192 Experiments on the Rotifer Hydatina 



The results are too scanty to prove that increased assimilation by 

 the green protozoa causes a rise in the proportion of arrhenotokous 

 females. This is however not unlikely in view of the fact that Shull 

 and Ladoff ^ have found that increased oxygenation leads to the output 

 of a higher proportion of arrhenotokous $ $ . 



The results recorded in this paper serve to confirm the conclusions 

 of other observers as to the alteration in the proportion of arrheno- 

 tokous females brought about by a change of diet from protozoa without 

 chlorophyll to protozoa which contain this substance. Both Whitney 

 and Shull have attempted to push the analysis further and to bring 

 about the alteration in the relative proportions of the two kinds of 

 females by means of substances of more simple constitution chemically. 

 Their attempts have shewn that a wide field of inquiry is still open 

 here, and I do not feel that at present I can add anything to the full 

 and suggestive discussions which are to be found in their papers. 



1 Journ. Exp. Zool. 1916. 



