MENDELISM AND SEX 201 



the male be homozygous in the ordinary forms of insects, 

 what sense can be found in the production of two forms 

 of spermatozoa? Still worse is the dilemma presented by 

 the parthenogenesis of the bee or ant. If we here assume 

 that the egg eliminates the female tendency in maturation, 

 fertilisation should produce a homozygous male, which is 

 contrary to fact. If, on the other hand, we assume the male 

 tendency to be eliminated, parthenogenesis should produce 

 females, which is also contrary to fact. The only escape from 

 this seems to lie in the assumption that if unfertilised the 

 egg eliminates the female tendency ; if fertilised, the male. 1 

 But can we regard this as probable ? " 2 



Since writing the above Professor Wilson's views have 

 been modified, and he now agrees that, as is pointed out 

 by Castle, 3 his method of quantitative formulation is 

 quite as open to a Mendelian interpretation as the other 

 view. The essence of his present view is, " that one sex 

 is cytologically a ' heterozygote,' the other a ' homozygote,' " 

 the latter being sometimes one sex and sometimes the other, 

 exactly as Bateson assumes from experimental results. 

 Male and female " tendencies " are not conceived (as for 

 instance Correns seems to conceive them) as two distinct 

 and opposing things, but as differing primarily by a quanti- 

 tative relation i.e. in respect to the X element. This 

 avoids many difficulties, particularly in parthenogenesis, 

 and gets rid of selective fertilisation. This is essentially 

 in agreement with Castle's new view, and wholly different 

 from his early one which involved selective fertilisation. 4 



It will be seen later that the interpretation adopted by 

 Professor Wilson ^is in many ways similar to that advocated 

 in these pages. Sex being an alternative character, neces- 

 sarily resembles the Mendelian characters in being alter- 



1 This suggestion is due to Professor Morgan. 



2 Wilson, E. B., " Recent Researches on the Determination and Heredity of 

 Sex," Science, N.S., vol. xxix., 1909. 



3 Science, March 5, 1909. 



4 Letter from E. B. Wilson to Author, April 22, 1910. 



