70 RHODA ERDMANN AND LORANDE L. WOODRUFF 



TABLE 2 

 Culture Y 



III fa and IV ac, were killed in the descending ph^se of the 

 process. Sub-hne IV aa was killed after the cHmax. 



Thus although cytological indications of the reorganization 

 process were not observed in certain of the lines and sublines of 

 Culture Y at the time of extinction, nevertheless this extinction 

 was synchronous with the process as actually observed in other 

 lines and sublines from the 136th to 143d generations, 184th to 

 191st and 202d to 209th generations. These periods clearly are 

 critical ones in the life of this culture (table 2) . 



However our culture of Paramaecium aurelia was able to 

 undergo the reorganization process frequently and with apparent 

 facility under daily isolation methods, and therefore the number 

 of lines which were eliminated by death during the phenomenon 

 was relatively small (cf. '14, III, table 1, p. 462). 



From all our work the conclusion evidently follows that before 

 cytological signs of reorganization are discernible in the cell the 

 physiological conditions for its onset are in evidence. 



Culture Z was bred from September 20, 1914, and Culture M 

 from .January 7, 1915, to the end of our study. Culture Z under- 



