect though it may be, of variation under domestication, afforded the best and safest clue. I may venture to express my conviction of the high value of such studies, although they have been very commonly neglected by naturalists. From these considerations I shall devote the first chapter of this abstract to variation under domestication. We shall thus see that a large amount of hereditary modification is at least possible, and what is equally or more important, we shall see how great is the power of man in accumulating by his selection successive slight variations. I will then pass on to the variability of species in a state of nature, but I shall, unfortunately, be compelled to treat this subject far too briefly, as it can be treated properly only by giving long catalogues of facts. We shall, however, be enabled to discuss what circumstances are most favorable to variation. In the next chapter, the struggle for existence among all organic beings throughout the world, which inevitably follows from the high geometrical ratio of their increase, will be considered. This is the doctrine of Malthus, applied to the whole animal and vegetable kingdoms. As many more individuals of each species are born that can possibly survive, and as, consequently, there is a frequently recurring struggle for existence, which follows that any being, if it vary however slightly in any manner profitable to itself, under the complex and sometimes varying conditions of life, will have a better chance of surviving, and thus be naturally selected. From the strong principle of inheritance, any selected variety will tend to propagate its new and modified form. This fundamental subject of natural selection will be treated at some length in the fourth chapter, and we shall then see how natural selection almost inevitably causes much extinction of the less improved forms of life, and leads to what I have called divergence of character. In the next chapter I shall discuss the complex and little-known laws of variation. In the five succeeding chapters, the most apparent and gravest difficulties in accepting the theory will be given. Namely, first, the difficulties of transitions, or how a simple being, or a simple organ, can be changed and perfected into a highly developed being, or into an elaborately constructed organ. Secondly, the subject of instinct, or the mental powers of animals. Thirdly, hybridism, or the infertility of species, and the fertility of varieties when intercrossed. And fourthly, the imperfection of the geological record. In the next chapter I shall consider the geological succession of organic beings throughout time. In the 12th and 13th, there geographical distribution throughout space. In the 14th, there classification, or mutual affinities, both when mature and in an embryonic condition. In the last chapter I shall give a brief recapitulation of the whole work, and a few concluding remarks. No one ought to feel surprised at much remaining as yet unexplained in regard to the origin of species and varieties, if he make due allowance for our profound ignorance in regard to the mutual relations of the many beings which live around us. Who can explain why one's species ranges widely and is very numerous, and why another allied species has a narrow range and is rare? Yet these relations are of the highest importance, for they determine the present welfare, and, as I believe, the future success and modification of every inhabitant of this world. Still less do we know of the mutual relations of the innumerable inhabitants of the world during the many past geological epochs in its history. Although much remains obscure, and will long remain obscure, I can entertain no doubt after the most deliberate study and dispassionate judgment of which I am capable, that the view which most naturalists until recently entertained, and which I formerly entertained, namely that each species has been independently created, is erroneous. I am fully convinced that species are not immutable, but that those belonging to what are called the same genera are lineal descendants of some other and generally extinct species, in the same manner as the acknowledged varieties of any one species are the descendants of that species. Furthermore, I am convinced that natural selection has been the most important, but not the exclusive means of modification. End of introduction. Chapter 1 Part A Variation under domestication Contents of this chapter include Causes of variability Effects of habit and the use and disuse of parts Correlated variation Inheritance Character of domestic varieties Difficulty of distinguishing between varieties and species Origin of domestic varieties from one or more species Domestic pigeons, their differences and origin Principles of selection anciently followed their effects Methodical and unconscious selection Unknown origin of our domestic productions Circumstances favorable to man's power of selection End of contents Causes of variability When we compare the individuals of the same variety or sub-variety of our older cultivated plants and animals, one of the first points which strikes us is that they generally differ more from each other than do the individuals of any one species or variety in a state of nature. And if we reflect on the vast diversity of the plants and animals which have been cultivated and which have varied during all ages under the most different climates and treatment, we are driven to conclude that this great variability is due to our domestic productions having been raised under conditions of life not so uniform as and somewhat different from those to which the parent species had been exposed under nature. There is also some probability in the view propounded by Andrew Knight that this variability may be partially connected with excess of food. It seems clear that organic beings must be exposed during several generations to new conditions to cause any great amount of variation and that when the organization has once begun to vary, it generally continues varying for many generations. No case is on record of a variable organism ceasing to vary under cultivation. Our oldest cultivated plants, such as wheat, still yield new varieties. Our oldest domesticated animals are still capable of rapid improvement or modification. As far as I am able to judge, after long attending to the subject, the conditions of life appear to act in two ways directly on the whole organization or on certain parts alone and indirectly by affecting the reproductive system. With respect to the direct action, we must bear in mind that in every case, as Professor Weisman has lately insisted and as I have incidentally shown in my work on variation under domestication, there are two factors, namely the nature of the organism and the nature of the conditions. The former seems to be much the more important, for nearly similar variations sometimes arise under, as far as we can judge, dissimilar conditions. And on the other hand, dissimilar variations arise under conditions which appear to be nearly uniform. The effects on the offspring are either definite or indefinite. They may be considered as definite when all or nearly all the offspring of individuals exposed to certain conditions during several generations are modified in the same manner. It is extremely difficult to come to any conclusion in regard to the extent of the changes which have been thus definitely induced. There can, however, be little doubt about many slight changes such as size from the amount of food, color from the nature of the food, thickness of the skin and hair from climate, etc. Each of the endless variations which we see in the plumage of our fowls must have had some efficient cause and if the same cause were to act uniformly during a long series of generations on many individuals, all probably would be modified in the same manner. Such facts as the complex and extraordinary outgrowths which variably follow from the insertion of a minute drop of poison by a gall producing insect shows us what singular modifications might result in the case of plants from a chemical change in the nature of the sap. Indefinite variability is a much more common result of change conditions than definite variability and has probably played a more important part in the formation of our domestic races. We see indefinite variability in the endless slight peculiarities which distinguish the individuals of the same species and which cannot be accounted for by inheritance from either parent or from some more remote ancestor. Even strongly marked differences occasionally appear in the young of the same litter and in seedlings from the same seed capsule. At long intervals of time, out of millions of individuals reared in the same country and fed on nearly the same food, deviations of structure so strongly pronounced as to deserve to be called monstrosities arise but monstrosities cannot be separated by any distinct line from slighter variations. All such changes of structure, whether extremely slight or strongly marked which appear among many individuals living together may be considered as the indefinite effects of the conditions of life on each individual organism in nearly the same manner as the chill effects different men in an indefinite manner according to their state of body or constitution causing coughs or colds, rheumatism or inflammation of various organs. With respect to what I have called the indirect action of changed conditions namely through the reproductive system of being affected we may infer that variability is thus induced