ONTOGENESIS 235 



this objection as Bateson has suggested. Thus, 

 it might be the female that is the hybrid with 

 femaleness dominant. Though by this assump- 

 tion we are relieved of the dilemma into which we 

 were thrown by the peculiarity of the bee's eggs, 

 we fall into a new one, because of the observa- 

 tions by Henking and Wilson that there are 

 morphologically different spermatozoa that de- 

 termine the sex of many kinds of insects, and 

 because of the difficulty of explaining many of 

 the circumstances attending parthenogenesis. 



A very ingenious solution of the difficulty of 

 avoiding entanglements in endeavoring to ex- 

 plain sex along Mendelian lines has been thought 

 out by L. Doncaster, who suggests that the 

 Mendelian pairs are not male and female, but are 

 male and no sex and female and no sex. The 

 male is pure, but produces spermatozoa of two 

 kinds, viz., those with sex determinants and those 

 without them. The female is a sex hybrid pro- 

 ducing both male and female eggs in equal num- 

 bers. He assumes that there is selective fertiliza- 

 tion by which female eggs fertilized by male 

 spermatozoa give rise to females and male eggs 

 fertilized by no sex spermatozoa give rise to 

 males. 



In accounting for the conditions of partheno- 

 genesis, it is assumed that females are of two 

 kinds as the result of fertilization by different 

 kinds of spermatozoa, and that their maturation 

 processes differ so that they may give rise to 

 either males or females. These views accord with 

 certain observations made by Doncaster upon the 

 maturation phenomena of insects. 

 From these brief outlines of the theoretical aspects of 

 the problem, it will appear that the matter of sex deter- 

 mination is by no means clear, and that there are diffi- 

 culties in the way of solving it. 



