274 



THE AMERICAN NATURALIST 



[Vol. XLV 



color and sex determiners in the (jrossuhwiata female 

 and the white female CoUas, both of which are hetero- 

 zygous in these two respects, takes place presumably by 

 quite different methods. Other differences or similarities 

 will doubtless come to light when the white male of Colias 

 is bred. 



The notation which I have here used to express the 

 gametic constitution of Colitis applies equally well to 

 Ainu. ins, assuming tliat inaleness is dominant and that 

 in gametogenesis of the heterozygote for color and sex, 

 viz., the female f/los^ula riata , GL( )X, the male determiner, 

 X, accompanies into one gamete the determiner for high 

 color, G; while the determiner for the undeveloped color, 

 L, is coupled with that for the undeveloped (female) sex, 

 viz., 0. This seems to me to be a more plausible way of 

 expressing the combinations demanded by the results 

 than that there is a "repulsion" between the determiner 

 for femaleness (which is assumed in this view of the case 

 to be dominant) and that for the dominant strong color, 

 G, as suggested by Rateson and Punnett. 



( )n the other hand, it is true that their assumption that 

 in Abnt.ras the male is a homozygous recessive may be 

 applied equally well toColias. However. I am constrained 

 to adopt the view that the male in both is a homozygous 

 dominant for the following reason : 



Dominance in the male postulates the presence in all 

 the sperms and in half the eggs of a chemical substance 

 which in double quantity in an oosperm so stimulates it 

 that the male characters, both primary and secondary, 

 one by one make their appearance; while in single quan- 

 tity (introduced by the sperm only) a lesser stimulus is 

 given, and the organism develops in lesser degree along 

 different lines into the female form. This hypothesis 

 carries within itself an "explanation," feeble though it 

 be, of the male form and color pattern, as well as of 

 those of the female. It is in harmony with the fact that 

 the intenser color of the male butterfly or moth, gener- 

 ally, represents a more advanced condition in the evolu- 

 tion of pigment than the paler colors of the female. 



If, on the other hand, following the interpretation of 



