Чарльз Дарвин
The Variation of Animals and Plants under Domestication — Volume 1
The stripes are variable in colour, but are always darker than the rest of the body. They do not by any means always coexist on the different parts of the body: the legs may be striped without any shoulder-stripe, or the converse case, which is rarer, may occur; but I have never heard of either shoulder or leg-stripes without the spinal stripe. The latter is by far the commonest of all the stripes, as might have been expected, as it characterises the other seven or eight species of the genus. It is remarkable that so trifling a character as the shoulder-stripe being double or triple should occur in such different breeds as Welch and Devonshire ponies, the Shan pony, heavy cart-horses, light South American horses, and the lanky Kattywar breed. Colonel Hamilton Smith believes that one of his five supposed primitive stocks was dun-coloured and striped; and that the stripes in all the other breeds result from ancient crosses with this one primitive dun; but it is extremely improbable that different breeds living in such distant quarters of the world should all have been crossed with any one aboriginally distinct stock. Nor have we any reason to believe that the effects of a cross at a very remote period would be propagated for so many generations as is implied on this view.
With respect to the primitive colour of the horse having been dun, Colonel Hamilton Smith (2/41. 'Nat. Library' volume 12 1841 pages 109, 156 to 163, 280, 281. Cream-colour, passing into Isabella (i.e. the colour of the dirty linen of Queen Isabella), seems to have been common in ancient times. See also Pallas's account of the wild horses of the East, who speaks of dun and brown as the prevalent colours. In the Icelandic sagas, which were committed to writing in the twelfth century, dun-coloured horses with a black spinal stripe are mentioned; see Dasent's translation volume 1 page 169.) has collected a large body of evidence showing that this tint was common in the East as far back as the time of Alexander, and that the wild horses of Western Asia and Eastern Europe now are, or recently were, of various shades of dun. It seems that not very long ago a wild breed of dun- coloured horses with a spinal stripe was preserved in the royal parks in Prussia. I hear from Hungary that the inhabitants of that country look at the duns with a spinal stripe as the aboriginal stock, and so it is in Norway. Dun-coloured ponies are not rare in the mountainous parts of Devonshire, Wales, and Scotland, where the aboriginal breed would have the best chance of being preserved. In South America in the time of Azara, when the horse had been feral for about 250 years, 90 out of 100 horses were "bai-chatains," and the remaining ten were "zains," that is brown; not more than one in 2000 being black. In North America the feral horses show a strong tendency to become roans of various shades; but in certain parts, as I hear from Dr. Canfield, they are mostly duns and striped. (2/42. Azara 'Quadrupedes du Paraguay' tome 2 page 307. In North America Catlin (volume 2 page 57) describes the wild horses, believed to have descended from the Spanish horses of Mexico, as of all colours, black, grey, roan, and roan pied with sorrel. F. Michaux 'Travels in North America' English translation page 235, describes two wild horses from Mexico as roan. In the Falkland Islands, where the horse has been feral only between 60 and 70 years, I was told that roans and iron-greys were the prevalent colours. These several facts show that horses do not soon revert to any uniform colour.)
In the following chapters on the Pigeon we shall see that a blue bird is occasionally produced by pure breeds of various colours and that when this occurs certain black marks invariably appear on the wings and tail; so again, when variously coloured breeds are crossed, blue birds with the same black marks are frequently produced. We shall further see that these facts are explained by, and afford strong evidence in favour of, the view that all the breeds are descended from the rock-pigeon, or Columba livia, which is thus coloured and marked. But the appearance of the stripes on the various breeds of the horse, when of a dun colour, does not afford nearly such good evidence of their descent from a single primitive stock as in the case of the pigeon: because no horse certainly wild is known as a standard of comparison; because the stripes when they appear are variable in character; because there is far from sufficient evidence that the crossing of distinct breeds produces stripes, and lastly, because all the species of the genus Equus have the spinal stripe, and several species have shoulder and leg stripes. Nevertheless the similarity in the most distinct breeds in their general range of colour, in their dappling, and in the occasional appearance, especially in duns, of leg-stripes and of double or triple shoulder-stripes, taken together, indicate the probability of the descent of all the existing races from a single, dun-coloured, more or less striped, primitive stock, to which our horses occasionally revert.
THE ASS.
