Edith E. Hodgkinson 191 



It is to be noted that the arrhenotokous females persisted through 

 4 generations when the rotifers were transferred to the horse manure 

 solution, after which none were produced. 



Experiment III. A thelytokous female was put in green protozoa 

 culture ; after laying a certain number of eggs it was transferred to 

 concentrated horse manure solution in which the remainder of the eggs 

 of that generation were laid. This was repeated through two more 

 generations, the parent in each case being a rotifer that had hatched 

 out in the green protozoa culture. The table gives the results 



Green protozoa culture T Horse manure solution 



TAAAAAATTT yrrrrrrrrrTrrrrrTTrrrrr 



J 



AAAAAAATT yrrrrrrrjTrrrTT 



\ 



TTTAAATTTATATT j<xTTTTTTTTTTTTTT 



A definite change occurred in the same generation : whilst the 

 parent was in the green protozoa culture numerous eggs were laid 

 which hatched out into arrhenotokous females, but after transfer to the 

 horse manure solution no arrhenotokous females were produced. This 

 change occurred in each generation. 



Expenment IV. A rotifer and its descendants were put in a culture 

 of green protozoa kept diluted with spring water so that it was com- 

 paratively poor in protozoa. The results were 



Further experiments are needed here to show if a decrease in the 

 food supply and in the assimilation of the green protozoa affects the 

 output of males. 



Experiment V. Four rotifers were isolated and put in green pro- 

 tozoa culture. They were kept in sunlight during the day and in 

 electric light duHng the night so that assimilation b}^ the green protozoa 

 was continuous. The results were 



