98 SEX 



CHAPTER V 



WHAT DETERMINES SEX? 



The determination of sex Different lines of inquiry 

 Possible influence of environment on developing organism 

 Possible importance of the relative condition of the 

 germ-cells at fertilisation Are there predetermined 

 male-producing and female-producing germ -cells? 

 The Mendelian view of sex Possible influence of 

 environment in determining the relative numbers of 

 male-producing and female-producing germ-cells 

 A physiological view. 



THE DETERMINATION OF SEX. From ancient 

 times much interest has been taken in the 

 question : What settles the sex of the off- 

 spring? Many of the answers are bound up 

 with " theories of sex " of an unscientific sort, 

 whose name is legion. There are several 

 scores of books and pamphlets dealing with 

 the problem, most of which must be dis- 

 missed at once because of obviously fatal 

 defects in their scientific procedure. Some 

 lay stress on whimsical conditions, which 

 cannot be seriously considered; others on 

 unverifiable factors, such as the parental 

 desire for a male child. Some are physio- 

 logically absurd ; and others base a big gene- 

 ralisation on an outrageously small number 

 of cases. 



The general problem is : What determines 

 whether a fertilised egg-cell will develop into 

 a male or a female organism? But let us 

 look at a few particular forms of the problem. 

 What are called " true twins " in the human 

 race arise from the division of an ovum into 

 two independently developing cells, and they 



