riddle: control of sex ratio 337 



state which better corresponds to a condition favorable to in- 

 creased storage.* 



The results of these analyses (as well as the calorimetric deter- 

 minations to be mentioned later) have an important relation 

 to the question of a modified or differential maturation, by 

 which the changed ratios might be explained. Bearing on this 

 point we may here make the following observations: It has 

 been seen that the sex actually realized corresponds in fact to 

 levels or grades of metabolism; and we now note that the (stor- 

 age) metabolism which was measured was complete before the 

 beginning of maturation, so that if such a differential maturation 

 should occur it must be looked upon not as a cause but rather 

 as a result of the establishment of that grade of metabolism which 

 does here, and under all of the several known conditions, in the 

 clearest way accompany and correlate with each particular 

 sex. 



But, any assumption of a differential maturation, even 'as a 

 result of or response to these impressed levels of metabolism, 

 brings with it more difficulites than it clears up. Among these 

 it brings the paradox of a rigid selection in favor of the male- 

 producing chromosome-complex in the maturations of the 

 spring, and an equally rigid selection against this same complex 

 in the autumn. Again, it is easily shown by simple breeding 

 tests that such differential maturation does not occur in the 

 spring at least when the female is mated to her own or a closely 

 related species; so that a further assumption would have to be 

 made to the effect that it is the prospective fertilization by a 

 sperm from a wider cross that determines the course of matura- 

 tion! Furthermore, our data on the sex-behavior of series of 

 females from such a wide (generic) cross show that if the male- 

 producing complex was indeed eliminated from the eggs that 

 gave rise to one-half of these females (produced under overwork) 

 these same chromosomes cannot be the real or sole cause of 



8 For example, Overton found that withdrawal of water from the cells of 

 Spirogyra was followed by an increased storage or accumulation of starch, etc. 

 Embryonic tissues generally have high water content and show most rapid di- 

 vision, differentiation and growth (not storage), etc. 



