file:/u:/darwin/darwin_1859_01.xml 69066 962 8328 12.1% file:/u:/darwin/darwin_1860_01.xml 69331 964 8593 12.4% file:/u:/darwin/darwin_1872_01.xml 73514 950 12776 17.4% file:/u:/diff/diff-diff.xml 81999 1919 21261 25.9% darwin_1859_01 darwin_1860_01 darwin_1872_01 3284 81999 58 222 0.002707350089635239 18 266 0.003243941999292674 ar or some the breeds h v e . Knowing, as we do, that savages are very fond taming mals, it seems to me unlikely, in the case of the og-genus, which is distributed in a wild state throughout the world, that since man first appeared one single species alone should at va i i - z 886 12337 0.150453054305540311 893 7997 0.097525579580238783 11 109 0.001329284503469555 , the s me - ' ' which are first given to him in some slight degree by nature. No man would ever try to make a ' ' s ' 53 330 0.004024439322430761 1365 60738 0.740716350199392676 0.993316329111180156 0.85435544957217001 0.993316329111180156 0.855024677097553292 0.855024677097553292 0.85435544957217001 WHEN we l c o ok to mpare 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 m uch m ore from each other , than do the individuals of any one species or variety in a state of nature. Whe A n d 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, I think we are driven to conclude that this great er variability is simply 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 ha ve d been exposed under nature. There is , also, I think, some probability in the view propounded by Andrew Knight, that this variability may be partly connected with excess of food. It seems pretty clear that organic beings must be exposed during several generations to the new conditions of life to cause any app g re ci a ble t amount of variation; and that , when the organisation has once begun to vary, it generally continues to vary ing for many generations. No case is on record of a variable be organ i ng sm ceasing to be var iable y under cultivation. Our oldest cultivated plants, such as wheat, still often yield new varieties: our oldest domesticated animals are still capable of rapid improvement or modification. It As h far as I am a b l e to judg e n , dispu af te d r long at tending w to t h a e subjec t , p th e r condit io d ns of life appear to act in two ways,—directly on the whole organisation 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 Weismann 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, colour from the nature of the food, thickness of the skin and hair from climate, &c. 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 out-growths which invariably follow from the insertion of a minute drop of poison by a gall-producing insect, show us what singular modifications might result in the ca u se s of plants from a chemical change in the nature of the sap. Indefinite variability is a much more common result of changed conditions than definite variability , w and ha s probably played a more impor t eve ant pa r t in the y for ma y be, generally ac t ; ion whethe of ou r d u omestic races. We see indefinite va ri ability i n g the e ar nd l y ess or s l a igh t e pe culia ri od ties of which d istinguish th e indi v e idua l opment s of the sam e species, and which cannot be accounted for by inheritance fro m b eithe r yo, parent or from some more remote a nces t or. Even strongly-marked differences occasionally appear in the instant of conception. Geoffro y St. Hilaire's experiments sh o w that un natural treatment g of the sam e litter, and in seedlings fro m b the same seed-capsule. At long intervals of time, out of millions of individuals reared in the same count ry and fed o n nearly the same food, deviations of structure so strongly pronounced as to deserve to be ca us ll e s d monstrosities arise ; and but monstrosities cannot be separated by any clear line of distinct l i o n e from m slight er e variations. B All s u ch changes of structure, whether extremely sligh t I am or strongly inclin mark ed , to which sus ap pe ct th a t r the a mo ng st frequent c m a use ny of var i ndividu a bi ls li ving t y ogether, may be attributed to the male and female reproductive elements having been affected prior to the act of con cept s i on. Sev d er al r e asons d m a ke me believe in this; but the chief one i s the r ind e markabl finit e effect s w of t h ich e con ditions of life on each individual organism, in nearly the same manner as a chill affects different men in an inde fin it e m ann e r, accordi n g t o their state of body or c ul ons ti v tution, causing coughs or colds, rheumatism, or inflamm ation s of various organs. With respect to what I ha s ve on called the fu i n direct a ction s of changed conditions, namely, through the reproductive system ; being affected, we may infer that variability is thus induced, partly from the fact of this system app b e ar ing to b e far mo xt re mely s usc e p nsi ti bl v e t han any o ther part of the organisation, to the action of any change in the conditions , and partly from the similarity, as Kölreuter 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 s li f ght chang e s 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 in the many cases when the male and female unite. How many animals there are which will not breed, though living long und k e r no p t very in c an a l m os t fre e confinemen s t ate in their native country! This is generally , but erroneously, attributed to vitiated instincts ; . but how m M any cultivated plants display the utmost vigour, and yet rarely or never seed! In some few such cases it has been disc f o vere un d out that a very trifling change s , such as a little more or less water at some particular period of growth, will determine whether or not the a plant s will produc e ts a seed s . I cannot here giv e nter on the copious 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 just mention that carnivorous animals, even from the tropics, breed in this country pretty freely under confinement, with the exception of the plantigrades or bear family , which seldom produce young ; whereas , carnivorous birds, with the rarest exceptions, hardly ever lay fertile eggs. Many exotic plants have pollen utterly worthless, in the same exact condition as in the most sterile hybrids. When, on the one hand, we see domesticated animals and plants, though often weak and sickly, yet breeding quite 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 in to act ing , we need not be surprised at this system, when it does act under confinement, acting not qu i te r regularly, and producing offspring n s o mewha t perfectly un like their parents or variable . Sterility has been said to be the bane of horticulture; but on this view we owe variability to the same cause which produces sterility; and variability is the source of all the choicest productions of the garden. I may add, that as some organisms will