RHYTHMS AND ENDOMIXIS IN VARIOUS RACES OF 

 PARAM^CIUM AURELIA. 



LORANDE LOSS WOODRUFF, 

 OSBORN ZOOLOGICAL LABORATORY, YALE UNIVERSITY. 



In view of the fact that the study of rhythms and endomixis 

 in Paramceciuin was made chiefly on my long pedigreed race of 

 Paramcecium aurelia, it has been suggested by a couple of 

 authors that the reorganization process may be something 

 peculiar to this race, perhaps resulting from long subjection to 

 conditions which preclude the possibility of conjugation. This 

 assumption, however, was rendered exceedingly improbable from 

 the data presented by Woodruff and Erdmann 1 in their original 

 complete paper which showed that ''the same reorganization 

 process was resumed in all the lines within a relatively short 

 time after conjugation" was allowed to occur in a subculture of 

 the main race, and also that the phenomenon was observed 

 early in the culture of a race which was secured by Erdmann 

 from Berlin, Germany. Further, Erdmann and Woodruff 2 in a 

 paper on endomixis in Par am cerium caudatum stated incidentally 

 that endomixis had been found in two new races of Paramcecium 

 aurelia immediately upon their isolation. 



The above data more than justify the early conclusion of 

 Woodruff and Erdmann that "this reorganization process is a 

 normal phenomenon and probably occurs in all races of the species 

 Paramcecium aurelia," 3 but in connection with other work on 

 Paramcecium it has been necessary to employ various races for 

 study and the purpose of the present paper is to record briefly 

 the additional data bearing on the points under discussion. 

 This may be most readily accomplished by considering seratim 

 the graphs of the life histories which- show the rhythms and 

 the occurrence of endomixis in the respective cultures. Since 



1 Journal of Experimental Zoology, Vol. 17, No. 4, 1914. 

 -Journal of Experimental Zoology, Vol. 20, No. 2, 1916. 

 3 Ibid., 1914, p. 474. 



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