ENDOMIXIS IN PARAMECIUM AURELIA. 



443 



These experiments were carried on from October 15, 1914, 

 to March 10, 1915; a period of 145 days. The subcultures 

 employed were A, AE, and O throughout the work and B from 

 its isolation on January 8, 1915, to the end. Each of these 

 subcultures represents a different race of Paramecium aurelia, 

 except A and AE, both of which were originally derived from 

 the same stock, Main Culture I., about 1,000 generations before. 



FIG. 3. 



All of these subcultures were subjected to a varied culture medium 

 and to the ordinary fluctuation in room temperature. 



Sister subcultures (designated At, AEt, Ot and Bt], were 

 isolated line by line from the above cultures at the start of the 

 experiment and were subjected to a constant culture medium 

 of beef extract. The temperature was maintained relatively 

 constant at about 26 C. in a thermostat. 



A. 



Study of the periodicity of rhythms and endomixis in different 

 races of Paramecium aurelia when bred under the same varied 

 culture conditions. 



Fig. i presents the graphs of the division rate of subcultures 

 A, AE, and B throughout this experiment. A study of the 