Four species of Asses, besides three zebras, have been described by naturalists. There is now little doubt that our domesticated animal is descended from the Equus taeniopus of Abyssinia. (2/43. Dr. Sclater in 'Proc. Zoolog. Soc.' 1862 page 164. Dr. Hartmann says ('Annalen der Landw.' b. 44 page 222) that this animal in its wild state is not always striped across the legs.) The ass is sometimes advanced as an instance of an animal domesticated, as we know by the Old Testament, from an ancient period, which has varied only in a very slight degree. But this is by no means strictly true; for in Syria alone there are four breeds (2/44. W.C. Martin 'History of the Horse' 1845 page 207.); first, a light and graceful animal, with an agreeable gait, used by ladies; secondly, an Arab breed reserved exclusively for the saddle; thirdly, a stouter animal used for ploughing and various purposes; and lastly, the large Damascus breed, with a peculiarly long body and ears. In the South of France also there are several breeds, and one of extraordinary size, some individuals being as tall as full-sized horses. Although the ass in England is by no means uniform in appearance, distinct breeds have not been formed. This may probably be accounted for by the animal being kept chiefly by poor persons, who do not rear large numbers, nor carefully match and select the young. For, as we shall see in a future chapter, the ass can with ease be greatly improved in size and strength by careful selection, combined no doubt with good food; and we may infer that all its other characters would be equally amenable to selection. The small size of the ass in England and Northern Europe is apparently due far more to want of care in breeding than to cold; for in Western India, where the ass is used as a beast of burden by some of the lower castes, it is not much larger than a Newfoundland dog, "being generally not more than from twenty to thirty inches high." (2/45. Col. Sykes Cat. of Mammalia 'Proc. Zoolog. Soc.' July 12, 1831. Williamson 'Oriental Field Sports' volume 2 quoted by Martin page 206.)
The ass varies greatly in colour; and its legs, especially the fore-legs, both in England and other countries — for instance, in China — are occasionally barred more plainly than those of dun-coloured horses. Thirteen or fourteen transverse stripes have been counted on both the fore and hind legs. With the horse the occasional appearance of leg-stripes was accounted for by reversion to a supposed parent-form, and in the case of the ass we may confidently believe in this explanation, as E. taeniopus is known to be barred, though only in a slight degree, and not quite invariably. The stripes are believed to occur most frequently and to be plainest on the legs of the domestic ass during early youth (2/46. Blyth in 'Charlesworth's Mag. of Nat. Hist.' vol 4 1840 page 83. I have also been assured by a breeder that this is the case.), as likewise occurs with the horse. The shoulder-stripe, which is so eminently characteristic of the species, is nevertheless variable in breadth, length, and manner of termination. I have measured one four times as broad as another, and some more than twice as long as others. In one light-grey ass the shoulder- stripe was only six inches in length, and as thin as a piece of string; and in another animal of the same colour there was only a dusky shade representing a stripe. I have heard of three white asses, not albinoes, with no trace of shoulder or spinal stripes (2/47. One case is given by Martin 'The Horse' page 205.); and I have seen nine other asses with no shoulder-stripe, and some of them had no spinal stripe. Three of the nine were light-greys, one a dark-grey, another grey passing into reddish-roan, and the others were brown, two being tinted on parts of their bodies with a reddish or bay shade. If therefore grey and reddish-brown asses had been steadily selected and bred from, the shoulder stripe would probably have been lost almost as generally and completely as in the case of the horse.
The shoulder stripe on the ass is sometimes double, and Mr. Blyth has seen even three or four parallel stripes. (2/48. 'Journal As. Soc. of Bengal' volume 28 1860 page 231. Martin on the Horse page 205.) I have observed in ten cases shoulder-stripes abruptly truncated at the lower end, with the anterior angle produced into a tapering point, precisely as in the above dun Devonshire pony. I have seen three cases of the terminal portion abruptly and angularly bent; and have seen and heard of four cases of a distinct though slight forking of the stripe. In Syria, Dr. Hooker and his party observed for me no less than five similar instances of the shoulder- stripe plainly bifurcating over the fore leg. In the common mule it likewise sometimes bifurcates. When I first noticed the forking and angular bending of the shoulder-stripe, I had seen enough of the stripes in the various equine species to feel convinced that even a character so unimportant as this had a distinct meaning, and was thus led to attend to the subject. I now find that in the E. burchellii and quagga, the stripe which corresponds with the shoulder-stripe of the ass, as well as some of the stripes on the neck, bifurcate, and that some of those near the shoulder have their extremities bent angularly backwards. The bifurcation and angular bending of the stripes on the shoulders apparently are connected with the nearly upright stripes on the sides of the body and neck changing their direction and becoming transverse on the legs. Finally, we see that the presence of shoulder, leg, and spinal stripes in the horse, — their occasional absence in the ass, — the occurrence of double and triple shoulder-stripes in both animals, and the similar manner in which these stripes terminate downwards, — are all cases of analogous variation in the horse and ass. These cases are probably not due to similar conditions acting on similar constitutions, but to a partial reversion in colour to the common progenitor of the genus. We shall hereafter return to this subject, and discuss it more fully.
