THE EFFECTS OF CASTRATION 135 



A similar operation was also carried out on females. 

 Three Herdwick ewe lambs (about 3 months old) were 

 operated upon. After ovariotomy, the animals were 

 kept for 17 months, but no horns appeared, although 

 in one, small scurs developed, in the other two scarcely 

 even these. It is clear that the removal of the ovaries 

 does not lead to the development of horns like those 

 in the male. 



Now, the interpretation of this case can be made 

 only when taken in connection with experiments in 

 heredity. There is a crucial experiment that bears on 

 this question. Arkell found when a Merino ewe (a race 

 with horned males and hornless females) was bred to a 

 ram of a hornless breed, that the sons had horns. In 

 this case the factor for horns must have come from the 

 hornless mother, while the development of the horns was 

 made possible by the presence of the male glands. It 

 is evident therefore in the castration experiment that 

 a factor for horns is inherited by both sexes, but in order 

 that the horns may develop fully, the male glands must 

 be present and functional. 



In the Dorset, both sexes are horned, the horns of the 

 females are lighter and smaller than the horns of the 

 ram (Fig. 68). In the castrated males the horns are 

 like those of the females. In this case we must sup- 

 pose that the hereditary factor for horns suffices to 

 carry them to the point in development reached by the 

 females. To carry them further the presence of the sex 

 glands of the male is necessary. 



In the case of the hornless breeds I do not know of 

 any evidence from castration or ovariotomy. We may 

 suppose, either that the factor for horns is absent ; or, 



