MENDELISM AND SEX 153 



and striking hypothesis, in support of which he 

 describes a number of interesting facts. 



To put them briefly, the principal points in his 

 theory are these : The male exercises no influence 

 at all in the causation of sex ; this influence is wholly 

 exercised by the female. From various clinical data 

 he arrives at the conclusion that the female produces 

 both male and female ova. This conclusion is 

 interesting, since it is one which is quite Mendelian, 

 but is arrived at by different methods from those 

 employed by the Mendelian, and by one who is 

 not apparently acquainted with Mendelism. But 

 the feature of greatest interest in his theory is his 

 assumption that the right ovary produces male ova 

 and the left ovary female ova. He then further 

 supposes that only one ovary is active and ovulates 

 each month, the other not discharging any eggs. 

 They thus alternately ovulate every other month, so 

 that one month the right ovary is discharging male 

 ova and the next month the left ovary will discharge 

 female ova. 



From these premises he proceeds to show that 

 in normal cases, if we know the sex and date of birth of 

 the first child, the sex of the following children 

 can be predicted for any particular month, and, 

 therefore, a boy or a girl can be begotten at will. 

 The author produces some good evidence in favour 

 of his theory, but it cannot yet be regarded as fully 

 tested. 



He tests his theory by considering the famihes 

 of some eminent people. If ovulation occurs every 