partly from the fact of this system being extremely sensitive to any change in the conditions and partly from the similarity, as Cole Reuter and others have remarked between the variability which follows from the crossing of distinct species and that which may be observed with plants and animals when reared under new or unnatural conditions. Many facts clearly show how eminently susceptible the reproductive system is to very slight changes in the surrounding conditions. Nothing is more easy than to tame an animal and few things more difficult than to get it to breed freely under confinement even when the male and female unite. How many animals there are which will not breed though kept in an almost free state in their native country? This is generally but erroneously attributed to vitiated instincts. Many cultivated plants display the utmost rigor and yet rarely or never seed. In some few cases it has been discovered that a very trifling change such as a little more or less water at some particular period of growth will determine whether or not a plant will produce seeds. I cannot here give the details which I have collected and elsewhere published on this curious subject but to show how singular the laws are which determine the reproduction of animals under confinement I may mention that carnivorous animals even from the tropics breed in this country pretty freely under confinement with the exception of the plantagrades or bear family which seldom produce young whereas carnivorous birds with the rarest exception hardly ever lay fertile eggs. Many exotic plants have pollen utterly worthless in the same condition as in the most sterile hybrids. When on the one hand we see domesticated animals and plants though often weakened sickly breeding freely under confinement and when on the other hand we see individuals though taken young from a state of nature perfectly tamed long lived and healthy of which I could give numerous instances yet having their reproductive system so seriously affected by unperceived causes as to fail to act we need not be surprised at this system when it does act under confinement acting irregularly and producing offspring somewhat unlike their parents I may add that as some organisms breed freely under the most unnatural conditions for instance rabbits and ferrets kept in hutches showing that their reproductive organs are not easily affected so will some animals and plants withstand domestication or cultivation and vary very slightly perhaps hardly more than in a state of nature some naturalists have maintained that all variations are connected with the act of sexual reproduction but this is certainly an error for I have given in another work a long list of sporting plants as they are called by gardeners that is of plants which have suddenly produced a single bud with a new and sometimes widely different character from that of the other buds on the same plant these bud variations as they may be named can be propagated by grafts, offsets, etc and sometimes by seed they occur rarely under nature but are far from rare under a culture as a single bud out of many thousands produced year after year on the same tree under uniform conditions has been known suddenly to assume a new character and as buds on distinct trees growing under different conditions have sometimes yielded nearly the same variety for instance buds on peach trees producing nectarines and buds on common roses producing moss roses we clearly see that the nature of the conditions is of subordinate importance in comparison with the nature of the organism and determining each particular form of variation perhaps of not more importance than the nature of the spark by which a mass of combustible matter is ignited has in determining the nature of the flames effects of habit and of the use or disuse of parts correlated variation inheritance changed habits produce an inherited effect as in the period of the flowering of plants when transported from one climate to another with animals the increased use or disuse of parts has had a more marked influence thus I find in the domestic duck that the bones of the wing weigh less and the bones of the leg more in proportion to the whole skeleton then do the same bones in the wild duck and this change may be safely attributed to the domestic duck flying much less and walking more than its wild parents the great and inherited development of the udders and cows and goats in countries where they are habitually milked in comparison with these organs in other countries is probably another instance of the effects of use not one of our domestic animals can be named which has not in some country drooping ears and the view which has been suggested that the drooping is due to disuse of the muscles of the ear from the animals being seldom much alarmed seems probable many laws regulate variation some few of which can be dimly seen and will hereafter be briefly discussed I will here only allude to what may be called correlated variation important changes in the embryo or larva will probably entail changes in the mature animal in monstrosities the correlations between quite distinct parts are very curious and many instances are given in Isidore Geoffrey St. Hilaire's great work on this subject breeders believe that long limbs are almost always accompanied by an elongated head some instances of correlation are quite whimsical thus cats which are entirely white and have blue eyes are generally deaf but it has lately been stated by Mr. Tate that this is confined to the males color and constitutional peculiarities go together of which many remarkable cases could be given among animals and plants from facts collected by Hugh Singer it appears that white sheep and pigs are injured by certain plants while dark colored individuals escape Professor Wyman has recently communicated to me a good illustration of this fact on asking some farmers in Virginia how it was that all their pigs were black they informed him that the pigs black nantis which colored their bones pink and which caused the hoofs of all but the black varieties to drop off and one of the crackers i.e. Virginia Squatters added we select the black members of a litter for raising as they alone have a good chance of living hairless dogs have imperfect teeth long-haired and coarse-haired animals are apt to have as is asserted long or many horns pigeons with feathered feet have skin between their outer toes pigeons with short beaks have small feet and those with long beaks large feet hence if man goes on selecting and thus augmenting any peculiarity you will almost certainly modify intentionally other parts of the structure owing to the mysterious laws of correlation the results of the various unknown or but dimly understood laws of variation are infinitely complex and diversified it is well worthwhile carefully to study the several treaties on some of our old cultivated plants as on the hyacinth, potato even the dahlia, etc. and it is really surprising to note the endless points of structure and constitution in which the varieties and sub-varieties differ slightly from each other the whole organization seems to have become plastic and departs in a slight degree from that of the parental type any variation which is not inherited is unimportant for us but the number and diversity of inheritable deviations of structure both those of slight and those of considerable physiological importance are endless Dr. Prosper Lucas's treaties and two large volumes is the fullest and the best on this subject no breeder doubts how strong is the tendency to inheritance that like produces like is his fundamental belief doubts have been thrown on this principle only by theoretical writers when any deviation of structure often appears and we see it in the father and child we cannot tell whether it may not be due to the same cause having acted on both but when among individuals apparently exposed to the same conditions any very rare deviation due to some extraordinary combination of circumstances appears in the parent say once among several million individuals and it reappears in the child the mere doctrine of chances almost compels us to attribute its reappearance to inheritance everyone must have heard of cases of albinism prickly skin hairy bodies etc. appearing in several members of the same family if strange and rare deviations of structure are truly inherited less strange and commoner deviations may be freely admitted to be inheritable perhaps the correct way of viewing the whole subject would be to look at the inheritance of every character whatever as the rule and non inheritance as the anomaly the laws governing inheritance are for the most part unknown no one can say why the same peculiarity in different individuals of the same species or in different species is sometimes inherited and sometimes not so why the child often reverts in certain characteristics to its grandfather or grandmother or more remote ancestor why a peculiarity is often transmitted from one sex to both sexes or to one sex alone more commonly but not exclusively to the like sex it is a fact of some importance to us that peculiarities appearing in the males of our domestic breeds are often transmitted either exclusively or in a much greater degree to the males alone a much more important rule which I think may be trusted is that at whatever period of life peculiarity first appears it tends to reappear in the offspring at a corresponding age though sometimes earlier in many cases this could not be otherwise thus the inherited peculiarities in the horns