breed most freely under the most unnatural conditions (for instance, the rabbit s and ferret s kept in hutches), showing that their reproductive organ s ystem h a s re not b e en thu a s ily affected; so will some animals and plants withstand domestication or cultivation, and vary very slightly—perhaps hardly more than in a state of nature. A 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 could easily be given of "sporting plants;" as they are called by this term gardeners ;—that me is, of pl an ts which have suddenly produced a single bud or offset, w h i c t h suddenly assumes a new and sometimes v wid e r l y different character from that of the othe r e bud s t o f n the same plant. Suc T h ese bud variation s , as they may be named, can be propagated by graft ing s, offsets , &c., and sometimes by seed. The se "sports" are extremel y occur rare ly under nature, but are far from rare under cult ivation; and in this case we see that the t u re atment . of the parent ha A s a ffected a single bud o r offset, and not the ov u les or pollen. But it is the opinion of most physiologists that there is no essential difference between a bud and an ovule in their earliest stages of formation; so that, in fact, "sports" support my view, that variability may be largely attributed to the ovules or pollen, or to both, having been affected by the treatmen t of the parent prior to the act of conception. These cases m any how show th ous a t nds, v produced ye ar i a f t i er year on is not necessarily connected, as some authors have supposed, with the act of generation. Seedlings from the same frui t , and the young of the same litter, sometimes differ considerably from each other, though both the young and the pa re nts, e as Müll und er has remarked, have appare u n tly been exp if o sed to exactly the sa r m e conditions , has been kn o f wn sudden l if y to assum e a new character ; and th as buds on d is tinct tree s h , gr ow s how ing un der different conditions, have somet im p es yielded nearly the same variety—f or ins tan ce, buds on peach-trees producing nectarines, and buds on common roses producing moss-roses—we clearly see tha t the di natu re ct effects of the conditions is of l subord i f nat e import a r nc e in comparison with the l n a ws of tu re production, and of growth, and of inheritance; for had the action of the c o nditions been di r ect, if g an y of the young had var i ed, all would probably have varied sm in the same manner. To judge how much, in the case of any variation, we should attribute to the direct action of heat, moisture, light, food, &c., is most difficult: my impression is, that with animals such agencies have produced very little direct effect, though apparently more in the case of plants. Un de r this point of view, Mr. Buckman's recent experiments on plants s ar e em extremely valuable. When all or nearly all the individuals exposed to certain conditions are affec te d in the same way, the change at fi r st appears to be directly due to such conditions; but in some cases it can be shown that quite opposite conditions produce si mi l ning e a r ch anges of structure. Nevertheless some slight amount of change may, I think, be attributed to the direct action of the conditions of life—as, in some cases, increased size from amount of food, colour from particular kinds form of food and or from light, v a riatio n d ;— perhaps of not more importance than the na t ure of the spark, by w hic kne h a ma ss of f combustible matter is ignited, has in determining the nat ur e of the f r lames. Effects o m climate. f Habit a nd of the Use or Disuse of Parts; Corre l s ated Variati o n; Inheritance. Changed ha bit s produce a n d inh e c r i d t ed influ e n ffe c e t , as in the period of the flowering with of plants when transported from one climate to another. In With animals the i ncreased use or disuse of par t s has had a more marked effect; for in sta flue nce , ; 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, than do the same bones in the wild - duck; and I presume that this change may be safely attributed to the domestic duck flying much less, and walking more, than its wild parent s . The great and inherited development of the udders in cows and goats in countries where they are habitually milked, in comparison with the s tate of thes e organs in other countries, is probably another instance of the effect s of use. Not a one single of our domestic animal s can be named which has not in some country drooping ears; and the view which has been suggested by some authors, that the drooping is due to the disuse of the muscles of the ear, from the animals not being seldom much alarmed by danger , seems probable. There are m M any laws regulat ing e variation, some few of which can be dimly seen, and will be hereafter b e b riefly ment d i on scuss ed. I will here only allude to what may be called correlat ed variat ion of growth . A Importa n y t change s in the embryo or larva will almost ce p r t ob a in b ly entail changes in the mature animal. In monstrosities, the correlations between quite distinct parts are very curious; and many instances are given in Isidore Geoffroy 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 w hich are entirely wh it e and h ave blue eyes are i ge n va e r i a b l ly deaf; but it has been lately stated by Mr. Tait that this is c onfined to the males. C olour and constitutional peculiarities go together, of which many remarkable cases could be given amongst animals and plants. From the facts collected by Heusinger, it appears that white sheep and pigs are d i ffere n tly affect jur ed f by ce r om tain plants, whilst dark- coloured individuals b escape: Professor Wyman has recentl y c ommunicated to me a good illustration of this fact; on asking some farm er s in Virginia how i t was that all their pigs were black, they informed him that the pigs ate the p ain t-root (Lachnanthes), which coloured their bones pink, and which caused the hoofs of all but the black v eg ari et ies to drop off; a nd one of the "crackers" (i.e. Virginia squatters) added, "we select the bl ack members of a litter for raising, as they alon e p have a g o od chance of l i so vi n s g . " 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, he will almost certainly unconsciously modify unintentionally other parts of the structure, owing to the mysterious laws of the correlation of growth . The result s of the various, quite unknown, or but dimly under s een tood laws of variation is are infinitely complex and diversified. It is well worth while carefully to study the several treatises published on some of our old cultivated plants, as on the hyacinth, potato, even the dahlia, &c.; and it is really surprising to note the endless points in of structure and constitution in which the varieties and sub-varieties differ slightly from each other. The whole organisation seems to have become plastic, and tends to depart s in some a s ma l l ight 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, is are endless. Dr. Prosper Lucas's treatise, in 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 alone . When a ny deviation of structure often appears not unfrequently , and we see it in the father and child, we cannot tell whether it may not be due to the same original cause having act ed ing on both; but when amongst 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 st several million individuals —and it reappears in the child, the mere doctrine of chances almost compels us to attribute its reappearance to inheritance. Every one must have heard of cases of albinism, prickly skin, hairy bodies, &c., appearing in several members of the same family. If strange and rare deviations of structure are t r u eal ly 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 qui for t h e most part unknown ; . n N o one can say why the s a me peculiarity in different individuals of the same species, or and in individuals of different species, is sometimes inherited and sometimes not so; why the child often reverts in certain character i s tics to its grandfather or grandmother or other m uch m ore 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 little 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 a peculiarity first appears, it tends to re- appear 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 silk - worm 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 i t s he 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 crossed offspring from a short-horned cow by a long-horned bull , the greater length of horn , 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 certa in variab ly 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 endeavoured 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 had ensued. It would be quite necessary , in order to prevent the effects of intercrossing, that only a single variety should have be en turned loose in its new home. Nevertheless, as our varieties certainly do occasionally revert in some of their characters to ancestral forms, it seems to me not improbable , that if we could succeed in naturalising, 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 d ef i rec ni t e 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, whilst kept under t unc h e s a m ng e d conditions, and whilst kept in a considerable body, so that free intercrossing might check, by blending together, any slight deviations in their of 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 favour of this view: to assert that we could not breed our cart and race-horses, long and short-horned cattle, and poultry of various breeds, and esculent vegetables, for an almost i u n f l i n m ite d number of generations, would be opposed to all experience. I may add, that when under nature the conditions of life do change, variations and reversions of c C haracter pr o bably f d D o occur; but natural s m e lec s ti on, as will hereafter be explained, will determine how far the new c haracters thus V ari etie s : difficulty of dist ing ui sh all ing be tween Varieties and S p ecies; origin of Domestic Varieties from one or mo re Specie s erved . When we look to the hereditary varieties or races of our domestic animals and plants, and compare them with species closely allied sp tog e ci th e s r , we generally perceive in each domestic race, as already remarked, less uniformity of character than in true species. Domestic races of the same species, also, of ten have a somewhat monstrous character; by which I mean, that, although differing from each other, and from the 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 all the species i u n der 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 races of the same species differ from each other in the same manner as , only in most cases in a lesser degree than, do the closely - allied species of the same genus in a state of nature . , I but th e differences in k mos t cases are less in degree. T his must be admitted , when we find as t hat rue, for the re are hardly any domestic races , either am o f ma n gst y animals or and plants , which have not been ranked by some c s om p e tent judges as mere varieties, and by other competent judges as the descendants of aboriginally distinct species , and by other competent judges as mere varieties . If any well marked distinction existed between a domestic race s and a species, this source of doubt c w ould not so perpetually recur. It has often been stated that domestic races do not differ from each other in characters of generic value. I think i t c ould an be shown that this statement is hardly not correct; but naturalists differ most widely much in determining what characters are of generic value; all such valuations being at present empirical. Moreover, on t W he n v i t is e xplained ho w of th g e nera origin of g at e u n d er n a ture, it w h i ch I sha ll pr b e se ntly giv e , n that we have no right to expect often to meet w f i th nd a generic amount of difference s in our domesticated p r odu a c tion e s. Whe I n we attempt ing to estimate the amount of structural difference between th alli e d domestic rac es of the same speci es, we are soon involved in doubt, from not knowing whether they h a v r e descended from one or several parent - species. This point, if it could be cleared up, would be interesting; if, for instance, it could be shown that the greyhound, bloodhound, terrier, spaniel, and bull-dog, which we all know propagate their kind so 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 very closely allied and natural species—for instance, of the many foxes—inhabiting 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 some a sm all part o f the difference is d u e to thei r b dogs hav e ing descended from any one wil d istinct species . ; I but, i n the case of s trongly marked races of s ome other domestic ated spe ra c i es, there is presumptive , or even strong , evidence , in favour of th at all the breeds h a v r e de i s cended from a s v i ngl e w ild 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 or and g uinea-f o wl ose , or the small power of endurance of warmth by the rein - deer, or of cold by the common camel, prevented their domestication? I cannot doubt that if other animals and plants, equal in 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 vary on an 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, I do not think it is not possible to come to any definite conclusion, whether they h a v r e 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 records, ti m ore es pecially , on the monuments of Egypt, and in the lake-habitations of Switzerland, much diversity in the breeds; and that some of the se ancient