GENETIC TYPE AND THE ENDOCRINES 21 



Many of the varieties of domestic swine differ widely in 

 type and form from the wild hog and have been selected 

 chiefly for tendencies towards high accumulation of fat. There 

 is one variety, the Japan pig (Sus pliciceps, Gray), which is 

 an almost bulldog-St. Bernard combination in type. This hog- 

 has an extraordinary appearance, with shortened muzzle and 

 broad frontal region, a heavy fleshy condition of the ears, 

 and skin that is thickened and deeply furrowed into folds 

 about the neck and shoulders, suggesting in some respects the 

 condition in the bloodhound and St. Bernard dogs. The 

 Japan pig is an old and well established race, breeding true. 

 The highly modified skull has led some taxonomists to rank 

 it not only as a distinct species, but to place it in a separate 

 section of the genus. Others have considered it to be only 

 a domesticated variety of Sus indicus, a short-eared Chinese 

 breed. Darwin knew of all these breeds and felt that if the 

 latter interpretation were correct the Japan pig furnished a 

 wonderful example of the amount of modification which could 

 be effected under domestication. The modern interpretation 

 is that the Japan pig has arisen as a distinct mutant race. 



Not alone these mammalian forms, but the far removed 

 domestic fowls present wide diversity in size and type among 

 the various breeds throughout the world. Many of these 

 breeds are hybrid in wild origin and thus complicated in their 

 hereditary composition. In general it is believed that the 

 breeds of domestic fowl were probably derived from the small 

 wild Gallus bankiva of India in combination with the larger 

 Cochin fowl of Asia. There are at present giant races, 

 larger than either of these wild types, and dwarf and bantam 

 varieties, as well as the short legged creeper fowl, all showing 

 conditions closely comparable to the modified forms in mam- 

 mals. Landauer ('33) has recently shown that a homozygous 

 condition in the creeper fowl brings about an extreme state 

 of chondrodystrophy, giving badly deformed head and ex- 

 tremities in non-viable individuals. Some evidence of modi- 

 fied endocrine glands in these fowls has also been presented. 



