RELATING TO SECONDARY SEXUAL CHARACTERS. 83 



his race without restraint. The facts in the case are that the plumage 

 of the male is the direct result of his genetic composition; the female 

 has the same genetic composition (the sex-linked characters are duplex), 

 but the ovary produces a substance that holds them in restraint. Put 

 in this way, there is nothing further to be explained, unless we insist 

 on finding an explanation as to how the species came to have its 

 genetic constitution. In other words, if we are not satisfied with the 

 statement as to the actual situation, we must explain it by a utili- 

 tarian appeal to a relation between the plumage and the world outside 

 of the individual or the species. To those who feel unsatisfied to leave 

 the case as it stands on a physiological basis, there is another hypo- 

 thetical means of escape. It may be assumed that the genetic factors 

 that are instrumental in producing the secondary sexual characters 

 have also other but unknown influences in the economy of the species, 

 color and ornamentation being by-products of these factors whose 

 utility in other directions accounts for their presence. Such a philos- 

 ophy has perhaps one redeeming feature, since it suggests the possibil- 

 ity of searching for other influences influences that only incidentally 

 give the striking coloration and ornamentation of the males. 



At first sight the absence of cock-feathering in the Sebright may 

 seem to furnish the occasion for such a quest. It might appear that 

 since only one or two genetic factor differences are responsible for the 

 "nuptial" plumage of the male, that this plumage may have originated 

 in one or two genetic changes. Such an argument is fallacious, how- 

 ever, for very many genetic factors may historically have been neces- 

 sary to build up the nuptial plumage of the male. The breeding 

 experiment shows no more than that one or two other factors have 

 appeared that counteract the effect of all that the others are capable of 

 producing; the experiment throws no light upon how many or how 

 few these other factors may be. That the nuptial complex is still 

 present in the Sebright is evident after castration. Castration shows 

 only that the testes in the Sebright produce some material that keeps 

 down the effects of all the other factors combined. This conclusion, 

 it is true, somewhat simplifies the problem for those who appeal to 

 natural selection as suppressing in the female the feathering of the 

 cock, because it shows that this could have been accomplished by one 

 or two Mendelian factors that appeared of such a kind that they caused 

 the ovary to produce a substance antagonistic to the influences coming 

 from the genetic complex of the species. 



With this by way of provisional exposition, let us return to the ques- 

 tion as to whether the Sebright-game cross throws any other light on 

 the possibly useful character of the genetic factor or factors that 

 produce cock-feathering. It is obvious that the evidence gives us no 

 clue at all, for with the exception of the normal allelomorphs of the 

 dominant factor for hen-feathering, all the other factors are still 