breeds closely resemble, pe o r haps are even identical with, those still existing. Even if But this on l a y t te h r ows fa r ba c kwards t he history of civilisation, and shows that animals were domesticated at a much earlier period than has hitherto been supposed. The lake-inhabitants o f ou Switzerla nd m cultivated several kinds of wheat and barley, the pea, the poppy f or oil, and flax; and they possessed several domesticated animals. They also carried on commerc e with other nations. All this clearly shows, as Heer has remarked, that they had at this early age progressed considerably in civilisation; and this again implies a long continued previous period of less advanced civilisation, during which the domesticated animals, kept by different tribes in different di strict s, might have varied and given rise to distinct races. Since the discovery of flint tools in the superficial formations of many parts of the world, all geologists believe that barbarian man existed at an enormously remote period; and we know that at the present day there is hard ly a nd generally tr ue than seems to me to i be the case, what does it show, but that so me of our b reeds originated there, four or five thousand ye ar s ago? But Mr. Horner's researches have rendered it in some degree pro ba ble that man s ro u fficiently s, civilized as not to have manufactured pottery existed in the valley of the Nile thirteen or fourteen thousand years ago; and who will pretend to say how long before these ancient periods, savages, like those of Tierra del Fuego or Australia, who possess a semi- domestic dog, m a y not have exis ted in at E least the do g ypt? . The wh o le subject must, I think, remain vague; neverthel s e ss, I may, without here ente ri n g on any details, state that, from geographical and other considerations, I th in k i of mos t highly pr o bable that f our domestic animals will probably for ever remain vague. But I may here state, that, looking to the domestic dogs of the whole world, I have , d aft e r a laboriou s c oll e ctio n ded of all known f r acts, c om e to the conclusion that several wild species . Knowing, as we do, that savages are very fond of taming C ani mals, it seems to me unlikely, in the case of the d og-genus, which is distributed in a wild state throughout the world, that since man first appeared one single species alone should æ have been tamed, and that their blood, in some cases mingled together, flows in the veins of our domestic at bre ed s . In regard to sheep and goats I can form no decided opinion. I should think, f F rom facts communicated to me by Mr. Blyth, on the habits, voice, and constitution, & and stru c ., ture of the humped Indian cattle, it is almost certain that the se y h a d re descended from a different aboriginal stock from our European cattle; and s om e veral competent judges believe that these latter have had m two or e th an on re e wild p rogenitors,—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 rese ar ch e n s of Professor Rü t imeyer . With respect to horses, from reasons which I cannot give her e giv e, I am doubtfully inclined to believe, in opposition to several authors, that all the races hav b e descended from l on e g wild s to ck. Mr. Blyth, whose opinion, from his large and varied stores of knowledge, I should value more th an that of almost any on e , th same species. Hav in g k s ept th ne a t rly all the English breeds of p the f o u w l try alive, hav ing bred and crossed them, and examined their skeletons, it appears to m e pr alm o st ce rtain that all ar e ded from the des c endants o mmon f the wild Indian fowl , ( Gallus bankiva ) ; and this is the conclusion of Mr. Blyth, and of others who have studied this bird in India . In regard to ducks and rabbits, th som e breeds of which differ mu c onsiderably h from each other in structure , I do no t he evi d oubt ence is clear that they all h a v r e all descended from the common wild duck and 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 in Great Britain eleven wild species of sheep peculiar to Great Br it ain ! When we bear in mind that Britain has now hardly not one peculiar mammal, and France but few distinct from those of Germany and conversely , and so with Hungary, Spain, &c., but that each of these kingdoms possesses several peculiar breeds of cattle, sheep, c., we must admit that many domestic breeds must have originated in Europe; for whence otherwise could they have been derived , as these several countries do not possess a number of peculiar species as distinct parent-stocks ? So it is in India. Even in the case of the breeds of the domestic dog s of th e w roug ho l ut th e world, which I fully admit h a ve p r obably e descended from several wild species, I it cannot be doubt ed that there has been an immense amount of inherited variation . ; W for w ho can will believe that animals closely resembling the Italian greyhound, the bloodhound, the bull-dog, pug-dog, or Blenheim spaniel, &c.—so unlike all wild Canidæ—ever existed freely 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 get 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, bull-dog, &c., in the wild state. Moreover, the possibility of making distinct races by crossing has been greatly exaggerated. Th Many cas e s a re ca o n b r e cord, n sh o doubt wing that a race may be modified by occasional crosses, if aided by the careful selection of th os e individual mongrel s , which present any the desired character; but t hat a race c o uld be obtain ed n a rac e arly intermediate between two ex qui t r e mely di ffere sti n c t races or spec e ies , I can hard wou l y d be lie ve ry difficult . Sir J. Sebright expressly experiment is ed for with this object, and failed. The offspring from the first cross between two pure breeds is tolerably and sometimes (as I have found with pigeons) ex qui t r e mely uniform in character , and everything seems simple enough; but when these mongrels are crossed one with another for several generations, hardly two of them will b ar e alike, and then the extreme difficulty , or rather utter hopelessness, of the task becomes apparent. Certainly, a breed intermediate between two very distinct breeds could not be got without extreme care and long-continued selection; nor can I find a single case on record of a per man ent race hav i ng been thus f orm e d. On s t he . 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 favoured with skins from several quarters of the world, more especially by the Hon. W. Elliot t from India, and by the Hon. C. Murray from Persia. Many treatises 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 and strictly 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 very long wings and tails, others singularly short tails. The barb is allied to the carrier, but, instead of a very long beak, has a very short and very broad one. The pouter 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 turbit has a very 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 œsophagus. 