of cattle could appear only in the offspring when nearly mature peculiarities in the silkworm are known to appear at the corresponding caterpillar or cocoon stage but hereditary diseases and some other facts make me believe that the rule has a wider extension and that when there is no apparent reason why a peculiarity should appear at any particular age yet that it does tend to appear in the offspring at the same period at which it first appeared in the parent I believe this rule to be of the highest importance in explaining the laws of embryology these remarks are of course confined to the first appearance of the peculiarity and not to the primary cause which may have acted on the ovules or on the male element in nearly the same manner as the increased length of the horns in the offspring from a short horned cow by a long horned bull though appearing late in life is clearly due to the male element having alluded to the subject of reversion I may here refer to a statement often made by naturalists namely that our domestic varieties when run wild gradually but invariably revert in character to their aboriginal stocks hence it has been argued that no deductions can be drawn from domestic races to species in a state of nature I have in vain endeavored to discover on what decisive facts the above statement has so often and so boldly been made there would be great difficulty in proving its truth we may safely conclude that very many of the most strongly marked domestic varieties could not possibly live in a wild state in many cases we do not know what the aboriginal stock was and so could not tell whether or not nearly perfect reversion has ensued it would be necessary in order to prevent the effects of intercrossing that only a single variety should be turned loose in its new home nevertheless as our varieties certainly do occasionally revert in some of their characteristics to ancestral forms it seems to me not improbable that if we could succeed in naturalizing or were to cultivate during many generations the several races for instance of the cabbage in very poor soil in which case however some effect would have to be attributed to the definite action of the poor soil that they would to a large extent or even wholly revert to the wild aboriginal stock whether or not the experiment would succeed is not of great importance for our line of argument for by the experiment itself the conditions of life are changed if it could be shown that our domestic varieties manifested a strong tendency to reversion that is to lose their acquired characters while kept under the same conditions and while kept in a considerable body so that free intercrossing might check by blending together any slight deviations in their structure in such case I grant that we could deduce nothing from domestic varieties in regard to species but there is not a shadow of evidence in favor of this view to a search that we could not breed our cart and race horses long and short horn cattle and poultry of various breeds and escalant vegetables for an unlimited number of generations would be opposed to all experience character of domestic varieties difficulty of distinguishing between varieties and species origin of domestic varieties from one or more species when we look to the hereditary varieties or races of our domestic animals and plants and compare them with closely allied species we generally perceive in each domestic race as already remarked this uniformity of character than in true species domestic races often have a somewhat monstrous character by which I mean that although differing from each other and from other species of the same genus in several trifling respects they often differ in an extreme degree in some one part both when compared one with another and more especially when compared with the species under nature to which they are nearest allied with these exceptions and with that of the perfect fertility of varieties when crossed a subject hereafter to be discussed domestic varieties of the same species differ from each other in the same manner as do the closely allied species of the same genus in a state of nature but the differences in most cases are less in degree this must be admitted as true for the domestic races of many animals and plants have been ranked by some competent judges as the descendants of originally distinct species and by other competent judges as mere varieties if any well-marked distinction existed between a domestic race and a species this source of doubt will not so perpetually recur it has often been stated that domestic races do not differ from each other in characters of generic value it can be shown that this statement is not correct but naturalists differ much in determining what characters are of generic value all such valuations being at present empirical when it is explained how genera originate under nature it will be seen that we have no right to expect often to find a generic amount of difference in our domesticated races in attempting to estimate the amount of structural difference between allied domestic races we are soon involved in doubt from not knowing whether they are descended from one or several parent species this point if it could be cleared up would be interesting for instance it could be shown that the greyhound bloodhound, terrier, spaniel and bulldog which we all know propagate their kind truly were the offspring of any single species then such facts would have great weight in making us doubt about the immutability of the many closely allied natural species for instance of the many foxes inhabiting the different quarters of the world I do not believe as we shall presently see that the whole amount of difference between the several breeds of the dog has been produced under domestication I believe that a small part of the difference is due to their being descended from distinct species in the case of strongly marked races of some other domesticated species there is presumptive or even strong evidence that all are descended from a single wild stock it has often been assumed that man has chosen for domestication animals and plants having an extraordinary inherent tendency to vary and likewise to withstand diverse climates I do not dispute that these capacities have added largely to the value of most of our domesticated productions but how could a savage possibly know when he first tamed an animal whether it would vary in succeeding generations and whether it would endure other climates has the little variability of the ass and the goose or the small power of endurance of warmth by the reindeer or of cold by the common camel prevented their domestication I cannot doubt that if other animals and plants equal a number to our domesticated productions and belonging to equally diverse classes and countries were taken from a state of nature and could be made to breed for an equal number of generations under domestication they would on average vary as largely as the parent species of our existing domesticated productions have varied in the case of most of our anciently domesticated animals and plants it is not possible to come to any definite conclusion whether they are descended from one or several wild species the argument mainly relied on by those who believe in the multiple origin of our domestic animals is that we find in the most ancient times on the monuments of Egypt and in the lake habitations of Switzerland much diversity in the breeds and that some of these ancient breeds closely resemble or are even identical with those still existing but this only throws far backward the history of civilization and shows that animals were domesticated at a much earlier period than has hitherto been supposed the lake inhabitants of Switzerland cultivated several kinds of wheat and barley the pea, the poppy for oil and flax and they possessed several domesticated animals they also carried on commerce with other nations all this clearly shows as here has remarked that they had at this early age progressed considerably in civilization and this again implies a long continued previous period of less advanced civilization during which the domesticated animals kept by different tribes in different districts might have varied and given rise to distinct races since the discovery of flint tools and the superficial formations of many parts of the world all geologists believe that barbarian men existed at an enormously remote period and we know that at the present day there is hardly a tribe so barbarous as not to have domesticated at least the dog the origin of most of our domestic animals will probably forever remain vague but I may here state that looking to the domestic dogs of the whole world I have after a laborious collection of all known facts come to the conclusion that several wild species of canady have been tamed and that their blood in some cases mingled together flows in the veins of our domestic breeds in regard to sheep and goats I can form no decided opinion from facts communicated to me by Mr. Blythe in the habits, voice, constitution and structure of the humped Indian cattle it is almost certain that they are descended from a different aboriginal stock from our European cattle and some competent judges believe that these latter have had two or three wild progenitors whether or not these deserve to be called species this conclusion as well as that of the specific distinction between the humped and common cattle may indeed be looked upon as established by the admirable researches of Professor Rüttemeyer with respect to horses from reasons