446 SOME GENERAL PROBLEMS OF DEVELOPMENT 



Fig. 233. — Twenty-seven different kinds of men. 



Human beings cannot be arbitrarily classified as good, medium, and poor, but such 

 distinctions may be made for purposes of this illustration and the possible combinations 

 tabulated in the manner shown (c/. Fig. 232). (From Walter, Science, June 22, 1923.) 



The Determination of Sex. — The factors that determine sex 

 in man and the famihar animals have been the subject of innumer- 

 able theories since ancient times, all of which now appear to be 

 groundless. Toward the close of the nineteenth century, the 

 hypothesis most widely accepted was that the sex was dependent 

 upon the amount or kind of food the individual happened to receive 

 during development. Experiments in over-feeding and under- 

 feeding of the early stages of vertebrates, such as frog tadpoles, 

 and of insects, such as the caterpillars of moths, gave what appeared 

 to be conclusive evidence. But the repetition of these experiments 

 and other discoveries in recent years have failed to confirm the 

 earher conclusions. It seems that the great proportion of males 

 obtained upon a scanty diet was merely due to the fact that the 

 death rate was higher for the females under this condition, and, 



