718 



THE AMERICAN NATURALIST 



[Vol. L 



Weak race ? = [FFj Mm c?= [ff] MM. 



80 50 80 50 50 



The F, cros! 

 would give: 



of these, using the strong race as mother, 



Fj ? [ff] 

 100 



Aim 



50 



: normal female, 



Fj c? [FF| 



MM 



: intersexual male, as e = — 10. 



100 60 50 



Every single male ought to be intersexual. Through the 

 kindness of Dr. Machida in Tokyo, who first has reached 

 this strange result, I could bring back from Japan two 

 such races and they breed exactly according to ex- 

 pectation. 



This is about the skeleton of our work around which 

 of course many interesting experimental, morphological, 

 embryological, cytological and physiological facts are 

 grouped. I am rather optimistic in regard to the general 

 conclusions, which might be drawn from these facts as 

 well as regards the sex-problem as on some fundamental 

 questions of heredity. Combining these facts with the 

 work on hormone action as related to sex we can, I think, 

 form a pretty clear idea about sex-differentiation and 

 determination. 9 



If we put them in line with the facts of experimental 

 embryology concerning the determination problem we 

 see the outlines of a promising theory of heredity. But 

 this can be discussed only when a full account of the work 