CHAPTER 1.III
PIGS — CATTLE — SHEEP — GOATS.
PIGS BELONG TO TWO DISTINCT TYPES, SUS SCROFA AND INDICUS. TORFSCHWEIN. JAPAN PIGS. FERTILITY OF CROSSED PIGS. CHANGES IN THE SKULL OF THE HIGHLY CULTIVATED RACES. CONVERGENCE OF CHARACTER. GESTATION. SOLID-HOOFED SWINE. CURIOUS APPENDAGES TO THE JAWS. DECREASE IN SIZE OF THE TUSKS. YOUNG PIGS LONGITUDINALLY STRIPED. FERAL PIGS. CROSSED BREEDS.
CATTLE. ZEBU A DISTINCT SPECIES. EUROPEAN CATTLE PROBABLY DESCENDED FROM THREE WILD FORMS. ALL THE RACES NOW FERTILE TOGETHER. BRITISH PARK CATTLE. ON THE COLOUR OF THE ABORIGINAL SPECIES. CONSTITUTIONAL DIFFERENCES. SOUTH AFRICAN RACES. SOUTH AMERICAN RACES. NIATA CATTLE. ORIGIN OF THE VARIOUS RACES OF CATTLE.
SHEEP. REMARKABLE RACES OF. VARIATIONS ATTACHED TO THE MALE SEX. ADAPTATIONS TO VARIOUS CONDITIONS. GESTATION OF. CHANGES IN THE WOOL. SEMI-MONSTROUS BREEDS.
GOATS. REMARKABLE VARIATIONS OF.
The breeds of the pig have recently been more closely studied, though much still remains to be done, than those of almost any other domesticated animal. This has been effected by Hermann von Nathusius in two admirable works, especially in the later one on the Skulls of the several races, and by Rutimeyer in his celebrated Fauna of the ancient Swiss lake-dwellings. (3/1. Hermann von Nathusius 'Die Racen des Schweines' Berlin 1860; and 'Vorstudien fur Geschichte' etc. 'Schweineschadel' Berlin 1864. Rutimeyer 'Die Fauna der Pfahlbauten' Basel 1861.) Nathusius has shown that all the known breeds may be divided into two great groups: one resembling in all important respects and no doubt descended from the common wild boar; so that this may be called the Sus scrofa group. The other group differs in several important and constant osteological characters; its wild parent- form is unknown; the name given to it by Nathusius, according to the law of priority, is Sus indicus, of Pallas. This name must now be followed, though an unfortunate one, as the wild aboriginal does not inhabit India, and the best-known domesticated breeds have been imported from Siam and China.
First for the Sus scrofa breeds, or those resembling the common wild boar. These still exist, according to Nathusius ('Schweineschadel' s. 75), in various parts of central and northern Europe; formerly every kingdom (3/2. Nathusius 'Die Racen des Schweines' Berlin 1860. An excellent appendix is given with references to published and trustworthy drawings of the breeds of each country), and almost every province in Britain, possessed its own native breed; but these are now everywhere rapidly disappearing, being replaced by improved breeds crossed with the S. indicus form. The skull in the breeds of the S. scrofa type resembles, in all important respects, that of the European wild boar; but it has become ('Schweineschadel' s. 63-68) higher and broader relatively to its length; and the hinder part is more upright. The differences, however, are all variable in degree. The breeds which thus resemble S. scrofa in their essential skull characters differ conspicuously from each other in other respects, as in the length of the ears and legs, curvature of the ribs, colour, hairiness, size and proportions of the body.
