No. 535] 



NOTES AND LITERATURE 



429 



size is also different, the female egg being larger. But the size- 

 difference is not all-important, either, for the winter egg of the 

 rotifers or daphnids i.s still larger, yet undergoes complete reduc- 

 tion, but will not develop in this condition unless fertilized: then 

 it produces a female, being in the fully duplex, 2N condition. 

 Sex in such cases i.s correlated with a particular cell-constitu- 

 tion, but this cell-constitution may be influenced by the environ- 

 ment ; hence the environment may i ml in i ll // control sex. 



Boveri's present contribution adds another important case to 

 those previously on record. In the nematode, too. protoplasmic 

 conditions control sex, but it is quite possible that external 

 agencies as yet not identified may in this case also determine 

 those protoplasmic conditions and so indirectly determine sex. 



The question naturally arises whether the same may not be 

 true in the higher animals also, those which are sexually sepa- 

 rate. This idea has been strongly advocated from time imme- 

 morial, and still has its adherents, hut a really critical analysis of 

 the evidence shows that it rests on a very insufficient basis. In 



differentiates male-producing from fe 



