RELATING TO SECONDARY SEXUAL CHARACTERS. 9 



testis had been left behind and had regenerated. As it enlarged the new 

 feathers were affected so that the plumage returned towards the normal 

 type. The pieces of testis were removed and a few feathers plucked 

 out. The new feathers that came in were typically cock-feathered, 

 and, as the molting proceeded during the winter and spring, the bird 

 became cock-feathered for a second time as shown in photograph 

 (plate 5, figure 6) and by the feathers in plate 8, Ic, 2c, 3c, 4c. Here, 

 then, is an excellent example of the connection between the gonad and 

 the condition of the plumage. On opening this bird (May 1919) no 

 pieces of testes were found. There was a very small whitish lump at 

 the situs of the old testes, which, when sectioned, showed some gland- 

 ular-like tissue, not in tubules, and no evidence of testicular tissue. 



Three other younger Sebrights of the same stock were successfully 

 castrated. They were hatched in June or July and castrated in 

 November of the same year. They remained quite small birds, despite 

 their elongation due to the long tail and tail coverts that they devel- 

 oped. One of these birds in his cock-feathered plumage is shown in 

 plate 3, figure 1. One has died, the other two are alive and markedly 

 cock-feathered, as shown in plate 6, figure 2a. All three birds were 

 dark red-brown, much more so than the two preceding cases, especially 

 the first case. This color difference might be attributed to the earlier 

 age of the three birds when operated upon, or to a more complete 

 (or less complete) operation involving perhaps neighboring parts, or 

 to the birds having a somewhat different genetic composition (i. e., 

 modifying factors). There is no special reason why the operation if 

 performed early should have a different result on feathers that develop 

 after the bird is of adult age. Goodale has suggested that there may 

 be organs in the vicinity of the testis that have some influence on the 

 kind of plumage produced, and if there are such organs they might be 

 removed in one bird and accidentally left in another. It would not, 

 however, be probable that the bird operated on at first had received 

 one treatment and the later ones the other treatment. It seems to me 

 more probable that the birds have come from different genetic strains, 

 and that this genetic difference gives a more plausible explanation 

 of the darker cock-feathered plimaage. Goodale observed, for the first 

 time I think, that the largest wing coverts of the castrated cock be- 

 come longer. I looked, therefore, with some interest at the condition 

 of these same feathers in the castrated Sebrights. As shown in plate 

 10, figures 1, la, these feathers are also longer and narrower in the cas- 

 trated Sebright than in the normal bird. 



The true tail feathers of the capon are said to be longer than those of 

 the cock. This holds also for the tail feathers of all of my castrated 

 Sebrights. Their true tail feathers are considerably longer than those 

 of the normal male, as seen by pulling them out and comparing the 

 two. Their length is concealed while on the bird by the excessively 

 long coverts that appear after castration. 



