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. Illustration: Fig. 3—Head of Wild Boar, and of “Golden Days,” a pig of the Yorkshire Large Breed 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.[15] The following woodcut[16] 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.