THE HEREDITY OF SEX 63 



chromatin which by hypothesis determines the 

 male condition, so that here again we have the 

 male condition as something which is distinct from 

 the characteristics of the spermatozoon. But if 

 this is the case, what is the male condition ? The 

 parthenogenetic ovum of the bee is male, and yet 

 it is an ovum capable only of producing s]3ermatozoa. 

 If the single X chromosomes is the cause of the 

 develoj)ment of spermatozoa in the male bee, why 

 does it not produce spermatozoa in the gametes 

 of the female bee, since when reduction takes place 

 all these gametes have a single X chromosome ? 



In biology, as in every other science, we must 

 admit facts even when we cannot explain them. 

 The facts of what we call gravitation are obvious, 

 and any attempt to disregard them would result 

 in disaster, yet no satisfactory explanation of gravita- 

 tion has yet been discovered : many theories have 

 been suggested, but no theory has yet been proved 

 to be true. In the same way it may be necessary 

 to admit that two X chromosomes result in the 

 development of a female, and one X,ov XY chromo- 

 somes result in the development of a male. But 

 Mendelians have omitted to consider what is meant 

 by male and female. The soma with its male and 

 female somatic characters has nothing to do with 

 the question, since somatic sex-differences may be 

 altogether wanting, and moreover, the essential 

 male character, the formation of spermatozoa, is 

 by the Mendelian hypothesis due to descent of the 

 male gametes from the original fertihsed or un- 

 fertilised ovum. The Mendelian theory therefore 

 is that when an ovum has two X sex -chromosomes 

 it can only after a number of cell-divisions, at the 



