44 



GENETIC STUDIES ON A CAVY SPECIES CROSS. 



By mating fertile males to guinea-pigs and to hybrids of various 

 blood dilutions, progeny of the following classes have been obtained: 



The number of young, 241, is large, but when these are divided into 

 groups according to the color matings of their parents, there are but 

 few in each class of mating. As far as they go they corroborate 

 entirely the results procured with the female hybrids, previously given. 

 The peculiar, dark agouti (with ticked belly) of the fertile male hybrids 

 is similar also to that of the females in appearance and transmission. 



The appearance of these fertile hybrid males is important because of 

 the purely scientific interest in the study of fertility. A number of 

 recent workers have tried to establish fertile male cattaloes. Boyd 

 (1908) has reported on the dominance of the white face of the Hereford, 

 and the polled or hornless condition of the Angus, when crossed with 

 the American bison. The cattaloes lose the valuable coat when they 

 are continually mated to the domestic bull; and the cross with the 

 buffalo bull is frequently fatal to the female cattalo. The success in 

 getting the best quality of bison coats would lie in breeding them 

 together, according to Boyd. However, no half-blood bison are known 

 to be fertile. Iwanoff (1911) and Boyd have reason to believe that the 

 J bloods and | bloods are fertile. Boyd has successfully bred a j blood 

 hybrid bull. Iwanoff has examined the spermatozoa of a | blood 

 bison and reports that they are normally developed. He also alludes to 

 a successful mating between such a male and a I blood bison female, 

 and supposes that the offspring from this mating should prove to be 

 fertile. This may be the case in these hybrids, but if they are analo- 

 gous to the wild guinea-pig hybrids, as they seem to be, it would not 

 necessarily follow; for fertile hybrid males and females do not always 

 produce fertile young when mated inter se. Nevertheless, if the cross 

 between the wild and tame guinea-pig is at all comparable to the 

 ungulate species crosses, it is important to know that the same laws of 

 color inheritance obtain in crosses between the hybrids as in the crosses 

 of hybrid females to the parent stock. This would apply to such 



