82 INFLUENCE OF HORMONES 



condition the drake must moult twice in the year, 

 once when he sheds the nuptial plumage, and again 

 when he drops the summer dress. Goodale insists, 

 from some idea about secondary sexual characters 

 which is not very obvious, that the eclipse or summer 

 plumage is not the same as that of the female. He 

 states that the male in summer plumage merely 

 mimics the female but does not become entirely like 

 her. In certain parts of the body there are no 

 modifications toward the female type. In others, 

 i.e. head, breast, and keel region, the feathers of the 

 male become quite like those of the female. ' It 

 can hardly be maintained that this is an example 

 of assumption by the male of the female's plumage, 

 especially as the presence of the testis is necessary for 

 its appearance.' The idea here seems to be that since 

 the eclipse plumage is only assumed when the testis 

 is present, therefore it must be a male character. 



Out of five females on which the operation was 

 performed only two lived more than a few days 

 afterwards. One of these (a) was castrated in the 

 spring of 1909 when a little less than a year old, the 

 other (6) on August 13 when twelve weeks old. In 

 October 1909 they showed no marked modifications. 

 In July 1910 it was noticed that they had the male 

 curled feathers in the tail, and (a) had breast feathers 

 similar to those of the male in summer plumage, 

 (6) was rather more strongly modified : she had a 

 very narrow white neck-ring, and breast feathers 

 distinctly of male type. The next moult began in 

 September, and in November was well advanced. 

 On the whole (a) had made little advance towards 

 the male type, but (b) closely resembled the male 

 in nuptial plumage. It had brilliant green feathers 