which I cannot give here I am doubtfully inclined to believe an opposition to several authors that all the races belong to the same species having kept nearly all the English breeds of the fowl alive having bred and crossed them and examined their skeletons it appears to me almost certain that all are the descendants of the wild Indian fowl Gala Spankiva and this is the conclusion of Mr. Blythe and of others who have studied this bird in India in regard to ducks and rabbits some breeds of which differ much from each other the evidence is clear that they are all descended from the common duck and wild rabbit the doctrine of the origin of our several domestic races from several aboriginal stocks has been carried to an absurd extreme by some authors they believe that every race which breeds true let the distinctive characters be ever so slight has had its wild prototype at this rate there must have existed at least a score of species of wild cattle as many sheep and several goats in Europe alone and several even within Great Britain one author believes that there formerly existed eleven wild species of sheep peculiar to Great Britain when we bear in mind that Britain has now not one peculiar mammal and France but few distinct from those of Germany and so with Hungary, Spain, etc. but that each of these kingdoms possesses peculiar breeds of cattle, sheep, etc. we must admit that many domestic breeds must have originated in Europe for once otherwise could they have been derived so it is in India even in the case of the breeds of the domestic dog throughout the world which I admit are descended from several wild species it cannot be doubted that there has been an immense amount of inherited variation for who will believe that animals closely resembling the Italian greyhound, the bloodhound the bull dog, pug dog or Blenheim spaniel, etc. so unlike all wild canady ever existed in a state of nature it has often been loosely said that all our races of dogs have been produced by the crossing of a few aboriginal species but by crossing we can only get forms in some degree intermediate between their parents and if we account for our several domestic races by this process we must admit the former existence of the most extreme forms as the Italian greyhound bloodhound, bulldog, etc. in the wild state moreover the possibility of making distinct races by crossing has been greatly exaggerated so many cases are on record showing that a race may be modified by occasional crosses if aided by the careful selection of the individuals which present the desired character but to obtain a race intermediate between two quite distinct races would be very difficult Sir J. Seabright expressly experimented with this object and failed the offspring from the first cross between them is tolerably and sometimes as I have found with pigeons quite uniform in character and everything seems simple enough but when these mongrels are crossed one with another for several generations hardly two of them are alike and then the difficulty of the task becomes manifest End of Chapter 1 Section A This is a LibriVox recording All LibriVox recordings are in the public domain For more information or to volunteer please visit LibriVox.org Recorded by Annie Coleman in St. Louis, Missouri in April 2006 The Origin of Species by Means of Natural Selection or the Preservation of Favored Races and the Struggle for Life Sixth London Edition by Charles Darwin Chapter 1 Part B Breeds of the Domestic Pigeon Their Differences and Origin Believing that it is always best to study some special group I have, after deliberation, taken up domestic pigeons I have kept every breed which I could purchase or obtain and have been most kindly favored with skins from several quarters of the world more especially by the Honorable W. Eliot from India and by the Honorable C. Murray from Persia Many treaties in different languages have been published on pigeons and some of them are very important as being of considerable antiquity I have associated with several eminent fanciers and have been permitted to join two of the London pigeon clubs The diversity of the breeds is something astonishing Compare the English carrier and the short-faced tumbler and see the wonderful difference in their beaks entailing corresponding differences in their skulls The carrier, more especially the male bird is also remarkable from the wonderful development of the carunculated skin about the head and this is accompanied by greatly elongated eyelids very large external orifices to the nostrils and a wide gape of mouth The short-faced tumbler has a beak in outline almost like that of a finch and the common tumbler has the singular inherited habit of flying at a great height in a compact flock and tumbling in the air head over heels The runt is a bird of great size with long, massive beak and large feet Some of the sub-breeds of runts have very long necks others have very long wings and tails others singularly short tails The barb is allied to the carrier but instead of a long beak has a very short and broad one The powder has a much elongated body, wings and legs and its enormously developed crop which it glories in inflating may well excite astonishment and even laughter The turbot has a short and conical beak with a line of reversed feathers down the breast and it has the habit of continually expanding slightly the upper part of the esophagus The Jacobin has the feathers so much reversed along the back of the neck that they form a hood and it has proportionally to its size elongated wings and tail feathers The trumpeter and laffer, as their names express utter a very different coup from the other breeds The fantail has 30 or even 40 tail feathers instead of 12 or 14 the normal number in all the members of the Great Pigeon Family These feathers are kept expanded and are carried so erect that in good birds the head and tail touch the oil gland is quite aborted Several other less distinct breeds might be specified In the skeletons of the several breeds the development of the bones of the face in length and breadth and curvature differs enormously The shape as well as the breadth and length of the ramus of the lower jaw varies in a highly remarkable manner The caudal and sacral vertebrae vary in number, as does the number of the ribs together with their relative breadth and the presence of processes The size and shapes of the apertures in the sternum are highly variable So is the degree of divergence and relative size of the two arms of the fercula The proportional width of the gape of mouth the proportional length of the eyelids of the orifice of the nostrils of the tongue not always in strict correlation with the length of beak The size of the crop and of the upper part of the esophagus the development and abortion of the oil gland the number of the primary wing and caudal feathers the relative length of the wing and tail to each other and to the body the relative length of the leg and foot the number of scutelli on the toes the development of skin between the toes are all points of structure which are variable The period at which the perfect plumage is acquired varies as does the state of the down with which the nestling birds are clothed when hatched The shape and size of the eggs vary the manner of flight and some breeds the voice and disposition differ remarkably Lastly, in certain breeds the males and females have come to differ in a slight degree from each other All together at least a score of pigeons might be chosen which, if shown to an ornithologist and he were told that they were wild birds would certainly be ranked by him as well-defined species Moreover, I do not believe that any ornithologist would in this case place the English carrier the short-faced tumbler the runt the barb the pouter and fantail in the same genus more especially as in each of these breeds several truly inherited sub-breeds or species as he would call them could be shown him Great as are the differences between the breeds of the pigeon I am fully convinced that the common opinion of naturalists is correct namely that all are descended from the rock pigeon Columba Livia including under this term several geographical races or sub-species which differ from each other in the most trifling respects As several of the reasons which have led me to this belief are in some degree applicable in other cases I will here briefly give them If the several breeds are not varieties and have not proceeded from the rock pigeon they must have descended from at least 7 or 8 aboriginal stocks for it is impossible to make the present domestic breeds by the crossing of any lesser number How, for instance, could a pouter be produced by crossing two breeds unless one of the parent stocks possessed the characteristic enormous crop The supposed aboriginal stocks must all have been rock pigeons that is, they did not breed or willingly perch on trees But besides Columba Livia with its geographical sub-species only two or three other species of rock pigeons are known and these have not any of the characters of the domestic breeds Hence, the supposed aboriginal stocks must either still exist in the countries where they were originally domesticated and yet be unknown to ornithologists and this, considering their size, habits and remarkable characters seems improbable or they must have become extinct in the wild state But birds breeding on precipices and good fliers are unlikely to be exterminated and the common rock pigeon which has the same habits with the domestic breeds has not been exterminated