INHERITANCE OF SEX 265 



it is reached ; just as the image of the end of the 

 passage will be distorted in proportion to the number 

 of mirrors it has to be reflected in on its way to the 

 eye. In the case of the effects produced by the 

 parasites in the crabs and in that of the accessory 

 chromosome, we are, as it were, much farther along 

 the passage, at much closer quarters with the actual 

 constitution of the sexes, and can look directly in. 

 Compare the crabs with the currant moth ; in 

 the former actual sexual changes can be observed; 

 in the latter we could learn nothing about the nature 

 of sex at all if the sex-character had not become 

 entangled in the gamete with a varietal character 

 of pigmentation. Compare the long chain of argu- 

 ment, some of the links of which are not very strong, 

 which leads to the conclusion that a woman produces 

 equal numbers of female- and male -producing ova 

 with the demonstrable fact that in certain insects 

 half the spermatozoa contain an element which the 

 other half lack. 



A comparison between the conclusion based on 

 the Mendelian and cytological evidence in connection 

 with that derived from the crabs is profitable because 

 it may help to divest the problem of certain pre- 

 conceptions which, in my opinion, tend to obscure 

 its real nature. 



The difficulty created by the fact that the Men- 

 delian evidence points to the male as the homozygote 

 and the cytological to the female may be cleared up 

 in one of two ways : It may be proved that the 

 Mendelian indication or (less likely) the cytological 



