96 THE GENETIC AND THE OPERATIVE EVIDENCE 



as the testes began to regenerate. When the regenerated pieces were 

 removed the bird became cock-feathered again. 



7. One Sebright male whose testes appear to have been completely 

 removed did not change the character of the plumage. No testes were 

 found on autopsy. It is suggested that some other endocrine organs 

 have taken over the function of the testes, but as yet none such can be 

 indicated. 



8. In one case an old hen-feathered (Fi) male began to change over 

 to cock-feathering. It was found that his testes had dwindled (prob- 

 ably through disease) to very small size (10 by 5 mm.). 



9. The Fi male of the cross between the Sebright and game is also 

 hen-feathered (plate 2, fig. 1). After castration he becomes cock- 

 feathered (plate 2, fig. 4) and shows thereby the genetic type of the 

 heterozygous cock-feathered class in which his hen belongs. The 

 change in this male is even more strking than that in the Sebright. 

 The change in the individual feathers is shown in plate 7, figs. 1 and la. 



10. Three types of F 2 hen-feathered castrated males are shown in 

 plate 2, figure 3, and plate 3, figure 3 and figure 4. The first was 

 a dark bird that changed to a lighter red above. The third a gray 

 bird that became bright red ; the second was a light yellow that became 

 deep yellow, etc. The class of hens to which such males belong, as 

 cock-feathered birds, can thus be found out by castration. In this way 

 the F 2 , and back-cross, hen-feathered cocks can be classified with the 

 corresponding F 2 cock-feathered males. 



11. In the F 2 generation, made up of birds from the direct and 

 reciprocal crosses taken together, there were 29 hen-feathered and 

 26 cock-feathered males. In the back-cross (Fi hen by game male) 

 the classes were 2 and 7. The results seem in better accord with 

 the assumption that two factors are present in the Sebright that stand 

 for hen-feathering; that either alone will give hen-feathered birds 

 (intermediate type?) , but that both together give the extreme type of 

 hen-feathering seen in the Sebright. 



12. The difference in color in the two races (Sebright and Black 

 Breasted Game bantams) is very great. The former have almost 

 uniformly laced feathers, while the latter has the varied plumage of 

 the jungle-fowl. The game is strongly dimorphic in color and color- 

 pattern ; the Sebright has the same type of coloration and pattern both 

 in the male and female, but this is deceptive, as castration shows, 

 because the castrated male is as strikingly different from the normal 

 Sebright female as is the cock of other birds from the hen. The 

 resemblance of male and female in this race is due to the suppression 

 of the true male plumage by something produced in the testes. There- 

 fore the heredity of dimorphism resolves itself here into the problem 

 of the heredity of hen-feathering. That the female Sebright has the 

 same genetic factors as the male is shown by the fact that she trans- 



