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THE AMERICAN NATURALIST [Vol. XL V 



?c? Female ? 



^ Male <? c? 



In certain groups of animals, as in Abraxas amongst 

 insects, and in poultry amongst birds, the first scheme is 

 essential to an interpretation of the facts obtained by 

 experiment. In other groups, as in Drosophila amongst 

 insects, and in man amongst the vertebrates, the second 

 scheme accounts for the experimental results. 



These methods of formulation are open to two serious 

 objections. As the tables show, the combination of 2 S 

 stands for the female in one case, and for the male in the 

 other. In order to avoid this apparent contradiction it 

 is assumed that in some groups femaleness dominates 

 maleness, and in other groups maleness dominates fe- 

 maleness, which seems to me paradoxical at least. 



It will be observed also that in the first of these 

 schemes the male carries none of the sexual characters 

 of the female, and in the second scheme the female car- 

 ries none of those of the male; both of which assump- 

 tions do not seem to me to be completely in accord with 

 fact. Cytologists represent these same two schemes in 

 a different way. They represent in the one case the 

 female character by X; and the male by the absence of 

 X. Thus: 



Gametea 



This representation covers the first class of cases 

 where the female is heterozygous. For the second class, 

 where the female is homozygous, the following scheme is 



