452 



Thos. H. Montgomery, Jr. 



than the number that mate, seeing that many may be killed by 

 direct competition. More generally the male lives a simpler life 

 than the female, is less active both physically and psychically, 

 less fit for the struggle for existence, such as is the male in the spi- 

 ders we have been considering; in such cases many males die 

 before reaching maturity, and for such species the male ratio would 

 be high. Then where eggs do not require fertilization, as in par- 

 thenogenetic generations, selection would remove the males. 



Thus the average male ratio of a particular species would be 

 fixed primarily by selection and segregation: these factors would 

 confine in rather narrow bounds the ratio of that particular species. 

 They would keep the number of males rightly proportioned to 

 the number of ova that are to be fertilized, without unnecessary 

 waste of either. 



And since the factor of chance and the factor of Mendelian 

 inheritance cannot explain certain specific sex ratios, it is at least 

 suggested that these factors may also fail to determine sex within 

 the offspring unit.^^ 



'* It may have some statistical value to append a count of 8796 adult individuals of the Rose 

 chafer, Macrodactylus subspinosus, that I made during June, 1901, on individuals collected from 

 one small garden near West Chester, Pa., and which gives a male ratio of 1.31: 



