ENDOMIXIS IN PARAMECIUM AURELIA. 



457 



time in days between successive reorganizations is 20 and 35 in 

 B, and 25 and 30 in Bs. Therefore in both cultures the same 

 number of days (55) elapsed from one endomixis to its second 

 following occurrence. On the other hand in B the process was 

 in progress at the 335th, 37oth and 435th generations, that is at 

 intervals of 35 and 65 generations, while in Bs it took place at the 

 335th (when Bs was isolated from B}, 36oth and 38oth genera- 



B< 





FIG. ii. 



tions, or at intervals of 25 and 20 generations. Therefore in 

 B 100 generations were attained from one endomictic period to 

 the second following occurrence of the process; while in Bs only 

 45 generations occurred during the same period. To repeat: 

 the experimental treatment apparently simply reduced the 

 number of generations during the 100 days. 



This same general result was obtained in Set C of Series I., 

 though of course here the lowering of the division rate was the 

 result of other causes. Figs. 3 and 4 show that endomixis 

 occurred in the fourth period of the four subcultures, A and At 

 and AE and AEt, although the rate of division and therefore the 

 number of generations was less in At than in A, and less in AEt 

 than in AE. 



This set of experiments, then, corroborates in a clear-cut 

 manner the general result derived from all the previous ones; 

 that is, general environmental changes, especially if they are 



