RELATING TO SECONDARY SEXUAL CHARACTERS. 13 



CASTRATION OF F 2 HEN-FEATHERED MALES. 



The F 2 hen-feathered males from this cross could not be utilized until 

 they had begun to assume the adult plumage, since before that time 

 they were like the cock-feathered F 2 males. Consequently, the opera- 

 tion is more difficult and more dangerous to the bird. A good many 

 birds have died in consequence of the operation, but enough successful 

 operations (five) were made to show what the color of certain types of 

 hen-feathered bird would be when changed to cock-feathering. 



A hen-feathered male (No. 292) that was darker than the F x male 

 in fact, almost black, except for a yellow center in some of the dorsal 

 feathers that were mossy or penciled was castrated. The details 

 of characteristic feathers may be gathered from the feathers in plate 7, 

 figure 2. A corresponding set of the new feathers after castration, 2a, 

 are paired with the former. The castrated male in his new plumage 

 is shown in plate 2, figure 3. His dorsal surface is colored very much 

 as is the same region in the FI bird, but the breast is very much 

 darker, so that the bird as a whole presents a very different appearance 

 from the FI castrated male. A very small white mass was found 

 when the bird was killed in place of the old testis, composed, in sec- 

 tions, of a reticulated mass of cells that look like old broken-down 

 follicles of testicular tubules with a few cell-layers lining the tubules. 



An F 2 male (68) also had dark feathers (plate 3, figure 2, and plate 

 9, figure 1) . The castrated male in his new plumage is represented in 

 plate 3, figure 3. Here again the upper surface is much like that of the 

 last castrate, and also like that of the F! castrate. The breast has 

 changed much less than the back; the centers of the feather are brown 

 with a black margin and a black band at the tip. The exposed 

 portion of the secondaries and the coverts are not so brown as in the 

 last bird. The spurs of this bird were bent back, looking like the 

 horns of a ram. When killed and examined, several small white pieces, 

 that looked like pieces of testes, were found in the abdominal cavity 

 near the old attachment of the testis. A histological study showed that 

 these pieces contained tubular tissue apparently testicular, but with- 

 out germ-cells. 



Another F 2 male (Band No. 221) was yellow in general color, the 

 feathers being irregularly penciled. After castration (plate 3, figure 4) 

 the bird became red above and deep brown below; the tail and 

 coverts were black. 



A pale-yellow hen-feathered bird (No. 218) was also castrated. 

 Here also the change was most conspicuous over the upper surface, 

 not only in a greater depth of color than elsewhere, but in the shape, 

 etc., of the feathers. On the breast the original yellow color remains, 

 but is slightly deepened. When killed and opened (May 14, 1919), 

 a few small, whitish pieces were found. When these were sectioned it 

 was seen that they were made up, for the most part, of tubules look- 