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, much elongated wing and tail feathers. The trumpeter and laugher, as their names express, utter a very different coo from the other breeds. The fantail has thirty or even forty tail - feathers, instead of twelve or fourteen , — the normal number in all the members of the great pigeon family ; and : 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 have be en 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 number of the caudal and sacral vertebræ vary in number ; as does the number of the ribs, together with their relative breadth and the presence of processes. The size and shape of the apertures in the sternum are highly variable; so is the degree of divergence and relative size of the two arms of the furcula. 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 œsophagus; 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 o f the fee oo t; the number of scutellæ 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 differs remarkably; , a s n d oes in some breeds the voice and disposition , differ remarkably . Lastly, in certain breeds, the males and females have come to differ to in a slight degree from each other. Altogether 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 , I think, 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, pouter, and fantail in the same genus; more especially as in each of these breeds several truly-inherited sub-breeds, or species , as he might have would call ed them, could be shown him. Great as are the differences are between the breeds of the pigeon s , I am fully convinced that the common opinion of naturalists is correct, namely, that all h a v r e 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 seven or eight 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 ing or willingly perch ing on trees. But besides C. 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 very 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 shores of the Mediterranean. Hence the supposed extermination of so many species having similar habits with the rock-pigeon seems to me 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 ever become wild or feral, though the dovecot-pigeon, which is the rock-pigeon in a very slightly altered state, has become feral in several places. Again, all recent experience shows that it is most difficult to get any wild animal s 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-civili z s ed man, as to be quite prolific under confinement. An argument , as it seems to me, of great weight, and applicable in several other cases, is, that the above-specified breeds, though agreeing generally with the wild rock-pigeon in constitution, habits, voice, colouring, and in most parts of their structure, with the wild rock-pigeon, yet are certainly highly abnormal in other parts of their structure : ; we may look in vain through out the whole great family of Columbidæ 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 J j acobin; 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-civili z s ed 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 seem to m ar e improbable in the highest degree. Some facts in regard to the colouring of pigeons well deserve consideration. The rock - pigeon is of a slaty-blue, and wit h as a white r loins; b u mp t ( the Indian sub-species, C. intermedia of Strickland, ha v s th i ng s i par t bluish ); . t T he tail has a terminal dark bar, with the bases of the outer feathers externally edged at the base with white ; . t T he wings have two black bars ; . s S ome semi-domestic breeds , and some apparently truly wild breeds , have, besides the two black bars, the wings chequered 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 two birds belonging to two or more distinct breeds are crossed, n on e ither of which is are blue or ha s ve any of the above-specified marks, the mongrel offspring are very apt suddenly to acquire these characters ; . f T o r give one instance , out of several which I have observed:— I crossed some uniformly white fantails , which breed very true, with some uniformly 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, and which notoriously breeds very true; the mongrels were dusky and mottled. I then crossed one of the mongrel barb-fantails with a mongrel barb-spot , and they produced mottled brown a nd black bird s; these I again crossed together, and one grandchild of the pure white fantail and pure black barb was of as beautiful a blue colour, with the white rump 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 h a v r e descended from the rock - pigeon. But if we deny this, we must make one of the two following highly improbable suppositions. Either, first ly , that all the several imagined aboriginal stocks were coloured and marked like the rock - pigeon, although no other existing species is thus coloured and marked, so that in each separate breed there might be a tendency to revert to the very same colours 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 w no instanc e is know n of no fa c t c r o unt ss e nancing the belief that the chil d d e v sc e r ndants revert s ing to some o a n e ancestor of foreign blood , removed by a greater number of generations. In a breed which has been crossed only once with some distinct breed , the tendency to rever sion t 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 with a distinct breed , and there is a tendency in bo th e pa b re nts ed to revert to a character , which h w as been 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 confounded in together by t reati ho se s who have written on inheritance. Lastly, the hybrids or mongrels from between all the domestic breeds of the pigeon s are perfectly fertile . , as I can state this from my own observations, purposely made , on the most distinct breeds. Now, it is difficult, per h aps impossible, to bring forw ard ly o a n e y case s have been ascertained with certainty of the hybrid off s pring fr o f m two an qu i mals cl t e arly distinct species of animals being themselves perfectly fertile. Some authors believe that long-continued domestication eliminates this strong tendency to sterility : f in species. F rom the history of the dog , I and of some other domestic animals, thi s co n k there clusion is some probab i l it y qu i n t his hypoth e sis correct , if applied to species closely related to g e ach o ther , though it is unsupported by a single experiment . But to extend the hypothes i s t so far as to suppose that species, aboriginally as distinct as carriers, tumblers, pouters, and fantails now are, should yield offspring perfectly fertile , inter se, seems t w o uld m b