222 Basis of Sex Determination 



correspondingly decreasing. . . . Hand in hand with this 

 the abdomen increases in size, reaching in the most extreme 

 cases two-thirds of the female size (without containing 

 eggs). The same is true for the instincts which become 

 more and more female. 



(And also for the copulatory organs which also become 

 more and more female.) 



As stated above, the main fact that every desired 

 degree of intersexualism can be produced at will by 

 properly combining the races for breeding, and the 

 intersexual potencies of the different races has been 

 worked out by Goldschmidt. ' 



6. The relation between chemical substances cir- 

 culating in the body — either derivatives of food taken 

 up from without or of chemical compounds formed 

 naturally inside the body — and the production of 

 sexual characters is best shown in the polymorphism 

 found among the social ants, bees, and wasps. Here we 

 have, as a rule, in addition to the two sexes a third 

 one, the workers, which are in reality rudimentary 

 and for that reason sterile females. They differ more or 

 less markedly from both the typical male and female 

 in their external form, and, as a rule cannot copulate 

 owing to their deficient structure. This third sex, 

 the sterile neuters, can be transformed at desire into 

 sexual females in certain species, as P. Marchal has 

 demonstrated. He worked with a form of social wasps 



^ Goldschmidt, R., Proc. Nat. Acad. Sc, 1916, ii.,'53; Ztschr, induct. 

 Abstamtnungslehre, 19 12, vii., and 19 14, xi. 