The wild Sus scrofa has a wide range, namely, Europe, North Africa, as identified by osteological characters by Rutimeyer, and Hindostan, as similarly identified by Nathusius. But the wild boars inhabiting these several countries differ so much from each other in external characters, that they have been ranked by some naturalists as specifically distinct. Even within Hindostan these animals, according to Mr. Blyth, form very distinct races in the different districts; in the N. Western provinces, as I am informed by the Rev. R. Everest, the boar never exceeds 36 inches in height, whilst in Bengal one has been measured 44 inches in height. In Europe, Northern Africa, and Hindostan, domestic pigs have been known to cross with the wild native species (3/3. For Europe see Bechstein 'Naturgesch. Deutschlands' 1801 b. 1 s. 505. Several accounts have been published on the fertility of the offspring from wild and tame swine. See Burdach 'Physiology' and Godron 'De l'Espece' tome 1 page 370. For Africa 'Bull. de la Soc. d'Acclimat.' tome 4 page 389. For India see Nathusius 'Schweineschadel' s. 148.); and in Hindostan an accurate observer (3/4. Sir W. Elliot Catalogue of Mammalia 'Madras Journal of Lit. and Science' volume 10 page 219.), Sir Walter Elliot, after describing the differences between wild Indian and wild German boars, remarks that "the same differences are perceptible in the domesticated individuals of the two countries." We may therefore conclude that the breeds of the Sus scrofa type are descended from, or have been modified by crossing with, forms which may be ranked as geographical races, but which, according to some naturalists, ought to be ranked as distinct species.
Pigs of the Sus indicus type are best known to Englishmen under the form of the Chinese breed. The skull of S. indicus, as described by Nathusius, differs from that of S. scrofa in several minor respects, as in its greater breadth and in some details in the teeth; but chiefly in the shortness of the lachrymal bones, in the greater width of the fore part of the palate- bones, and in the divergence of the premolar teeth. It deserves especial notice that these latter characters are not gained, even in the least degree, by the domesticated forms of S. scrofa. After reading the remarks and descriptions given by Nathusius, it seems to me to be merely playing with words to doubt whether S. indicus ought to be ranked as a species; for the above-specified differences are more strongly marked than any that can be pointed out between, for instance, the fox and the wolf, or the ass and the horse. As already stated, S. indicus is not known in a wild state; but its domesticated forms, according to Nathusius, come near to S. vittatus of Java and some allied species. A pig found wild in the Aru islands ('Schweineschadel' s. 169) is apparently identical with S. indicus; but it is doubtful whether this is a truly native animal. The domesticated breeds of China, Cochin-China, and Siam belong to this type. The Roman or Neapolitan breed, the Andalusian, the Hungarian, and the "Krause" swine of Nathusius, inhabiting south-eastern Europe and Turkey, and having fine curly hair, and the small Swiss "Bundtnerschwein" of Rutimeyer, all agree in their more important skull-characters with S. indicus, and, as is supposed, have all been largely crossed with this form. Pigs of this type have existed during a long period on the shores of the Mediterranean, for a figure ('Schweineschadel' s. 142) closely resembling the existing Neapolitan pig was found in the buried city of Herculaneum.
Rutimeyer has made the remarkable discovery that there lived contemporaneously in Switzerland, during the Neolithic period, two domesticated forms, the S. scrofa, and the S. scrofa palustris or Torfschwein. Rutimeyer perceived that the latter approached the Eastern breeds, and, according to Nathusius, it certainly belongs to the S. indicus group; but Rutimeyer has subsequently shown that it differs in some well- marked characters. This author was formerly convinced that his Torfschwein existed as a wild animal during the first part of the Stone period, and was domesticated during a later part of the same period. (3/5. 'Pfahlbauten' s. 163 et passim.) Nathusius, whilst he fully admits the curious fact first observed by Rutimeyer, that the bones of domesticated and wild animals can be distinguished by their different aspect, yet, from special difficulties in the case of the bones of the pig ('Schweineschadel' s. 147), is not convinced of the truth of the above conclusion; and Rutimeyer himself seems now to feel some doubt. Other naturalists have also argued strongly on the same side as Nathusius. (3/6. See J.W. Schutz' interesting essay 'Zur Kenntniss des Torfschweins' 1868. This author believes that the Torfschwein is descended from a distinct species, the S. sennariensis of Central Africa.)
