374 Problem of Rejuvenescence in Protosoa [June-September 



to conjugate, which he and Jennings had found to exist in different 

 races of this organism. Thus, Calkins emphasized the fact that 

 he could readily induce conjugation in his culture, whereas experi- 

 ments to secure conjugation in our cultures were without effect. 

 He, therefore, stated that "the two races cannot be compared in 

 regard to vitahty, since normal conjugation was prevented in the 

 conjugating race, whereas in the non-conjugating race there "has 

 been no artificial prevention of a normal process." 



With this issue raised, it was essential to determine whether our 

 race was actually non-conjugating. Accordingly, a more extensive 

 series of mass cultures were started from it, with the result that 

 conjugants were finally secured, thus demonstrating that this race 

 is a conjugating race when the proper conditions for conjugation are 

 realized. Therefore, there is no evidence extant that a non-conju- 

 gating race of Paramceciiim exists. 



In a recent paper, Calkins^ states that possibly his terms " con- 

 jugating " and " non-conjugating " were not happily chosen, and that 

 he merely meant to indicate that some races are more prone to con- 

 jugate than others. Admitting this Interpretation of his terms, they 

 express a fact. But this interpretation begs the question which his 

 Suggestion was advanced to explain. 



With this theory eliminated, the results derived from this cul- 

 ture demonstrate, we believe, that the very limited periods in which 

 Maupas, Calkins, and others observed degeneration, have no sig- 

 nificance for the question as to whether degeneration and death are 

 inevitable results of reproduction without conjugation. In other 

 words, this one positive result from this race outweighs all the 

 negative evidence derived from work on the infusoria, and justifies 

 the Statement that these organisms can live indefinitely, when sub- 

 jected to favorable environmental conditions, without conjugation 

 or artificial Stimulation. 



With conjugation eliminated as a necessary factor in the life 

 history, obviously the next point to be elucidated, if possible, was 

 the underlying factor inherent in the cell, the physiological expression 

 of which is the rhythm. Although morphological or physiological 

 variations that could be interpreted as the result of degeneration 



5 Calkins : Am. Naturalist, 1915. 



