THE THEORY OF SEX 605 



VI 



Starting from the foregoing facts, we might consider the 

 theory of the sex-enzymes to be proved, in general, as com- 

 pletely as possible. But, if we try to work it out in detail, some 

 difficulties appear which have to be overcome by further experi- 

 mental work. The difficulty comes in at the following point. 

 The quantitative relation of the andrase and the gynase is, in 

 our case, such that the amount of the gynase is constant for l^oth 

 sexes, whereas the andrase is twice as concentrated in the male 

 as in the female. If, now, in normal sexuality, the action of the 

 andrase in the female falls after the end of differentiation — 

 which, in the moth, practically coincides with hatching — the 

 action of the gynase in the male ought to be so early that every 

 male ought to be intersexual. This difficulty might be over- 

 come by assuming an inactivating or retarding effect of one 

 enzjane on the other. But this assumption would lead to new 

 difficulties in the case of intersexuality, besides being in the 

 nature of a loop-hole. Another way would be to ascribe to the 

 sex-enzymes the properties of autocatalysers, which, however, 

 also fails to work out satisfactorily in detail. A better solu- 

 tion is suggested by the following facts. In the gypsy-moth, 

 as in many other insects, the male develops, under identical 

 cultural conditions, considerably faster than the female, the dif- 

 ference being very regular in healthy cultures. This fact is 

 known to every breeder because of its rather unfortunate influ- 

 ence upon experimental breeding, since the males are often gone 

 by the time the females, to which they were to be mated, ap- 

 pear. We must suppose that this differentiating effect upon 

 growth and metabolism is also one of the properties of the two 

 enzymes. It is, furthermore, a fact that the same rule ap- 

 plies to intersexuality. We long ago observed that on an aver- 

 age intersexual females grow faster than normal females, and 

 intersexual males more slowly than normal males. It becomes 

 especially clear when, in a culture yielding nothing but males, a 

 single female appears, or an occasional normal male in a culture 

 yielding nothing but intersexual males. (The explanation for 