e rash in the extreme. From these several reasons, namely, — the improbability of man having formerly got made seven or eight supposed species of pigeons to breed freely under domestication; — these supposed species being quite unknown in a wild state, and their not having becom ing e a n o y where feral; — these species hav present ing certain very abnormal character s in certain respect s, as compared with all other Columbidæ, though so like in most other respects to the rock-pigeon in most respects ; —the occasional re-appearance of the blue colour and various black marks occasionally appearing in all the breeds, both when kept pure and when crossed; —and lastly, the mongrel offspring being perfectly fertile;—from these several reasons, taken together, I we may safely c an feel n o nclu d oubt e that all our domestic breeds h a v r e descended from the rock-pigeon or Columba livia with its geographical sub-species. In favour of this view, I may add, firstly, that the wild C. livia , or the rock-pigeon, has been found capable of domestication in Europe and in India; and that it agrees in habits 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 b va r i e t i wo rac e d s, more especially 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, b e u t not w een ith all the ext b re m e d s of structure . Thirdly, those characters which are mainly distinctive of each breed are in each eminently variable , for instance the wattle and length of beak of the carrier, the shortness of that of the tumbler, and the number of tail-feathers in the fantail , are in each breed eminently variable ; and the explanation of this fact will be obvious when we come to treat of s S election. Fourthly, pigeons have been watched , and tended 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 Ægyptian dynasty, about 3000 B.C., as was pointed out to me by Professor Lepsius; 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 Akber Khan in India, about the year 1600; never less than 20,000 pigeons were taken with the court. "The monarchs of Iran and Turan sent him some very rare birds ; " ; and, continues the courtly historian, "His Majesty by crossing the breeds, which method was never practised 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 favourable 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 well how tru e ly they br e ed, I felt fully as much difficulty in believing that since they coul ha d ever been domesticated they ha ve d des all pro ce n e ded from a common parent, as any naturalist could in coming to a similar conclusion in regard to the many species of finches, or other large 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 ever conversed, or whose treatises 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 raiser of Hereford cattle, whether his cattle might not have descended from l L ong-horns, 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 was not fully convinced that each main breed was descended from a distinct species. Van Mons, in his treatise on pears and apples, shows how utterly he disbelieves that the several sorts, for instance a 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 h a v r e 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 little effect may , perhaps, be attributed to the direct and definite action of the external conditions of life, and some little to habit; but he would be a bold man who would account by such agencies for the differences of between a dray and race horse, 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 animal's or plant's 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 tea zl s e l , with its hooks, which cannot be rivalled by any mechanical contrivance, is only a variety of the wild Dipsacus; 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 ancon sheep. But when we compare the dray-horse and race-horse, 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 very different ways; when we compare the game-cock, so pertinacious in battle, with other breeds so little quarrel - some, 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 sever m a l ny 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 ma k d e 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 som th e ir breeds of cattle and sheep. In order fully to realise what they have done, it is almost necessary to read several of the many treatises devoted to this subject, and to inspect the animals. Breeders habitually speak of an animal's organisation as something quite 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. Youatt, who was probably better acquainted with the works of agricultur al ists than almost any other individual, and who was himself a very good judge of an an imal s , speaks of the principle of selection as "that which enables the agriculturist, not only to modify the character of his flock, but to change it altogether. It is the magician's wand, by means of which he may summon into life whatever form and mould 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 it existence." That most skilful breeder, Sir John Sebright, used to say, with respect to pigeons, that "he would produce any given feather in three years, but it would take him six years to obtain head and beak." In Saxony the importance of the principle of selection in regard to merino sheep is so fully recognised, 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 effected is proved by the enormous prices given for animals with a good pedigree; and these have now 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 amongst 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; but its 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 skilful pigeon-fancier. The same principles are followed by horticulturists; but the variations are here often more abrupt. No one supposes that our choicest productions have been produced by a single variation from the aboriginal stock. We have proofs that this i ha s not been so in s om e veral 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. We see an astonishing improvement in many florists' flowers, when the flowers of the present day are compared with drawings made only twenty or thirty 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 this kind of selection is, in fact, a l ikewi s o e followed; for hardly any one is so careless as to all breed fr o w m his worst animals to breed . 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 heartsease are, and how alike the leaves; how much the fruit of the different kinds of gooseberries differ in size, colour, 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 s of correlat ed variat ion of growth , the importance of which should never be overlooked, will ensure some differences; but, as a general rule, I it cannot be doubt ed 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 treatises have been published on the subject; and the result , I may add, 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 acknowledgment of the importance of the principle i n work s of high a ck n tiquity owledged . 