Secondary Sexual Characters 435 



as to make it doubtful if the development of horns was due to 

 this defect. Cases of this sort are not of much value, since it is 

 possible that the abnormalities observed may both be due to 

 some abnormal condition of the whole and are not connected 

 as cause and effect. 



The best-known cases in which the castrated female assumes 

 the characters of the male are found in poultry. Many in- 

 stances of this sort have been recorded.^ It has also been 

 observed that when female birds, such as pheasants, fowls, par- 

 tridges, peacocks, and ducks, become old, they may assume the 

 secondary sexual characters of the male. Darwin cites the case 

 of a duck ten years old that assumed the perfect winter and sum- 

 mer plumage of the drake. Waterton gives the case of a hen 

 that had ceased laying and had assumed the plumage, spurs, 

 voice, and disposition of the cock. This evidence points clearly 

 to -the possibihty of the castrated female assuming the charac- 

 ters of the male. Whether the converse is true for the male is, 

 as we have seen, more doubtful, but the possibility of its being 

 true must be admitted. 



If the characters of the female are latent in the male, and those 

 of the male are latent in the female, as these and other facts seem 

 to show, the experiments with castration have an interesting 

 bearing on sex determination ; for if, as seems probable, the 

 male characters may develop in a castrated female despite the 

 fact that the female characters had already been developed, 

 it shows that the question of sex determination, even if deter- 

 mined in the egg, or even in the embryo, is not final and the con- 

 verse change may occur even at a late stage. If it should prove 

 true that in the vertebrates the castrated female develops male 

 characters, but the castrated male does not develop female char- 

 acters, but simply remains at a lower stage of development, we 

 might perhaps assume that the male condition in this group 

 is a further stage of the female condition. Internal or external 

 factors may determine whether the egg or embryo remains at a 

 given stage or undergoes a further change. If the former, a 



^ Darwin, "Animals and Plants," Chap. XIII. 



