IX] HEREDITY AND SEX 131 



develop. But it should be pointed out that environ- 

 ment may influence the proportion of male-producing 

 and female-producing germ-cells which come to 

 maturity, and a considerable amount of evidence has 

 been collected showing that the varying proportions 

 of the sexes under different conditions may be due to 

 this cause. If some conditions favour the output of 

 male-producing eggs, others of female-producing, the 

 conditions will then indirectly affect the sex of the 

 offspring, not by changing it in the individual, but by 

 causing more individuals of one or the other sex to 

 be born. 



One of the reasons which have led biologists to 

 assume that environment may modify the sex of the 

 individual is the fact that changed conditions may 

 influence the extent to which the sexual characters 

 develop. Worker bees for example are females in 

 which modified food and surroundings have prevented 

 the full development of the female characters. The 

 characters proper to one sex frequently are found 

 in a rudimentary condition in the other, and in 

 abnormal cases may develop. Or these characters may 

 be prevented from developing in the sex which nor- 

 mally exhibits them by certain conditions, especially 

 by removing the ovary or testis from the young 

 animal, for example the non-appearance of horns in 

 castrated deer or the disappearance of the distinctive 

 sex-features in Crabs in which the reproductive organs 



9—2 



