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DAVID DAY WHITNEY 



periments were attempted but proving too tedious because of 

 various difficulties in the technique of feeding and isolation they 

 were abandoned and mass cultures were reared in four liter bat- 

 tery jars. These jars were placed in a large pan of running 

 water in a south window and soon various kinds of protozoa 

 developed in them. Small quantities of Chlamydomonas were 

 added occasionally until the jars were well balanced and several 

 thousand of the rotifers had developed. At this period nearly 

 all of the females were carrying female eggs. Considerable 



Diagram 2 Brachionus bakeri. Experiment 1 of table 2. Showing the pro- 

 duction of a high percentage of male-producing females when the food condi- 

 tions were changed by the additions of considerable quantities of the green 

 flagellate, Chlamydomonas. C indicates the addition of the Chlamydomonas. 



quantities of Chlamydomonas were then added to the jars and 

 soon the number of females carrying female eggs decreased and 

 the number of females carrying male eggs increased. In one 

 jar which contained many thousand females it was estimated 

 that only about 10 per cent were carrying female eggs and about 

 90 per cent were carrying male eggs. The details of these ex- 

 periments are shown in table 2, a plotting of experiment 1 is 

 shown in diagram 2, and drawings showing the females with the 

 different eggs attached and also of a male are shown in figure 2. 



