SEXUAL CHARACTERS OF SOME DOMESTIC BIRDS. 31 



that, though usually quiet and voiceless, he sometimes crows, sometimes 

 shows the male sexual reaction, and may brood chicks. (Plate vii, fig. G.) 

 There is another peculiarity of the capon that I have never seen 

 described, although it seems impossible that it could have escaped 

 notice. The first row of coverts covering the primaries become dispro- 

 portionately long, while the secondary coverts retain their normal pro- 

 portions. The disproportion is shown in plate vii, E. This increased 

 size of the primary coverts is of considerable importance, since it indi- 

 cates that the feathers differ in their response to the secretions of the 

 testes. While, as stated above, the feathers of the capon in general 

 are longer than those of the cock, the coverts grow much longer than 

 any of the neighboring feathers. 



AGE IN RELATION TO GONADECTOMY. 



The age at which the operation is performed may influence the final 

 results in one of two ways: First, the character, such as a mature 

 feather, may have ceased growing and therefore be non-modifiable. 

 Secondly, it may be still growing, or it may resume its growth sub- 

 sequent to the operation, so that in either case there is the possi- 

 bility of modification. Moreover, age might influence the type of 

 modification through its action on other parts of the body. That is, 

 a bird castrated when 3 weeks old might give an entirely different 

 result from one castrated at 3 months, but thus far, aside from structures 

 which are no longer growing and therefore no longer subject to the 

 influence of the gonad, no constant relation to age has been observed. 



Since, however, the young bird is less differentiated than the older, 

 greater changes would be expected. If it were possible to destroy the 

 germ glands at the proper time during the embryonic life, the female 

 embryo possibly might become transformed somatically into a male. 



AGE OF THE FEATHER GERM IN RELATION TO THE TYPE OF 

 FEATHER DEVELOPED. 



It has happened in a number of instances that the female bird has 

 been molting at the time of the operation. Individual feathers from 

 such birds often show both male and female colors, color patterns, and 

 even shapes, the area occupied by each depending upon the age of the 

 feather germs; the younger the feather the larger the area of male 

 characters. The colors are often separated by a clear-cut transverse 

 fine in both ducks and chickens. The effect is more striking in feathers 

 from fowls than in those from ducks, largely because of the kind of 

 characters involved. The cleanest-cut instances have been observed in 

 Brown Leghorn pullets, particularly in the breast feathers, which are 

 salmon-colored in the normal female but black in the male. The 

 modified feathers are salmon-colored at the distal end, but at some 