Several breeds, differing in the proportions of the body, in the length of the ears, in the nature of the hair, in colour, etc., come under the S. indicus type. Nor is this surprising, considering how ancient the domestication of this form has been both in Europe and in China. In this latter country the date is believed by an eminent Chinese scholar (3/7. Stan. Julien quoted by de Blainville 'Osteographie' page 163.) to go back at least 4900 years from the present time. This same scholar alludes to the existence of many local varieties of the pig in China; and at the present time the Chinese take extraordinary pains in feeding and tending their pigs, not even allowing them to walk from place to place. (3/8. Richardson 'Pigs, their Origin' etc. page 26.) Hence these pigs, as Nathusius has remarked (3/9. 'Die Racen des Schweines' s. 47, 64.), display in an eminent degree the characters of a highly-cultivated race, and hence, no doubt, their high value in the improvement of our European breeds. Nathusius makes a remarkable statement ('Schweineschadel' s. 138), that the infusion of the 1/32nd, or even of the 1/64th, part of the blood of S. indicus into a breed of S. scrofa, is sufficient plainly to modify the skull of the latter species. This singular fact may perhaps be accounted for by several of the chief distinctive characters of S. indicus, such as the shortness of the lachrymal bones, etc., being common to several species of the genus; for in crosses characters which are common to many species apparently tend to be prepotent over those appertaining to only a few species.
(FIGURE 2. HEAD OF JAPAN OR MASKED PIG. (Copied from Mr. Bartlett's paper in 'Proc. Zoolog. Soc.' 1861 page 263.))
The Japan pig (S. pliciceps of Gray), which was formerly exhibited in the Zoological Gardens, has an extraordinary appearance from its short head, broad forehead and nose, great fleshy ears, and deeply furrowed skin. Figure 2 is copied from that given by Mr. Bartlett. (3/10. 'Proc. Zoolog. Soc.' 1861 page 263.) Not only is the face furrowed, but thick folds of skin, which are harder than the other parts, almost like the plates on the Indian rhinoceros, hang about the shoulders and rump. It is coloured black, with white feet, and breeds true. That it has long been domesticated there can be little doubt; and this might have been inferred even from the fact that its young are not longitudinally striped; for this is a character common to all the species included within the genus Sus and the allied genera whilst in their natural state. (3/11. Sclater in 'Proc. Zoolog. Soc.' February 26, 1861.) Dr. Gray (3/12. 'Proc. Zoolog. Soc.' 1862 page 13. The skull has since been described much more fully by Professor Lucae in a very interesting essay, 'Der Schadel des Maskenschweines' 1870. He confirms the conclusion of von Nathusius on the relationship of this kind of pig.) has described the skull of this animal, which he ranks not only as a distinct species, but places it in a distinct section of the genus. Nathusius, however, after his careful study of the whole group, states positively ('Schweineschadel' s. 153-158). that the skull in all essential characters closely resembles that of the short-eared Chinese breed of the S. indicus type. Hence Nathusius considers the Japan pig as only a domesticated variety of S. indicus: if this really be the case, it is a wonderful instance of the amount of modification which can be effected under domestication.
Formerly there existed in the central islands of the Pacific Ocean a singular breed of pigs. These are described by the Rev. D. Tyerman and G. Bennett (3/13. 'Journal of Voyages and Travels from 1821 to 1829' volume 1 page 300.) as of small size, hump-backed, with a disproportionately long head, with short ears turned backwards, with a bushy tail not more than two inches in length, placed as if it grew from the back. Within half a century after the introduction of European and Chinese pigs into these islands, the native breed, according to the above authors, became almost completely lost by being repeatedly crossed with them. Secluded islands, as might have been expected, seem favourable for the production or retention of peculiar breeds; thus, in the Orkney Islands, the hogs have been described as very small, with erect and sharp ears, and "with an appearance altogether different from the hogs brought from the south." (3/14. Rev. G. Low 'Fauna Orcadensis' page 10. See also Dr. Hibbert's account of the pig of the Shetland Islands.)
Seeing how different the Chinese pigs, belonging to the Sus indicus type, are in their osteological characters and in external appearance from the pigs of the S. scrofa type, so that they must be considered specifically distinct, it is a fact well deserving attention, that Chinese and common pigs have been repeatedly crossed in various manners, with unimpaired fertility. One great breeder who had used pure Chinese pigs assured me that the fertility of the half-breeds inter se and of their recrossed progeny was actually increased; and this is the general belief of agriculturists. Again, the Japan pig or S. pliciceps of Gray is so distinct in appearance from all common pigs, that it stretches one's belief to the utmost to admit that it is simply a domestic variety; yet this breed has been found perfectly fertile with the Berkshire breed; and Mr. Eyton informs me that he paired a half-bred brother and sister and found them quite fertile together.
