INTERNAL CONDITIONS 495 



ment would depend on the relative prepotency of the two 

 gametes. In the case of hermaphrodite animals, one kind of 

 e.g'g and one kind of sperm would suffice. 



This solution savours a little of Columbus and the %gg, but 

 it is not to be hastily brushed aside. It is easy to say that it 

 simply shunts the difficulty a little further back, for what are 

 the conditions producing two kinds of eggs ? But ij the primary 

 difference between male and female, between a sperm-producer 

 and an egg-producer, is merely a slight physiological difference 

 in the gearing of the metabolism, ij tL;; contrast between male 

 and female is like the contrast between sperm and ovum con- 

 sidered as cells, ij the antithesis is simply a particular expression of 

 omnipresent fluctuation in the ratio of anabolism to katabolism, 

 then we do not see that the assumption of two kinds of ova and 

 two kinds of spermatozoa is a mere begging of the question. 



Where there is complex dimorphism between the sexes, it is 

 necessary to make the further assumption that all the gametes, 

 whether maternal or paternal, and whether disposed towards 

 female-production or towards male-production, have a complete 

 set of the hereditary characters of the two sexes (so far as these 

 require the postulate of germinal representation), and that the 

 physiological difference of protoplasmic "gearing" determines 

 which set is to find expression and which set is to remain 

 latent. 



The drawback to the theory is that it remains a hypothesis, 

 except in so far as there are known cases of demonstrable 

 differences between two kinds of ova or between two kinds of 

 spermatozoa. 



In his recent theory of sex-determination. Dr. John Beard 

 assumes two kind of eggs and two kinds of spermatozoa, but 

 he does not credit the spermatozoa with any share in deciding 

 the sex. Indeed, one kind of spermatozoon — the "female" 

 spermatozoon — has not even fertilising power. A " female " egg 

 develops into a female, and a " male " egg into a male. The 



