RELATING TO SECONDARY SEXUAL CHARACTERS. 11 



feather (6) had not yet completed its full growth. On the bow of the 

 wing a few intermediate feathers, like the one shown in 2a, were 

 present. (For comparison with normal and castrated feathers see 

 those on places 6 and 8.) 



An intermediate feather from the back is shown in 2a. For com- 

 parison with the old feathers from the same region see plate 6, fig. 2. 

 An intermediate saddle feather is shown in 2a. For comparison with 

 normal feathers from the same region see figure 2. A still later feather 

 from the castrated bird is shown in 26. The last was not yet com- 

 plete when removed from the bird. 



It will be noticed that the change after castration involves the color, 

 the shape, and the presence and absence of barbules in those parts of 

 the bird that are peculiar in the last respect. The transition in these 

 characters is quite sharp as sharp in fact as is compatible with the 

 passage from one structure to that of an entirely different kind without 

 any discontinuity of growth. Owing to the quickness of the response 

 shown by the feather, it will be possible to study more in detail the 

 length of time the secretion remains in the body of the bird after the 

 testes have been removed. 



CASTRATION OF F x HEN-FEATHERED MALES FROM SEBRIGHT 

 BY GAME. 



Hen-feathering is dominant to cock-feathering. As shown in plate 

 2, the FI male is almost as completely hen-feathered as is the male 

 Sebright. There is a somewhat greater color difference between the 

 FI male and FI female than between the Sebright male and female. 

 Two FI birds were castrated for me by Goodale. At the time of 

 operation, in the autumn of 1916, both birds were full grown, (plate 

 2, figure 1). After molting the old feathers, both birds appeared as 

 shown in plate 2, figure 4. Each is completely cock-feathered. The 

 plumage has also undergone a remarkable change in color. In general, 

 the color change is from yellow and black to reddish yellow. The 

 greatest change is over the upper surface. The sickle, covert, and tail 

 feathers are well formed and have now become iridescent black. The 

 breast has changed least of all. One bird died February 12, 1919. 

 When opened there was found on the left side a small white lump; 

 on the other side almost nothing. The lump was found to consist of 

 testicular tubules with loose glandular cells on its walls. 



The extent to which the change has taken place is best shown by 

 comparison of individual feathers from identical regions one before 

 and one after the new feathers (taken out two years later) have come 

 in (plate 7). The contrast between the old and new feathers of the 

 hackle, saddle, back, and wing-bow are the most striking. In all of 

 these the new feathers have become red on the exposed portion and the 

 margin is free from barbules, as in the cock bird. The increase in size 



