PERIODIC REORGANIZATION IN PARAMAECIUM 429 



('11 c) from a study of the temperature coefficient of the rate 

 of reproduction of this culture which showed th'at the rate of 

 cell division of Paramaecium is influenced by the temperature 

 at a velocity similar to that for a chemical reaction — except 

 when the rhythms interfere. 



The results from the study of this pedigreed race of Para- 

 maecium aurelia have led Woodruff to conclude that this organ- 

 ism, when subjected to suitable culture conditions, has the power 

 of unlimited reproduction by division without conjugation or 

 artificial stimulation — ^the only necessary variations in the rate 

 of reproduction being the normal minor periodic rise and fall 

 of the division rate (rhythm), due to some unknown factor in 

 cell phenomena, from which recovery is autonomous. 



Calkins and Gregory ('13, p. 507) ''.... do not 

 share his optimism, however, and can only say that while his 

 results are remarkable, his race is not yet dead. Is there any 

 clue to the particular make up of this race of Paramaecium 

 aurelia?" Accordingly Calkins sought the explanation of the 

 diametrically opposite results derived from his and from Wood- 

 ruff's cultures of Paramaecium in variations in the tendency to 

 conjugate which have been observed by Jennings ('10) and him- 

 self to exist in different races of this organism. Thus he empha- 

 sized the fact that he could readily induce conjugation in his 

 culture whereas experiments to secure conjugation in Woodruff's 

 culture were without effect. Calkins, therefore, stated that ''the 

 two races cannot be compared in regard to vitality, 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." ''Woodruff's Paramaecium aurelia is evi- 

 dently a Paramaecium Methuselah belonging to a non-conju- 

 gating line the life history of which is not known in any case." 



However, conjugation was finally secured in a mass culture 

 seeded from Woodruff's race ('14) thus demonstrating that this 

 race is a conjugating race when the proper conditions for its 

 consummation are realized. Therefore, there is no evidence 

 extant that a non-conjugating race of Paramaecium exists. 



