712 



THE AMERICAN NATURALIST 



[Vol.L 



which may be omitted here. Another way would be to 

 find many races which differ constantly in regard to the 

 potency of these factors, which conld be shown by the 

 results of cross-breeding. The expectations are, then, 

 that with increasing value of M, in crosses, where these 

 races are used as males in combination with "weak" 

 females, a corresponding type of female intersexuality 

 must appear, giving a complete series from femaleness to 

 maleness. And if we can find a race with so high a 

 potency of M, that the combination lies beyond the 

 epistatic minimum for maleness, then all the would-be 

 females will be transformed into males. I now have at 

 hand such races from Europe and Japan and can pro- 

 duce at will and in 100 per cent, of the offspring all grades 

 between the two sexes. Thus we have one J apanese race, 

 the race G, medium strong in regard to the potency of the 

 factor M. If we cross these males with females of the 

 Japanese race K, which shows comparatively low potency 

 of the female factorial set, all would-be females in I\ 

 are slightly intersexual. We might put them at the point 

 + 15 in our diagram (Fig. 1). Their antennae are 

 feathered, but less than in males, a portion of the wings 

 assumes the brown color of the male, there are not as 

 many eggs as in a normal female, but the mating in- 

 stincts as well as the copulatory organs are still female 

 and the eggs may be normally fertilized. Then there is a 

 European race F and a Japanese race H, both with a 

 still lower potency of the female factorial set. If we 

 cross these with the same Japanese males Gr we get some- 

 what slighter female intersexuality. All secondary sex- 

 characters are more male-like; the instincts are still 

 female and the animals attract the males and mate. Then 

 one of the characteristic hairy egg sponges is laid, but it 

 contains no eggs, only hairs. The copulatory organs are 

 already changed in the direction of the male and no suc- 

 cessful mating and egg deposition is possible, although 

 the abdomen ^is filled with ripe eggs. Then there is 

 another European race F with very low potency of the 

 female factors. If we mate these with the same males Gh 



