(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.

The Variation of Animals and Plants Under Domestication V1 Page 47

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Charles Darwin

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