even on several of the smaller British islets or on the shore of the Mediterranean Hence, the supposed extermination of so many species having similar habits with the rock pigeon seems a very rash assumption Moreover, the several above-named domesticated breeds have been transported to all parts of the world and therefore some of them must have been carried back again into their native country but not one has become wild or feral though the dove-coat pigeon which is the rock pigeon in a very slightly altered state has become feral in several places Again, all of recent experience shows that it is difficult to get wild animals to breed freely under domestication yet on the hypothesis of the multiple origin of our pigeons it must be assumed that at least seven or eight species were so thoroughly domesticated in ancient times by half-civilized man as to be quite prolific under confinement An argument of great weight and applicable in several other cases is that the above-specified breeds though agreeing generally with a wild rock pigeon in constitution habits, voice, coloring and in most parts of their structure yet are certainly highly abnormal in other parts we may look in vain through the whole family of columbidae for a beak like that of the English carrier or that of the short-faced tumbler or barb for reversed feathers like those of the Jacobin for a crop like that of the pouter for tail feathers like those of the fantail hence it must be assumed not only that half-civilized man succeeded in thoroughly domesticating several species but that he intentionally or by chance picked out extraordinarily abnormal species and further that these very species have since all become extinct or unknown so many strange contingencies are improbable in the highest degree some facts in regard to the coloring of pigeons well-deserved consideration the rock pigeon is of a slaty blue with white loins but the Indian subspecies columba intermedia of Strickland has this part bluish the tail has a terminal dark part with the outer feathers externally edged at the base with white the wings have two black bars some semi-domestic breeds and some truly wild breeds have besides the two black bars the wings checkered with black these several marks do not occur together in any other species of the whole family now in every one of the domestic breeds taking thoroughly well-bred birds all the above marks even to the white edging of the outer tail feathers sometimes concur perfectly developed moreover when birds belonging to two or more distinct breeds are crossed none of which are blue or have any of the above specified marks the mongrel offspring are very apt suddenly to acquire these characters to give one instance out of several which I have observed I crossed some white fan tails which breed very true with some black barbs and it so happens that blue varieties of barbs are so rare that I never heard of an instance in England and the mongrels were black, brown and mottled I also crossed a barb with a spot which is a white bird with a red tail and red spot on the forehead in which notoriously breeds very true the mongrels were dusky and mottled I then crossed one of the mongrel barb fan tails with a mongrel barb spot and they produced a bird of as beautiful a blue color with the white loins, double black wing bar and barred and white edged tail feathers as any wild rock pigeon we can understand these facts on the well-known principle of reversion to ancestral characters if all the domestic breeds are descended from the rock pigeon but if we deny this we must make one of the two following highly improbable suppositions either first that all of the several imagined aboriginal stocks were colored and marked like the rock pigeon although no other existing species is thus colored and marked so that in each separate breed there might be a tendency to revert to the very same colors and markings or secondly that each breed, even the purest has within a dozen or at most within a score of generations been crossed by the rock pigeon I say within a dozen or twenty generations for no instance is known of crossed descendants reverting to an ancestor of foreign blood removed by a greater number of generations in a breed which has been crossed only once the tendency to revert to any character derived from such a cross will naturally become less and less as in each succeeding generation there will be less of the foreign blood but when there has been no cross and there is a tendency in the breed to revert to a character which was lost during some former generation this tendency for all that we can see to the contrary may be transmitted undiminished for an indefinite number of generations these two distinct cases of reversion are often compounded together by those who have written on inheritance lastly the hybrids or mongrels from between all the breeds of the pigeon are perfectly fertile as I can state from my own observations purposely made on the most distinct breeds now hardly any cases have been ascertained with certainty of hybrids from two quite distinct species of animals being perfectly fertile some others believe that long continued domestication eliminates this strong tendency to sterility in species from the history of the dog and of some other domestic animals this conclusion is probably quite correct if applied to species closely related to each other but to extend it so far as to suppose that species aboriginally as distinct as carriers tumblers, powders and fantails now are should yield offspring perfectly fertile interse seems to me rash in the extreme from these several reasons namely the improbability of man having formerly made seven or eight supposed species of pigeons to breed freely under domestication these supposed species being quite unknown in a wild state and they're not having become anywhere feral these species presenting certain very abnormal characters as compared with all other columbidae though so like the rock pigeon in most other respects the occasional reappearance of the blue color and various black marks in all the breeds both one kept pure and one crossed and lastly the mongrel offspring being perfectly fertile from these several reasons taken together we may safely conclude that all our domestic breeds are descended from the rock pigeon or columbolivia with its geographical subspecies in favor of this view I may add firstly that the wild columbolivia has been found capable of domestication in Europe and in India and that it agrees in habitats and in a great number of points of structure with all the domestic breeds secondly that although an English carrier or a short-faced tumbler differs immensely in certain characters from the rock pigeon yet that by comparing the several sub-breeds of these two races more specially those brought from distant countries we can make between them and the rock pigeon an almost perfect series so we can in some other cases but not with all the breeds thirdly those characters which are mainly distinctive of each breed are in each eminently variable for instance the waddle and length of beak the carrier the shortness of that of the tumbler and the number of tail feathers in the fan-tail from the explanation of this fact will be obvious when we treat of selection fourthly pigeons have been watched intended with the utmost care and loved by many people they have been domesticated for thousands of years in several quarters of the world the earliest known record of pigeons is in the fifth Egyptian dynasty about 3000 BC as was pointed out to me by professor Lepceus but Mr. Birch informs me that pigeons are given in a bill of fare in the previous dynasty in the time of the Romans as we hear from Pliny immense prices were given for pigeons nay they are come to this pass that they can reckon up their pedigree and race pigeons were much valued by Agpur Khan in India about the year 1600 nevertheless than 20,000 pigeons were taken with the court the monarchs of Iran and Tehran sent him some very rare birds and continues the courtly historian his majesty by crossing the breeds which method was never practiced before has improved them astonishingly about this same period the Dutch were as eager about pigeons as were the old Romans the paramount importance of these considerations in explaining the immense amount of variation which pigeons have undergone will likewise be obvious when we treat of selection we shall then also see how it is that the several breeds so often have a somewhat monstrous character it is also a most favorable circumstance for the production of distinct breeds that male and female pigeons can be easily mated for life and thus different breeds can be kept together in the same aviary I have discussed the probable origin of domestic pigeons at some yet quite insufficient length because when I first kept pigeons and watched the several kinds well knowing how truly they breed I felt fully as much difficulty in believing that since they had been domesticated they had all proceeded from a common parent as any naturalist could in coming to a similar conclusion in regard to the many species of finches or other groups of birds in nature one circumstance has struck me much namely that nearly all the breeders of the various domestic animals and the cultivators of plants with whom I have conversed or whose treaties I have read are firmly convinced that the several breeds to which each has attended are descended from so many aboriginally distinct species ask, as I have asked a celebrated razor of Hareford cattle whether his cattle might