6 4 



Scientific Proceedings (56). 



38 (855) 



Further light on the conjugation of Paramecium. 

 By Lorande Loss Woodruff. 



[From the Osborn Zoological Laboratory, Yale University.] 



On December 7, 1913, conjugation occurred in a mass culture 

 started from my pedigreed race of Parametrium aurelia 1 at the 

 4,i02d generation, showing that this race is a conjugating race 

 when the proper conditions for its consummation are realized. 2 



Variations in the tendency to conjugate which are exhibited 

 by pure races and lines of Paramecium have led Calkins to the 

 view that herein lies the clue to the directly opposite results 

 derived from his races and from mine. 3 "The race that I worked 

 with in 1 90 1 was a conjugating race which died out in the 742d 

 generation. Woodruff's long line of over 3,500 generations is 

 a non-conjugating race and 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 

 was no artificial prevention of a normal process." 4 



Since conjugation has now occurred in animals from my race 

 there is no evidence extant that a "non-conjugating" race of 

 Paramecium exists. 



1 The possibility of conjugation occurring in the main lines of the pedigreed 

 race is prevented by daily isolation of the individuals. For details of this race cf. 

 Woodruff: Proc. Soc. Exp. Biol, and Med., 1912, Vol. ix, p. 121. 



2 Details of this experiment will appear in the Journ. Exp. Zoology, Feb., 1914. 



8 G. N. Calkins (J. Exper. Zobl., Nov., 1913, p. 509): "The life history of con- 

 jugating lines has shown that if conjugation is prevented, the race dies out." L. L. 

 Woodruff (Archiv f. Protistenk., Jan., 1911, p. 266): "I believe this culture shows 

 clearly that Paramecium aurelia, when subjected to suitable culture conditions, has 

 the power of unlimited reproduction by division without conjugation or artificial 

 stimulation." 



4 Calkins, Proc. Soc. Exper. Biol, and Med., Vol. 10, 1913, p. 67. 



