98 HEREDITY AND EUGENICS 



tions. The condition appeared in both males and 

 females, but the bulls were not kept, so transmission 

 was only through the cows. About two calves in three 

 had the extra toe. The abnormality was confined 

 to the hind feet, except in one case. As the last 

 members of the strain were all males the breed was 

 lost. This instance of Polydactyly is very similar 

 to the last. The inheritance was evidently the same, 

 but the character itself show^s the interestinsr difference 

 that it is less extreme. It is confined to the hind feet, 

 except in one individual, whereas in Roberts's herd 

 it is present on all four feet, but is larger on the hind 

 feet. Such slight constant differences in abnormali- 

 ties are of fairly frequent occurrence, and they throw 

 an interesting sidelight on the structure of the germ 

 plasm and the almost infinite variety of the changes 

 which it can undergo. 



A very good case of syndactyly in ungulates is 

 that of the mule-foot hog, a type with solid instead of 

 cloven hoofs, which has long been known in the 

 Western States of America, and is also found in 

 Germany and elsewhere. Detlefsen and Carmichael 

 (1921) find that in crosses between a pure-bred mule- 

 foot boar and pure-bred Duroc-Jersey sows the 

 offspring, numbering about 250, were all black and 

 mule-footed like the sire. Later generations showed 

 that syndactyly was a simple dominant to normal, 

 and black to red of various shades. 



Bateson (p. 387) gives numerous data on the subject. 

 He states that solid hoofs in pigs is a relatively common 

 variation, that they are mentioned by Aristotle, 

 and are found in various parts of the world. Sir 

 N. Menzies at Rannock, Scotland, had a breed of such 

 hogs for forty years. They came from a pair, and 

 were black and of smaller size than the type, with 

 smaller ears. Their flesh was considered more sweet 

 and tender, and several hundred were bred at a time. 



