WHAT DETERMINES SEX? 109 



may be sex-hybrids or heterozygous male 

 D(R) x female D(R) a view supported by 

 Castle; or the male alone may be hetero- 

 zygous, the female being a homozygote 

 recessive male D(R) X female R a view 

 supported by Correns ; or the female only may 

 be heterozygous, the male being a homozygote 

 recessive a view supported by Bateson. 



The last form of the Mendelian interpre- 

 tation is supported by a number of striking 

 facts, especially in regard to the common 

 currant moth and the canary. In the case 

 of the currant moth (Abraxas grossulariata), 

 it is believed that the females are heterozygous 

 (having maleness recessive) and give rise to 

 equal contingents of male-producing and 

 female-producing ova; that the male moths 

 are homozygous as regards sex, being without 

 "the femaleness-f actor/* and give rise only 

 to male-producing spermatozoa; that when 

 a male-producing spermatozoon fertilises a 

 male-producing ovum, the result is of course 

 a male; and that when a male-producing 

 spermatozoon fertilises a female-producing 

 ovum, the result is a female, femaleness being 

 by hypothesis dominant over maleness. If 

 the Mendelian interpretation of sex-inheritance 

 be confirmed, it will probably be found that 

 in some types the male is heterozygous and 

 in others the female. A third possibility is 

 that both sexes are heterozygous or sex 

 hybrids. If the Mendelian view be confirmed 

 it means that maleness and femaleness behave 

 in inheritance like shortness and tallness in 

 dwarf and giant varieties of pea; it implies 

 that there is some definite body perhaps of 



