No. 609] 



THE THEORY OF THE GENE 



539 



It does not seem to me to lessen in any way the im- 

 portance of embryology to keep its problems for the pres- 

 ent separated from those of the method of transmission 

 of hereditary characters. It may well be that there are 

 more important discoveries to be made in future in the 

 field of embryology than in genetics, and that when the 

 subject of chemical embryology has arrived at its goal it 

 may be worth while to combine the two subjects into 

 a single one. I am also aware that to many persons the 

 interest in genetics is greatly increased when certain 

 stages can be demonstrated through which the genes bring 

 about their results. Far from being in opposition to such 

 interests, I can illustrate this very point by a case of my 

 own. The cock bird of the Sebright bantam is "hen- 

 feathered" (Fig. 3a), i. e., certain of the secondary sexual 

 characters are like those of the hen (Fig. 3&). This is 

 most noticeable in the short neck, back and saddle feathers 

 as well as in the absence of the long tail feathers. When 

 these birds are crossed to game bantams (a race in which 

 the male has the usual secondary sexual characters, Fig. 

 4), the Fi cocks are hen-feathered (Fig. 5a). This is true 

 both when Sebright is crossed to game $ and when game 



is crossed to Sebright $. The latter cross shows that the 

 dominant character is carried by the female Sebright as 

 well as by the male. 



AVlien these F^ birds are inbred, they produce in the 

 next generation (Fg) both cock-feathered and hen-feath- 

 ered males. There is complete segregation of the types 

 that went into the cross. Wliether one or two genes for 

 hen-feathering are present is not entirely certain, but that 

 Mendelian segregation occurs there can be no doubt. 



I was led to see what would happen when the hen- 

 feathered birds were castrated. Goodale had shown that 

 when the hen of normal breeds is spayed, she develops 

 the full male plumage, including the special feather re- 

 gions in which the Sebright is hen-feathered. At the 

 time of castration a few feathers were removed. The 

 new ones that came in showed at once that a great change 



