riddle: control of sex ratio 351 



torial basis of the phenomena has hitherto been used in the 

 discussion of these results; but recently Goldschmidt ('16) has 

 stated that "very important new facts will be published later 

 which will probably enable us to replace the symbolistic Men- 

 delian language, used here, by more definite physico-chemical 

 conceptions." Such newer descriptions — we would say — is 

 wholly in line with the requirements of present data on sex. 

 In Whitman's and our own material it has been clear from the 

 first that the results far overstep the possibility of treating 

 them in Mendelian terms, for it has been apparent from the 

 beginning that we have had to do not with three or four points 

 merely, but with a flowing graduated line. In the work with the 

 moths, however, sex is clearly described in quantitative terms, 

 and it seems fairly certain that when the functional basis of sex 

 shall have been identified it will be found that sex accords 

 with metabolic grades there, as it does elsewhere. 



It is clear then that all of the animal-forms for which there is 

 reasonable evidence of sex-control show important correspon- 

 dences with the situation fully elucidated in the pigeons. And 

 that where the sex-differentials known to exist in the pigeon's 

 ova have been traced in adults of the two sexes, the parallel 

 rigorously holds there also. A general classification of male and 

 female adult animals on the basis of a higher metabolism for the 

 one and a lower for the other, was indeed made by Geddes and 

 Thomson ('90) many years ago. It now seems beyond ques- 

 tion that this conclusion of these authors is a correct and impor- 

 tant one. 



It remains to point out that another very old and much 

 worked line of investigation supplies further confirmatory evi- 

 dence for our present point of view. Studies on the effects of 

 castration, gonad-transplantation, and gonad-extract injection, 

 constitute a large body of observations which deal with sexual 

 phenomena associated with the internal secretions of the sex- 

 glands. These internal secretions, let it be remembered, are 

 themselves metabolites, which have the capacity to influence the 

 metabolism of some, many, or of all the tissues with which they 



