SCIENTIFIC PROCEEDINGS. 



Abstracts of the Communications. 

 Forty -ninth meeting. 



University and Bellevue Hospital Medical College. May i$, IQI2. 

 President Ewing in the chair. 



70 (679) 



The effect of chemicals on the division rate of protozoa. 

 By GARY N. CALKINS. 



[From the Department of Zoology, Columbia University.] 



These experiments have been carried out during the past year 

 for the purpose of finding out whether the products of nucleo- 

 proteid breakdown have any effect upon the division rate of free- 

 living cells, the ultimate aim being to get some light on the con- 

 trolling factors of cell division. 



Two ciliated protozoa were used. One, Actinobolus radians 

 Stein, lives exclusively on a diet of Halteria grandinella, another 

 ciliate. The other, Blepharisma undulans Stein, lives on bacteria. 

 Four control lines of each have been watched, fed, and the number 

 of divisions recorded daily, and curves based upon the averaged 

 division rates for five day periods, give the fluctuations in vitality 

 of the organisms as measured by the division rates. Periods of 

 depression, and of decreasing and increasing vitality have been 

 clearly marked. Individuals for experimentation were in all 

 cases sister cells of the control lines of the same dates. 



The chemicals used included various amino acids, nucleins, 

 and their derivatives, for many of which I am indebted to Dr. 

 Levene and Dr. Walter Jones. In each experiment four strengths 

 of chemical were used after empirical determination of the lethal 

 dose. The number of divisions of all four lines were averaged 



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