44 



DAVID D. WHITNEY. 



in which various protozoa and rotifers were living. They were 

 left in this filtered water for about 12 hours, during the night, 

 without food. During this time each female laid 3-4 eggs and 

 the next morning the old females were taken out, Polytoma food 

 was added, and the eggs allowed to hatch. Several hours later 

 the young females that hatched from these eggs were isolated in 

 separate watch glasses and fed Polytoma and a species of a small 

 Euglena. 



In Table III. this same fact is shown again to be true for the 

 English species. However, this is a relatively minor point and 



TABLE III. 



SHOWING THAT WHEN THE ENGLISH STRAIN WAS SUBJECTED TO A UNIFORM AND 

 CONSTANT DIET OF THE COLORLESS PROTOZOA, Polytoma, ONLY FEMALE- 

 PRODUCING FEMALES WERE PRODUCED BUT THAT WHEN IT WAS 

 SUBJECTED TO A SUDDEN CHANGE OF DIET FROM THE 

 Polytoma TO A GREEN PROTOZOA, Chlamydomonas, 

 AS HIGH AS 85 PER CENT. OF MALE-PRODUCING 

 FEMALES WAS PRODUCED. 



Experiments During January and February 1015 on an English Strain of Hydatina 



senta. 



may only be of importance to any one wishing to obtain cyto- 

 logical material. 



If Table III. is compared further with Table II. it is evident 

 that they are very similar in all points with the exception that 



