16 GONADECTOMY IN RELATION TO THE SECONDARY 



the bird soon lost the juvenile coat and developed the adult coat of the 

 male of this variety, which has a silver-gray breast (sometimes sUghtly 

 tinged with purple) instead of the ruddy breast of the mallard, though 

 the other secondary sexual characters are the same. The new coat of 

 the duck was imperfect in many respects, but there was not the slight- 

 est doubt of its general character. No sooner had the feathers of this 

 coat become fully mature than it was lost, being replaced by a coat like 

 that of the sunmier coat of the male of this variety. That it was neither 

 a juvenile nor female coat is shown by two things: First, a few feathers 

 were vermiculated, a characteristic of the male's summer coat; second, 

 this coat was replaced early in the autumn by the typical male plumage 

 of this variety. In the summers of 1914 and 1915 the change to the 

 summer plumage was followed by a return to the breeding plumage 

 in the fall. 



Besides being the first instance of the clear assumption of the summer 

 plumage of the male by a castrated female, this bird is interesting in 

 another point, i. e. she has never developed a good duck's voice. As 

 already pointed out, only the female gives voice to the famihar sono- 

 rous quack. The drake never quacks, but produces a sound that can 

 best be described as a whispered "qua." No. 182 has never been able 

 to produce anything more than a broken quack, a sound best described 

 as intermediate between that of the male and female, except when 

 handled or otherwise subjected to special stimulus. Ordinarily she 

 simply whispers "qua, qua," very much as the drake does. 



In two respects, then, viz, assumption of summer plumage and im- 

 perfect voice, this individual approaches more closely to the male than 

 any bird previously operated on. Both the site of the ovary and the 

 corresponding region on the right side were examined in the autumn 

 of 1915 by means of an operation. They were entirely empty. 



Nos. 4 and 116. These two have been selected for description because 

 they represent a different and important type of result following removal 

 of the ovary. In addition, No. 4 is the oldest female from which an 

 ovary has been successfully removed. As she has been described 

 rather fully in an earlier paper, only a brief summary of the case will be 

 given here. The first operation was made when the bird was nearly a 

 year old. She was laying regularly immediately previous to the opera- 

 tion and in its course an egg with shell membranes fully formed 

 was removed from the oviduct. The anterior half of the latter was 

 also removed. By means of a second operation, August 22, 1912, it 

 was ascertained that no trace of the ovary was present on the left side, 

 nor as far as could be determined on the right, though a thorough ex- 

 amination of this side was impossible from the opening made on the 

 left. The bird is alive at date of writing, December 3, 1915. The 

 development of male characters has been very slight as compared to 

 the cases just described. She is clearly in an intermediate condition, 