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 encyclopædia. Explicit rules are laid down by some of the Roman classical writers. From passages in Genesis, it is clear that the colour 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 match their draught cattle by colour, as do some of the Esquimaux their teams of dogs. Livingstone s how tate s t h ow much at good domestic breeds are highly valued by the negroes of 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 by 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, superior to anything of th e xist k in g d in the country. But, for our purpose, a kind form of Selection, which may be called Unconscious, and which results from every one 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 I we c m a nnot y doubt infer that this process, continued during centuries, would improve and modify any breed, in the same way as Bakewell, Collins, &c., by this very same process, only carried on more methodically, did greatly modify, even during their own lifetimes, the forms and qualities of their cattle. Slow and insensible changes of this kind c ould an never be recognised unless actual measurements or careful drawings of the breeds in question ha d ve been made long ago, which m ight ay serve for comparison. In some cases, however, unchanged , or but little changed individuals of the same breed may b e found xist in less civilised districts, where the breed has been less improved. There is reason to believe that King Charles's 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, been chiefly effected by crosses with the fox - hound; but what concerns us is, that the change has been effected unconsciously and gradually, and yet so effectually, that, though the old Spanish pointer certainly came from Spain, Mr. Borrow has not seen, as I am informed by him, any native dog in Spain like our pointer. By a similar process of selection, and by careful training, the whole body of English racehorses have come to surpass in fleetness and size the parent Arab s tock , so that the latter, by the regulations for the Goodwood Races, are favoured 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 given in various old pigeon treatises of the former and present state of carrier s and tumbler s w p i th these breeds as now existin g eons in Britain, India, and Persia, we can , I think, clearly trace the stages through which they have insensibly passed, and come to differ so greatly from the rock-pigeon. Youatt gives an excellent illustration of the effects of a course of selection, which may be considered as unconscious ly followed , in so far that the breeders could never have expected , or even have wished , to have produce d the result which ensued—namely, the production of two distinct strains. The two flocks of Leicester sheep kept by Mr. Buckley and Mr. Burgess, as Mr. Youatt remarks, "have been purely bred from the original stock of Mr. Bakewell for upwards of fifty years. There is not a suspicion existing in the mind of any one at all acquainted with the subject , that 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 particularly 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 unconscious selection going on. We see the value set on animals even by the barbarians of Tierra del Fuego, by their killing and devouring their old women, in times of dearth, 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 recognised in the increased size and beauty which we now see in the varieties of the heartsease, rose, pelargonium, dahlia, and other plants, when compared with the older varieties or with their parent-stocks. No one would ever expect to get a first-rate heartsease or dahlia from the seed of a wild plant. No one would expect to raise a first-rate melting pear from the seed of the wild pear, though he might succeed from a poor seedling growing wild, if it had come from a garden-stock. The pear, 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 , I cannot doubt, 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 has chanced to appear, selecting it, and so onwards. But the gardeners of the classical period, who cultivated the best pear s which they could procure, never thought what splendid fruit we should eat; though we owe our excellent fruit, in some small degree, to their having naturally chosen and preserved the best varieties they could anywhere find. A large amount of change in our cultivated plants , thus slowly and unconsciously accumulated, explains, as I believe, the well-known fact, that in a vast number of cases we cannot recognise, 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 uncivilised 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 g acqu i v r e n d to by the plants in countries anciently civilised. In regard to the domestic animals kept by uncivilised 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 circumstanced, 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 wh at has been remarked b y some authors, namely, that 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 civilised countries. On the view here given of the all- 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, or only with much difficulty, any deviation of structure excepting such as is externally visible; and indeed he rarely cares for what is internal. He can never act by selection, excepting on variations which are first given to him in some slight degree by nature. No man would ever try to make a fantail , till he saw a pigeon with a tail developed in some slight degree in an unusual manner, or a pouter 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 fantail, 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 fantails had only fourteen tail-feathers somewhat expanded, like the present Java fantail, or like individuals of other and distinct breeds, in which as many as seventeen tail-feathers have been counted. Perhaps the first pouter-pigeon did not inflate its crop much more than the turbit now does the upper part of its œsophagus,—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 differences, and it is in human nature to value any novelty, however slight, in one ' s own possession. Nor must the value which would formerly have be en set on any slight differences in the individuals of the same species, be judged of by the value which would is now be set on them, after several breeds have once fairly been established. M It is known that with pigeons m any slight differences might, v a nd r i ndeed d ati o ns now occasionally appear , ari but the se amongst pigeons, which are rejected as faults or deviations from the standard of perfection of in each breed. The common goose has not given rise to