136 



HEREDITY AND SEX 



if present, some inhibitory factor must bring about sup- 

 pression of the horns. The former assumption seems 

 more probable, for, as I shall point out, certain experi- 

 ments in heredity indicate that no inhibitor is present 

 in hornless breeds. 



The series is completed by cases like that of 

 the eland and the reindeer. Both males and females 



9^' 



Fig. 69. — Fat-tailed hornless sheep (Ovis 

 aries steatopyga persicci). 



have well-developed horns. In this case the hereditary 

 factors suffice in themselves for the complete develop- 

 ment of horns, for even after castration the horns de- 

 velop. 



We have anticipated to some extent the conclusions 

 arrived at by breeding experiments in these races of 

 sheep. The best-known case is that of Wood, who 

 crossed horned Dorsets and hornless Suffolks. As 



