108 SEX INHERITANCE 



is produced in the testes of the hen-feathered birds, 

 that, acting together with the somatic complex of 

 the same bird, inhibits the full cock-feathering. It 

 seems probable that an internal secretion is set 

 free from the testes that acting in conjunction with 

 substances produced in the feather follicles, causes 

 the feathers to be like those of the hen, while in the 

 absence of this secretion the follicles produce cock- 

 feathering. In this case, one of the intermediate 

 stages between the gene and the feather is located 

 in the testes. It is interesting to note in this con- 

 nection that when a hen has her ovary removed 

 she also becomes cock-feathered (Goodale). In the 

 ovary there are certain cells, called luteal cells, 

 that are supposed to produce an internal secretion. 

 In the adult of ordinary cocks these cells are absent, 

 or rare, while in the testes of the Sebright, and also 

 in the testes of another race of hen-feathered birds, 

 the Campines, cells are present that look exactly 

 like those of the female ovary. It seems plausible 

 at least, that the secretion in question is produced 

 by these cells and that it produces the same effect 

 on the hen and on the hen-feathered male. In the 

 Campines the hen-feathered males are recognized 

 in some countries as the standard, while in other 

 countries cock-feathered males are the standard. 

 Here also it appears, although the evidence is less 

 certain, that the tw^o races differ by a factor 

 for hen-feathering, and here too castration of the 

 hen-feathered cockerel causes him to develop the 

 cock-feathering like that of the other race. 