(FIGURE 3. HEAD OF WILD BOAR, AND OF "GOLDEN DAYS," a pig of the Yorkshire Large Breed; the latter from a photograph. (Copied from Sidney's edition of 'The Pig' by Youatt.))
The modification of the skull in the most highly cultivated races is wonderful. To appreciate the amount of change, Nathusius' work, with its excellent figures, should be studied. The whole of the exterior in all its parts has been altered: the hinder surface, instead of sloping backwards, is directed forwards, entailing many changes in other parts; the front of the head is deeply concave; the orbits have a different shape; the auditory meatus has a different direction and shape; the incisors of the upper and lower jaws do not touch each other, and they stand in both jaws beyond the plane of the molars; the canines of the upper jaw stand in front of those of the lower jaw, and this is a remarkable anomaly: the articular surfaces of the occipital condyles are so greatly changed in shape, that, as Nathusius remarks (s. 133), no naturalist, seeing this important part of the skull by itself, would suppose that it belonged to the genus Sus. These and various other modifications, as Nathusius observes, can hardly be considered as monstrosities, for they are not injurious, and are strictly inherited. The whole head is much shortened; thus, whilst in common breeds its length to that of the body is as 1 to 6, in the "cultur-racen" the proportion is as 1 to 9, and even recently as 1 to 11. (3/15. 'Die Racen des Schweines' s. 70.) Figure 3 (3/16. These woodcuts are copied from engravings given in Mr. S. Sidney's excellent edition of 'The Pig' by Youatt 1860. See pages 1, 16, 19.) of the head of a wild boar and of a sow from a photograph of the Yorkshire Large Breed, may aid in showing how greatly the head in a highly cultivated race has been modified and shortened.
Nathusius has well discussed the causes of the remarkable changes in the skull and shape of the body which the highly cultivated races have undergone. These modifications occur chiefly in the pure and crossed races of the S. indicus type; but their commencement may be clearly detected in the slightly improved breeds of the S. scrofa type. (3/17. 'Schweineschadel' s. 74, 135.) Nathusius states positively (s. 99, 103), as the result of common experience and of his experiments, that rich and abundant food, given during youth, tends by some direct action to make the head broader and shorter; and that poor food works a contrary result. He lays much stress on the fact that all wild and semi-domesticated pigs, in ploughing up the ground with their muzzles, have, whilst young, to exert the powerful muscles fixed to the hinder part of the head. In highly cultivated races this habit is no longer followed, and consequently the back of the skull becomes modified in shape, entailing other changes in other parts. There can hardly be a doubt that so great a change in habits would affect the skull; but it seems rather doubtful how far this will account for the greatly reduced length of the skull and for its concave front. It is well known (Nathusius himself advancing many cases, s. 104) that there is a strong tendency in many domestic animals — in bull- and pug-dogs, in the niata cattle, in sheep, in Polish fowls, short- faced tumbler pigeons, and in one variety of the carp — for the bones of the face to become greatly shortened. In the case of the dog, as H. Muller has shown, this seems caused by an abnormal state of the primordial cartilage. We may, however, readily admit that abundant and rich food supplied during many generations would give an inherited tendency to increased size of body, and that, from disuse, the limbs would become finer and shorter. (3/18. Nathusius 'Die Racen des Schweines' s. 71.) We shall in a future chapter see also that the skull and limbs are apparently in some manner correlated, so that any change in the one tends to affect the other.
Nathusius has remarked, and the observation is an interesting one, that the peculiar form of the skull and body in the most highly cultivated races is not characteristic of any one race, but is common to all when improved up to the same standard. Thus the large-bodied, long-eared, English breeds with a convex back, and the small-bodied, short-eared, Chinese breeds with a concave back, when bred to the same state of perfection, nearly resemble each other in the form of the head and body. This result, it appears, is partly due to similar causes of change acting on the several races, and partly to man breeding the pig for one sole purpose, namely, for the greatest amount of flesh and fat; so that selection has always tended towards one and the same end. With most domestic animals the result of selection has been divergence of character, here it has been convergence. (3/19. 'Die Racen des Schweines' s. 47. 'Schweineschadel' s. 104. Compare also the figures of the old Irish and the improved Irish breeds in Richardson on 'The Pig' 1847.)
