SCIENTIFIC PROCEEDINGS. 



Abstracts of Communications. 



Fifty-seventh meeting. 



Rockefeller Institute for Medical Research, February 18, 1914. 

 President Ewing in the chair. 



43 (860) 



Complete periodic nuclear reorganization without cell fusion in a 

 pedigreed race of Paramaecium. 



By Lorande Loss Woodruff and Rh. Erdmann. 



[From the Osborn Zoological Laboratory, Yale University.] 



This preliminary communication presents the main results 

 derived from the cytological study of specimens preserved through- 

 out the life of a pedigreed race of Paramaecium aurelia, as well as 

 of a series of specimens preserved daily, during the past four 

 months, from subcultures of this race carried under constant 

 environmental conditions. 



During the past six and three quarter years this pedigreed race 

 has been carried with the following chief results: 



1. More than 4,250 generations have been attained to date 

 (February 18, 1914) without the fusion of individuals or the advent 

 of periods of marked physiological depression, though periodically 

 well-defined normal morphological changes have occurred. 1 This 

 demonstrates that the so-called "life cycle" of Paramaecium is non- 

 existent when proper environmental conditions are supplied. 2 



2. Minor periodic fluctuations in the division rate, termed 

 rhythms, have been demonstrated, recovery from which is auto- 

 nomous. 3 



1 Woodruff, Amer. Naturalist, XLII, 1908, p. 526. 



2 Woodruff, Biol. Bull., XVII, 1909, p. 287; Proc. Soc. Exp. Biol, and Med. 



IX, 1912, p. 121. 



3 Woodruff, Archiv fur Protistenkunde, XXI, 191 1, p. 263. 



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