200 GENETICS 



A series of nutrition experiments upon frogs per- 

 formed by Born ('81), Pfluger ('8^2), and Yung ('85) 

 showed that the percentage of female offspring, which 

 normally is slightly over fifty, could be changed to 

 over 90 per cent by regulating the food supplied to 

 the mother before the egg-laying period. Cuenot 

 and King, however, working independently, repeated 

 these experiments with great care, taking into account 

 all the eggs that were laid and not simply the ones 

 that developed, and both obtained negative results. 

 They concluded, therefore, that the high percentage 

 of female tadpoles appearing in the initial experi- 

 ments was due to a greater mortality among the males 

 and not to the transformation of possible males into 

 females. 



There seems to be no doubt that nutrition may 

 affect the percentage of those which reach maturity. 

 If one sex requires a greater amount of nutrition 

 than the other to carry out successfully the more 

 strenuous metabolic changes in its life-cycle, then 

 unequal percentages between the sexes of the sur- 

 vivors resulting- from modified nutrition do not in 

 any way help to solve the problem of determining 

 the sex of the individual. In other words, the elim- 

 ination of one sex through modified nutrition does 

 not "determine" the other sex. 



3. The Statistical Study of Sex 



From statistical sources it has been ascertained 

 that ordinarily there is produced a practical equality 

 in the numbers of the two sexes. 



