234 HEREDITY AND SEX 



zoologists, physicians, and laymen alike perpetually 

 discovering some new relation between food and sex? 

 It is hard to say. Only recently an ItaUan zoologist, 

 Russo, put forward the view that by feeding animals 

 on lecithin more females were produced. He claimed 

 that he could actually detect the two kinds of eggs 

 in the ovary — the female- and the male-producing. It 

 has been shown that his data were selected and not 

 complete ; that repetition of his experiments gave no 

 confirmative results, and probably that one of the two 

 kinds of eggs that he distinguished were eggs about to 

 degenerate and become absorbed. 



But the food theories will go on for many years to 

 come — as long as credulity lasts. 



Temperature also has been appealed to as a sex fac- 

 tor in one sense or another. R. Hertwig concluded 

 that a lower temperature at the time of fertilization 

 gave more male frogs, but Miss King's observations 

 failed to confirm this. There is the earher work of 

 Maupas on hydatina and the more recent work of 

 von Malsen on Dinophilus apatris. I have already 

 pointed out that Maupas' results have not been con- 

 firmed by any of his successors. Even if they had been 

 confirmed they would only have shown that tempera- 

 ture might have an effect in bringing parthenogenesis 

 to an end and instituting sexual reproduction in its 

 stead. In hydatina the sexual female and the male 

 producing individual are one and the same. A more 

 striking case could not be found to show that the en- 

 vironment does not determine sex but may at least 

 change one method of reproduction into another. 



There remain von Malsen' s results for dinophilus. 



