5*2 



THE AMERICAN NATURALIST [Vol. XLVIII 



is self evident; for, in demonstrating that all of the 

 gametes of variolarius earn/ spot the authors actually 

 destroy their own argument. 



It only remains to point out some of the different ways 

 in which a factor being present in duplex both in the male 

 and in the female produces its effect only in the male. In 

 some cases it has been shown that the ovary produces 

 some substance that is inimical to the production of cer- 

 tain characters. For instance in fowls and in ducks the 

 presence of the ovary suppresses the development of 

 the male plumage. That the factors for the male plumage 

 are present is shown by its development when the ovary 

 is removed. But in some insects it has been found that 

 neither the ovary nor the testis produces these kinds of 

 substances; for, when the testis or the ovary is removed 

 the secondary sexual chaiacters are not affected. Here 

 the mode of explanation must be different. But the con- 

 ditions, or complex, or factors that produce the ovary in 

 the female are acting in every cell of the body, and con- 

 sequently an effect, that is indirectly caused in the fowl 

 or duck, might be directly caused in the insect. For, each 

 cell is a chemical factory. Such a factory may help to 

 produce an ovary and the ovary produce a substance that 

 demonstrably suppresses the male plumage, or the same 

 kind of factory may do similar work through the activity 

 of some other part of the body, or conceivably it may do 

 its work in every cell of the body. This it seems to me is 

 the most reasonable view to take of the matter in the case 

 of the variolarvus-servus cross. We can express the same 

 thought in symbols by representing:- the female of vario- 

 larius by XXAABBCCDDSS, etc., and the male by 

 XYAABBCCDDSS, etc. The chemical interaction be- 

 tween two X's and the rest of the cell is of such kind that 

 it produces a female, and the female complex, as such, is 