any marked varieties; hence the T h oulouse and the common breed, which differ only in colour, that most fleeting of characters, have lately been exhibited as distinct at our poultry-shows. I think t T hese views fu appea r t her o explain what has sometimes been noticed—namely , that we know hardly a n o y thing 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 had a d ef ist in i c t e 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 i a n d i vidu m als slowly spread in the immediate neighbourhood. But as yet they will as yet hardly have a distinct name, and from being only slightly valued, their history will have be en disregarded. When further improved by the same slow and gradual process, they will spread more widely, and will g b e t recognised as something distinct and valuable, and will then probably first receive a provincial name. In semi-civilised countries, with little free communication, the spreading and knowledge of a ny new sub-breed w i ou l l d be a slow process. As soon as the points of value of the new sub-breed are once fully 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 state of civili s z ation 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 favourable to Man's Power of Selection. I must will now say a few words on the circumstances, favourable, or the reverse, to man ' s power of selection. A high degree of variability is obviously favourable, 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 ; . and h H ence , this co nu m es to be r is of the highest importance t f o r success. On this principle Marshall has formerly remarked, with respect to the sheep of parts of Yorkshire, that "as they generally belong to poor people, and are mostly in small lots, they never can be improved." On the other hand, nurserymen, from rais keep ing large stocks of the same plant s , are generally far more successful than amateurs in gett rais ing new and valuable varieties. The keeping of a A large number of individuals of a species i n an y country requ i res th m a t the species shou l d be or pla nt c an be rear ed u o n d ly wh er e favourabl th e conditions o f life, s o as to b r eed freely i ts propagatio n th a t re c fav ou nt r y able . When the individuals of any species are scanty, all th will b e individu al s lowed to breed , whatever their quality may be, will generally be allowed to breed, and this will effectually prevent selection. But probably the most important poi eleme nt of all, is , that the animal or plant should be so highly useful to man, or so much valued by hi m an , that the closest attention i s hould be paid to even the slightest deviation s in i t he s qualities or structure of each individual . Unless such attention be paid nothing can be effected. I have seen it gravely remarked, that it was most fortunate that the strawberry began to vary just when gardeners began to attend closely 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 , there appeared ( a w i ded by th some aid by crossing with distinct species) those many admirable varieties of the strawberry w ere raised w hich have b app e en a r ais ed during the last t h irty or forty ye a lf-centu r s y . In Wi th e case of animal s with separate sexe s, facility in preventing crosses is an important element of success 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; and this circumstance must have largely favoured the improvement and 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 h r ar d e ly ever see a distinct breed long kept up; such breeds as we do sometimes see are almost always imported from some other country , often from islands . 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, &c., may be attributed in main part to selection not having been brought into play: in cats, from 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 organisation, 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 afterwards 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 fleetness of any terrestrial animal, as this will be determined by the friction to be overcome, the weight of body to be carried, and the power of contraction in the muscular fibres. 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 distinct species of the same genera. Isidore Geoffroy St. Hilaire has proved this in regard to size, and so it is with colour and probably with the length of hair. With respect to fleetness, which depends on many bodily characters, Eclipse was far fleeter, and a dray-horse is incomparably stronger than 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 D d omestic R r aces of animals and plants. I believe t C ha t th ng e d conditions of life , are o f rom the h i ghest impo r tance in causing variability, both by acti ng directly on the organisati on , and indirectly by affecting the reproductive system , are so far of the highest importance as causing variability . I t do is not pro b e ab l iev e that variability is an inherent and necessary contingen cy t , under all circumstances , with all organic beings, as some authors have thought . The effects of variability are modified by various de gre ater or l es s force of inheritance and of reversion determine whether variations shall endure . Variability is governed by many unknown laws, more especially by that of which correlat ion of ed growth is probably the most important . Something , but how much we do not know, may be attributed to the d ef i rec ni t e action of the conditions of life. Some , perhaps a grea t hing , effect m ust ay be attributed to the[increased use and or disuse of parts . The final result is thus rendered infinitely complex. In some cases , I do not doubt that the intercrossing of species, aboriginally distinct , species appears to ha s ve played an important part in the origin of our domestic p b r o ee d uction s. When in any country several domestic breeds have once been establish form ed in any country , their occasional intercrossing, with the aid of selection, has, no doubt, largely aided in the formation of new sub-breeds; but the importance of the crossing of varieties has , I believe, been greatly much exaggerated, both in regard to animals and to those plants which are propagated by seed. In With plants which are temporarily propagated by cuttings, buds, &c., the importance of the crossing both of distinct species and of varieties is immense; for the cultivator may here quite disregard s the extreme variability both of hybrids and of mongrels, and the frequent sterility of hybrids; but the cases of plants not propagated by seed are of little importance to us, for their endurance is only temporary. Over all these causes of Change I am convinced that , the accumulative action of Selection, whether applied methodically and more quickly, or unconsciously and more slowly , but more efficiently, i seem s to have b y far een the predominant Power.