ON SOMATIC SEX-CHARACTERS 81 



almost completely disappear after the breeding 



season and reappear in the following season. In the 



interval the drake passes into a condition of plumage 



in which he resembles the female ; and this condition 



is known as ' eclipse.' The male plumage, therefore, 



in the drake has a history somewhat similar to that of 



the antlers in deer. Two investigations of the effects 



of castration on ducks and drakes have been recorded. 



H. D. Goodale 1 removed the generative organs from 



both drakes and ducks of the Rouen breed, which 



is strongly dimorphic in plumage. One drake was 



castrated in the early spring of 1909 when a little less 



than a year old. This bird did not assume the 



summer plumage in 1909, that is, did not pass into 



eclipse. It was in the nuptial plumage when 



castrated. This breeding or nuptial plumage is well 



known : it includes a white neck-ring, brilliant green 



feathers on the head, much claret on the breast, 



brilliant metallic blue on the wing, and two or more 



upward curled feathers on the tail. The drake 



mentioned above was accidentally killed in the 



spring of 1910. Another drake was castrated on 



August 8, 1909 : only the left testis was removed, 



the other being ligatured. At this time the bird 



would be in eclipse plumage. It appears from the 



description that it assumed the nuptial plumage in 



the winter of 1909, and did not pass into eclipse 



again in the summer of 1910. Thus in drakes the 



effect of castration is that the secondary sexual 



character remains permanently instead of being 



lost and renewed annually. Goodale, however, does 



not describe the moults in detail. In the natural 



1 ' Castration of Drakes.' Biol. Bulletin, Wood's Hole, Mass., vol. xx., 

 1910. 



F 



