402 Pedigreed Race of Paramcccimn [Mar. 



expect to find them more clearly brought out vvhen the cell is free 

 from extraneous influences. 



The division rate at the different temperatures shows that tem- 

 perature, as is well known, markedly influences the rate, but it also 

 shows that the rhythms persist — the reproductive activity being, as 

 if were, pitched at a higher or lower scale, but its character in no 

 wise altered. 



The data just presented prove that it is not possible by constant 

 environmental conditions to eliminate the rhythms and to resolve 

 the graph of the multiplication rate into an approximately straight 

 line. It therefore seems justifiable to conclude that there are 

 inherent rh}1;hmical changes in the phenomena of the cell which are 

 brought to view still more clearly when not influenced by external 

 factors. 



Finally, the data justify the conclusion that the cells of this 

 pedigreed race of Paramcucium aiirelia have the potentiality to 

 perpetuate themselves indefinitely by division (under proper envi- 

 ronmental conditions) — the only necessary variations in the rate 

 of reproduction being normal minor periodic rises and falls of the 

 fission rate, due to some unknown factor in cell phenomena. 



IV 



Considerable data have been accumulated In regard to the effect 

 of different temperatures on living processes in general, and on the 

 rate of reproduction of Infusoria, but comparatively little work 

 has been undertaken with special reference to the temperature 

 coefficient. Vital phenomena are undoubtedly largely the result of 

 chemical reactions taking place in the living substance, and conse- 

 quently one would expect that the well-known law of van't Hoff 

 and Arrhenius should apply, i. e., for each increase of io° C. the 

 rapidity of a reaction is increased from two to three times. It was 

 therefore decided to make a detailed study of the effect of several 

 constant temperatures on the rapidity of cell division of this culture 

 of ParamcEcium when subjected to a 'constant environment' of 

 beef extract.^^ 



" Woodruff and Baitsell : The temperature coefficient of the rate of repro- 

 duction of ParamcBcium aurelia. Amer. Joum. Physiology, vol. 29, no. 2, 191 1. 