not have descended from longhorns or both from a common parent stock and he will laugh you to scorn I have never met a pigeon or poultry or duck or rabbit fancier who is not fully convinced that each main breed was descended from a distinct species Van Montz in his treaties on pairs and apples shows how utterly he disbelieves that the several sorts, for instance of Ribston Pippin or Codlin Apple could ever have proceeded from the seeds of the same tree innumerable other examples could be given the explanation I think is simple from long continued study they are strongly impressed with the differences between the several races and though they well know that each race varies slightly for they win their prizes by selecting such slight differences yet they ignore all general arguments and refuse to sum up in their minds slight differences accumulated during many successive generations may not those naturalists who, knowing far less of the laws of inheritance than does the breeder and knowing no more than he does of the intermediate links in the long lines of descent yet admit that many of our domestic races are descended from the same parents may they not learn a lesson of caution when they deride the idea of species in a state of nature being lineal descendants of other species principles of selection anciently followed and their effects let us now briefly consider the steps by which domestic races have been produced either from one or from several allied species some effect may be attributed to the direct and definite action of the external conditions of life and some to habit but he would be a bold man who would account by such agencies for the differences between a dre and racehorse a greyhound and bloodhound a carrier and tumbler pigeon one of the most remarkable features in our domesticated races is that we see in them adaptation not indeed to the animals or plants own good but to man's use or fancy some variations useful to him have probably arisen suddenly or by one step many botanists for instance believe that the fuller's teasel with its hooks which cannot be rivaled by any mechanical contrivance is only a variety of the wild dipsicus and this amount of change may have suddenly arisen in a seedling so it has probably been with the turnspit dog and this is known to have been the case with the anken sheep but when we compare the dre horse and racehorse the dromedary and camel the various breeds of sheep fitted either for cultivated land or mountain pasture with the wool of one breed good for one purpose and that of another breed for another purpose when we compare the many breeds of dogs each good for man in different ways when we compare the game cock so pertinacious breeds so little quarrelsome with everlasting layers which never desire to sit and with the bantam so small and elegant when we compare the host of agricultural culinary orchard and flower garden races of plants most useful to man at different seasons and for different purposes or so beautiful in his eyes we must I think look further than to mere variability we cannot suppose that all the breeds were suddenly produced as perfect and as useful as we now see them indeed in many cases we know that this has not been their history the key is man's power of accumulative selection nature gives successive variations man adds them up in certain directions useful to him in this sense he may be said to have made for himself useful breeds the great power of this principle of selection is not hypothetical it is certain that several of our eminent breeders have even within a single lifetime modified to a large extent their breeds of cattle and sheep in order fully to realize what they have done it is almost necessary to read several of the many treaties devoted to this subject and to inspect the animals breeders habitually speak of an animal's organization as something plastic which they can model almost as they please if I had space I could quote numerous passages to this effect from highly competent authorities you at who is probably better acquainted with the works of agricultural lists than any other individual and who was himself a very good judge of animals speaks of the principle of selection as that which enables the agriculturalist not only to modify the character of his flock but to change it all together it is the magicians wand by means of which he may summon into life whatever form and mold he pleases Lord Somerville speaking of what breeders have done for sheep says it would seem as if they had chalked out upon a wall a form perfect in itself and then had given its existence in Saxony the importance of the principle of selection in regard to merino sheep is so fully recognized that men follow it as a trade the sheep are placed on a table and are studied like a picture by a connoisseur this is done three times at intervals of months and the sheep are each time marked and classed so that the very best may ultimately be selected for breeding what English breeders have actually affected is proved by the enormous prices given for animals with a good pedigree and these have been exported to almost every quarter of the world the improvement is by no means generally due to crossing different breeds all the best breeders are strongly opposed to this practice except sometimes among closely allied sub-breeds and when a cross has been made the closest selection is far more indispensable even than in ordinary cases if selection consisted merely in separating some very distinct variety and breeding from it the principle would be so obvious as hardly to be worth notice the importance consists in the great effect produced by the accumulation in one direction during successive generations of differences absolutely inappreciable by an uneducated eye differences which I for one have vainly attempted to appreciate not one man in a thousand has accuracy of eye and judgment sufficient to become an eminent breeder if gifted with these qualities and he studies his subject for years and devotes his lifetime to it with indomitable perseverance he will succeed and may make great improvements if he wants any of these qualities he will assuredly fail few would readily believe in the natural capacity and years of practice requisite to become even a skillful pigeon fancier the same principles are followed by horticulturalists but the variations are here often more abrupt no one supposes that our choice productions have been produced by a single variation from the aboriginal stock we have proofs that this is not so in several cases in which exact records have been kept thus to give a very trifling instance the steadily increasing size of the common gooseberry may be quoted to be an astonishing improvement in many florists' flowers when the flowers of the present day are compared with drawings made only 20 or 30 years ago when a race of plants is once pretty well established the seed raisers do not pick out the best plants but merely go over their seed beds and pull up the rogues as they call the plants that deviate from the proper standard with animals in fact likewise followed for hardly anyone is so careless as to breed from his worst animals in regard to plants there is another means of observing the accumulated effects of selection namely by comparing the diversity of flowers in the different varieties of the same species in the flower garden the diversity of leaves pods or tubers or whatever part is valued in the kitchen garden in comparison with the flowers of the same varieties and the diversity of fruit of the same species in the orchard in comparison with the leaves and flowers of the same set of varieties see how different the leaves of the cabbage are and how extremely alike the flowers how unlike the flowers of the heartsees are and how alike the leaves how much the fruit berries differ in size color shape and hairiness and yet the flowers present very slight differences it is not that the varieties which differ largely in some one point do not differ at all in other points this is hardly ever I speak after careful observation perhaps never the case the law of correlated variation the importance of which should never be overlooked will ensure some differences but as a general rule it cannot be doubted that the continued selection of slight variations either in the leaves the flowers or the fruit will produce races differing from each other chiefly in these characters it may be objected that the principle of selection has been reduced to methodical practice for scarcely more than three quarters of a century it has certainly been more attended to of late years and many treaties have been published on the subject and the result has been in a corresponding degree rapid and important but it is very far from true that the principle is a modern discovery I could give several references to works of high antiquity in which the full importance of the principle is acknowledged in rude and barbarous periods of English history choice animals were often imported and laws were passed to prevent their exportation the destruction of horses under a certain size was ordered and this may be compared to the roguing of plants by nurserymen the principle of selection I find distinctly given in an ancient Chinese encyclopedia explicit rules are laid down by some of the Roman classical writers from passages in Genesis it is clear that the color of domestic animals was at that early period attended to savages now sometimes cross their dogs with wild canine animals to improve the breed and they formerly did so as is attested by