150 THE LAW OF BIRTHS AND DEATHS 



the sexuality is hastened by outside influences such as 

 checked nutrition." 1 Generally speaking, the degree of 

 asexual fertility seems to be directly proportional to the 

 degree of vitality, and the optimum point for vitality seems 

 to be identical with the optimum point for asexual fertility. 

 The following diagram will give a very clear idea of 

 the relation between the two forms of reproduction : 

 VEEY HIGH NUTRITION. 



HIGH NUTRITION. 



POINT MOST FAVOURABLE 



FOR CONJUGATION on 

 FERTILISATION. 



STARVATION POINT. 



SEXUAL STERILITY. 



THE OPTIMUM POINT FOR 

 SEXUAL FERTILITY. 



SEXUAL STERILITY. 



The centre line represents a scale of nutrition from 

 starvation point up to extremely favourable conditions. 

 Under actual starvation conditions there can, of course, 

 1 Evolution of Sex, chap, xvi. 



