500 



HEREDITY AIVD SEX 



London, 1901), much importance was attached to the supposed 

 influence of nutritive and other environmental conditions, 

 operative on the parents, on the germ-cells, or even on the early 

 stages of the developing organism where there is evidence of 

 prolonged sexual indifference or neutrality. In some cases it 

 still seems legitimate to believe that external conditions may 

 have a role in sex-determination, but in many cases further 

 experiment has invalidated results previously accepted. 



Fig. 47. — Diagram of protoplasmic changes : B, in plan. A, in elevation 

 The anabolic or constructive processes are represented to the left ; 

 the katabolic or disruptive processes to the right. 



More and more it seems being proved that the sex is fixed in 

 the fertilised ovum or earlier, and it is difficult to verify any 

 hypothesis as to the conditions of determination at this early 

 stage. 



In some cases there are demonstrably two kinds of ova, 

 and in some cases the two kinds develop into different sexes. 

 This suggests predetermination of sex on the part of the ovum. 

 But we do not know why there should be two kinds of ova. 