passages in Pliny the savages in South Africa distinguish their draft cattle by color as do some of the Eskimo their teams of dogs Livingstone states that good domestic breeds are highly valued by the Negroes in the interior of Africa who have not associated with Europeans some of these facts do not show actual selection but they show that the breeding of domestic animals was carefully attended to in ancient times and is now attended to the lowest savages it would indeed have been a strange fact had attention not been paid to breeding for the inheritance of good and bad qualities is so obvious unconscious selection at the present time eminent breeders try by methodical selection with a distinct object in view to make a new strain or sub-breed but for our purpose a form of selection which may be called unconscious and which results from everyone trying to possess and breed from the best individual animals is more important thus a man who intends keeping pointers naturally tries to get as good dogs as he can and afterwards breeds from his own best dogs but he has no wish or expectation of permanently altering the breed nevertheless we may infer that this process continued during centuries would improve and modify any breed in the same way as Bakewell Collins etc by this very same process only carried on more methodically did greatly modify even during their lifetimes the forms and qualities of their cattle slow and insensible changes of this kind could never be recognized unless actual measurements or careful drawings of the breeds in question have been made long ago which may serve for comparison in some cases however unchanged or but little changed individuals of the same breed exist in less civilized districts where the breed has been less improved there is reason to believe that the breed of the Spaniel has been unconsciously modified to a large extent since the time of that monarch some highly competent authorities are convinced that the setter is directly derived from the Spaniel and has probably been slowly altered from it it is known that the English pointer has been greatly changed within the last century and in this case the change has it is believed to have been affected by crosses with the foxhound but what concerns us is that the change has been affected unconsciously and gradually and yet so effectually that though the old Spanish pointer certainly came from Spain Mr. Baro has not seen as I am informed by him any native dog in Spain like our pointer by a similar process of selection English resources have come to surpass in fleetness and size the parent Arabs so that the latter by the regulations for the Goodwood races are favored in the weights which they carry Lord Spencer and others have shown how the cattle of England have increased in weight and in early maturity compared with the stock formerly kept in this country by comparing the accounts of the old treaties of the former and present state of carrier and tumbler pigeons and Britain, India and Persia we can trace the stages through which they have insensibly passed and come to differ so greatly from the rock pigeon Uot gives an excellent illustration of the effects of a course of selection which may be considered as unconscious in so far that the breeders could never have expected or even wished to produce the results which ensued namely the production of the distinct strains the two flocks of Lester sheep kept by Mr. Buckley and Mr. Burgess as Mr. Uod remarks have been purely bred from the original stock of Mr. Bakewell for upwards of 50 years there is not a suspicion existing in the mind of anyone at all acquainted with the subject the owner of either of them has deviated in any one instance from the pure blood of Mr. Bakewell's flock and yet the difference between the sheep possessed by these two gentlemen is so great that they have the appearance of being quite different varieties if there exist savages so barbarous as never to think of the inherited character of the offspring of their domestic animals yet any one animal really useful to them for any special purpose would be carefully preserved during famines and other accidents to which savages are so liable and such choice animals would thus generally leave more offspring than the inferior ones so that in this case there would be a kind of an unconscious selection going on we see the value set on animals even by the barbarians of Tierra del Fuego by their killing and devouring of old women in times of earth as of less value than their dogs in plants the same gradual process of improvement through the occasional preservation of the best individuals whether or not sufficiently distinct to be ranked at their first appearance as distinct varieties and whether or not two or more species or races have become blended together by crossing may plainly be recognized in the increased size and beauty which we now see in the varieties of the heart sees, rose pelagonium, dahlia and other plants and when compared with the older varieties or with their parent stocks no one would ever expect to get a first rate heart sees or dahlia from the seed of a wild plant no one would expect to raise a first rate melting pair from the seed plant pair though he might succeed from a poor seedling growing wild if it had come from a garden stock the pair though cultivated in classical times appears from Pliny's description to have been a fruit of very inferior quality I have seen great surprise expressed in horticultural works at the wonderful skill of gardeners in having produced such splendid results from such poor materials but the art has been simple and as far as the final result is concerned has been followed almost unconsciously it has consisted in always cultivating the best known variety sowing its seeds and when a slightly better variety chance to appear selecting it and so onwards but the gardeners of the classical period who cultivated the best pairs which they could procure never thought what splendid fruit we should eat though we owe our excellent fruit in some small degree to there having naturally chosen and preserved the best varieties they could anywhere find a large amount of change thus slowly and unconsciously accumulated explains as I believe the well known fact that in a number of cases we cannot recognize and therefore do not know the wild parent stocks of the plants which have been longest cultivated in our flower and kitchen gardens if it has taken centuries or thousands of years to improve or modify most of our plants up to their present standard of usefulness to man we can understand how it is that neither Australia the Cape of Good Hope nor any other region inhabited by quite uncivilized man has afforded us a single plant worth culture it is not that these countries so rich in species do not by a strange chance possess the aboriginal stocks of any useful plants but that the native plants have not been improved by continued selection up to a standard of perfection comparable with that acquired by the plants in countries anciently civilized in regard to the domestic animals kept by uncivilized man it should not be overlooked that they almost always have to struggle for their own food at least during certain seasons and in two countries very differently circumstance individuals of the same species having slightly different constitutions or structure would often succeed better in the one country than in the other and thus by a process of natural selection as will hereafter be more fully explained two sub-breeds might be formed this perhaps partly explains why the varieties kept by savages as has been remarked by some authors have more of the character of true species than the varieties kept in civilized countries on the view here given of the important part which selection by man has played it becomes at once obvious how it is that our domestic races show adaptation in their structure or in their habits to man's wants or fancies we can I think further understand the frequently abnormal character of our domestic races and likewise their differences being so great in external characters and relatively so slight in internal parts or organs man can hardly select any with much difficulty any deviation of structure accepting such as is externally visible and indeed he rarely cares for what is internal he can never act by selection accepting on variations which are first given to him in some slight degree by nature no man would ever try to make a fan tale till he saw a pigeon with a tale developed in some unusual manner or a powder till he saw a pigeon with a crop of somewhat unusual size and the more abnormal or unusual any character was when it first appeared the more likely it would be to catch his attention but to use such an expression as trying to make a fan tale is I have no doubt in most cases utterly incorrect the man who first selected a pigeon with a slightly larger tail never dreamed what the descendants of that pigeon would become through long continued partly unconscious and partly methodical selection perhaps the parent bird of all fan tales had only 14 tail feathers somewhat expanded like the present java fan tale or like individuals of other and distinct breeds and which as many as 17 counted perhaps the first powder pigeon did not inflate its crop much more than the turbid now does the upper part of its esophagus a habit which is disregarded by all fanciers as it is not one of the points of the breed nor let it be thought that some great deviation of structure would be necessary to catch the fancier's eye he perceives extremely