130 SEX INHERITANCE 



appeared. The results are in many respects like 

 those of Goldschmidt. 



Sturtevant has studied a race of intersexes in 

 Drosophila simulans. The intersexual individuals 

 are all alike, and have parts that are characteristic 

 of normal individuals of both sexes (ovipositor, 

 seminal receptacle, etc., of female; genital segment, 

 claspers, anal plates, etc., of male). Genetic evi- 

 dence shows that the intersexes are females, in 

 that they have two X-chromosomes, even in the 

 male-appearing parts. The result is produced by 

 a second-chromosome recessive mutant gene. In 

 this case, then, we are dealing with a modification 

 of the development of the female, — not with a 

 disturbance in the usual sex-determining mechanism. 

 In the cases of intersexuality recorded by Gold- 

 schmidt, Harrison, and others there seems to be no 

 proof that there is a single sex-determining gene that 

 has a different ''potency" in different species. The 

 case of Drosophila simulans shows that it is not admis- 

 sible to assume such an explanation without proof. 



Triploid Intersexes in Drosophila 

 Melanogaster 



In Drosophila melanogaster, Bridges has found a 

 strain that continually produces individuals that 

 are intermediates between males and females. These 

 ''intersexes" can always be easily distinguished 

 from normal males or females because of their 

 larger size, their coarse-textured eyes, and by other 



