THE HORMONE THEORY 155 



white-ringed Formosan variety, P. torquaius, of the 

 Chinese pheasant. 1 On the left side this bird shows 

 the plumage, colour, and the spur of the male; on 

 the right leg there is no spur except the small rudi- 

 ment normally occurring in the hen. The difference 

 in plumage between the two sides, however, is not 

 complete. The white collar is strictly limited to the 

 left side, but the iridescent blue green of head and 

 neck is present on both sides, though more marked 

 on the left. Only a few male feathers appear in the 

 wing coverts of the left side. The breast feathers 

 are rufous, especially on the left side. The tail 

 coverts show marked male characters, more especially 

 on the left side. In the tail, however, the barred 

 character of the male is not present on one side, 

 absent on the other, but in most of the feathers is 

 confined to one, the outer side of each feather. With 

 regard to the gonads, in this bird a single organ was 

 found on the left side, i.e. in the position of the 

 ovary in normal females, and there was no trace of 

 a gonad on the right side. The organ present was 

 small, | inch long by | inch broad, and micro- 

 scopic sections showed in one part actively 

 growing areas of tubular gland structure in some 

 of which bodies like spermatozoa could be de- 

 tected, while in another were fibrous tissue with 

 degenerating cysts. The latter appear to have 

 been degenerating egg follicles. The author con- 

 cludes that the organ was originally a functional 

 ovary, and that the ovarian portion had atrophied 

 while a male portion had become functionally 

 active. 



1 C. J. Bond, ' Unilateral Development of Secondary Male Characters 

 in a Pheasant,' Journ. oj Genetics, vol. iii., 1914, 