small in nature to value any novelty however slight in one's own possession nor must the value which would formerly have been set on any slight differences in the individuals of the same species be judged of by the value which is now set on them after several breeds have fairly been established it is known that with pigeons many slight variations now occasionally appear but these are rejected as or deviations from the standard of perfection in each breed the common goose has not given rise to any marked varieties hence the Toulouse and the common breed which differ only in color that most fleeting of characters have lately been exhibited as distinct at our poultry shows these views appear to explain what has sometimes been noticed namely that we know hardly anything about the origin or history of any of our domestic breeds but in fact a breed like a dialect of a language can hardly be said to have a distinct origin a man preserves and breeds from an individual with some slight deviation of structure or takes more care than usual in matching his best animals and thus improves them and the improved animals slowly spread in the immediate neighborhood but they will as yet hardly have a distinct name and from being only slightly valued their history will have been disregarded when further improved by the same slow and gradual process they will spread more widely and will be recognized as something distinct and valuable and will then probably first receive a provincial name in semi-civilized countries with little free communication the spreading of a new sub-breed will be a slow process as soon as the points of value are once acknowledged the principle as I have called it of unconscious selection will always tend perhaps more at one period than at another as the breed rises or falls in fashion perhaps more in one district than in another according to the definition of the inhabitants slowly to add to the characteristic features of the breed whatever they may be but the chance will be infinitely small of any record having been preserved of such slow, varying and insensible changes circumstances favorable to man's power of selection I will now say a few words on the circumstances favorable or the reverse to man's power of selection a high degree of variability is obviously favorable as freely giving the materials for selection to work on not that mere individual differences are not amply sufficient with extreme care to allow of the accumulation of a large amount of modification in almost any desired direction but as variations manifestly useful or pleasing to man appear only occasionally the chance of their appearance will be much increased by a large number of individuals being kept hence number is of the highest importance for success on this principle Marshall formally remarked with respect to the sheep of part of Yorkshire as they generally belong to poor people and are mostly in small lots they never can be improved on the other hand nursery men from keeping large stocks of the same plant are generally far more successful than amateurs in raising new and valuable varieties a large number of individuals of an animal or plant can be reared only where the conditions for its propagation are favorable when the individuals are scanty all will be allowed to breed whatever their quality may be and this will effectually the plant selection but probably the most important element is that the animal or plant should be so highly valued by man that the closest attention is paid to even the slightest deviations in its qualities or structure unless such attention be paid nothing can be affected I have seen it gravely remarked that it was most fortunate that the strawberry began to vary just when gardeners began to attend to this plant no doubt the strawberry had always varied since it was cultivated but the slight varieties had been neglected as soon however as gardeners picked out individual plants with slightly larger earlier or better fruit and raised seedlings from them and again picked out the best seedlings and bred from them then with some aid by crossing species those many admirable varieties of the strawberry were raised which have appeared during the last half century with animals facility in preventing crosses is an important element in the formation of new races at least in a country which is already stocked with other races in this respect enclosure of the land plays a part wandering savages or the inhabitants of open plains rarely possess more than one breed of the same species pigeons can be mated for life and this is a great convenience to the fancier for thus many races may be improved and kept true though mingled in the same aviary in this circumstance must have largely favored the formation of new breeds pigeons I may add can be propagated in great numbers and at a very quick rate and inferior birds may be freely rejected as when killed they serve for food on the other hand cats from their nocturnal rambling habits cannot be easily matched and although so much valued by women and children we rarely see a distinct breed long kept up such breeds as we do sometimes see are almost always imported from some other country although I do not doubt that some domestic animals vary less than others yet the rarity or absence of distinct breeds of the cat, the donkey peacock, goose etc may be attributed in main part to selection not having been brought into play in cats for the difficulty in pairing them in donkeys from only a few being kept by poor people and little attention paid to their breeding for recently in certain parts of Spain and of the United States this animal has been surprisingly modified and improved by careful selection in peacocks from not being very easily reared and a large stock not kept in geese from being valuable only for two purposes food and feathers and more especially from no pleasure having been felt in the display of distinct breeds but the goose under the conditions to which it is exposed when domesticated seems to have a singularly inflexible organization though it has varied to a slight extent as I have elsewhere described some authors have maintained that the amount of variation in our domestic productions is soon reached and can never afterward be exceeded it would be somewhat rash to assert that the limit has been attained in any one case for almost all our animals and plants have been greatly improved in many ways within a recent period and this implies variation it would be equally rash to assert that characters now increased to their utmost limit could not after remaining fixed for many centuries again vary under new conditions of life no doubt as Mr. Wallace has remarked with much truth a limit will be at last reached for instance there must be a limit to the flatness of any terrestrial animal as this will be determined by the friction to be overcome the weight of the body to be carried and the power of contraction in the muscular fibers but what concerns us is that the domestic varieties of the same species differ from each other in almost every character which man has attended to and selected more than do the different species of the same genera Isidore Geoffrey Saint-Hilaire has proved this in regard to size and so it is with color and probably with the length of hair with respect to flatness which depends on many bodily characters eclipse was far fleeter and a dreahorse is comparably stronger in any two natural species belonging to the same genus so with plants the seeds of the different varieties of the bean or maize probably differ more in size than do the seeds of the distinct species in any one genus in the same two families the same remark holds good in regard to the fruit of the several varieties of the plum and still more strongly with the melon as well as in many other analogous cases to sum up on the origin of our domestic races of animals and plants changed conditions of life are of the highest importance in causing variability both by acting directly on the organization and indirectly by affecting the reproductive system it is not probable that variability is an inherent and necessary contingent under all circumstances the greater or less force of inheritance and reversion determine whether variations shall endure variability is governed by many unknown laws of which correlated growth is probably the most important something but how much we do not know may be attributed to the definite action of the conditions of life some perhaps a great effect may be attributed to the increased use or disuse of parts the final result is thus rendered infinitely complex in some cases the intercrossing of aboriginally distinct species appears to have played an important part in the origin of our breeds when several breeds have once been formed in any country their occasional intercrossing with the aid of selection has no doubt largely aided in the formation of sub-breeds but the importance of crossing has been much exaggerated both in regard to animals and to those plants which are propagated by seed with plants which are temporarily propagated by cuttings, spuds, etc the importance of crossing is immense for the cultivator may hear disregard the extreme variability both of hybrids and of mongrels and the sterility of hybrids but plants not propagated by seed are of little importance to us for their endurance is only temporary over all these causes of change the accumulative action of selection whether applied methodically and quickly or unconsciously and slowly but more efficiently seems to have been the predominant power