MENDELIAN HEREDITY 269 



Now, the indications that one sex, to state it in 

 the broadest terms, is bipotential and the other 

 unipotential is based on minute evidence of a strictly 

 a "posteriori nature, whilst the conclusion that both 

 sexes are bipotential is based on evidence which its 

 author claims to be " massive," and reached by the 

 a priori ladder, which he believes to be trustworthy. 

 For my own part, the minute weighs more heavily 

 with me than the massive. At any rate, I propose 

 to regard it as more probable that one sex is 

 bipotential and the other unipotential than that both 

 are bipotential. And in any case, this is a secondary 

 point at issue. The essential one is : Which came 

 first, the Mendelian or sexual mode of inheritance ? 

 And by the sexual mode I mean, now, the theory 

 that one sex is bipotential and the other unipotential, 

 and not Dr. Reid's alternative latency and potency. 

 The Mendelian may here interpose that I am holding 

 his brief. I am, in the sense that I am prepared to 

 accept an interpretation of sex on the basis of the 

 Mendelian one. But I also incline to the view that the 

 sexual preceded the Mendelian mode in so far as it 

 seems to me likely that the mode of inheritance from 

 which both are differentiations was, in the first place, 

 only used (if the expression may be allowed) by 

 sexual characters, and was of the type DR, x RR, 

 or, more generally, heterozygote x homozygote, 

 or xy X XX ; and that all the phenomena which we 

 regard as characteristically Mendehan — the existence 

 of pure dominants and recessives, the uniformity of 

 first hybrid generations, the segregation in the ratio 



