I9I2] Lorande Loss Woodruff 403 



It has just been shown that there are normal rhythmic fluctua- 

 tions in the rate of reproduction of Paramceciiim, even when sub- 

 jected to the most constant environmental conditions, and that the 

 rhythms are due to some unknown inherent factor in cell phe- 

 nomena. The rhythms, then, are independent of temperature. 

 Records of a line of cells with the descending phase of a rhythm 

 predominant, subjected to 28°, and a line of cells with the ascend- 

 ing phase of a rhythm predominant, subjected to 24.5°, may actually 

 show (during the persistence of the rhythm) a more rapid rate of 

 division at the lovver than at the higher temperature. Accordingly, 

 in this study it has been necessary to be sure that the animals sub- 

 jected to the different temperatures were in comparable phases of 

 the rhythm, or that the experiments were sufficiently prolonged to 

 include one or more complete rhythms. It is clear that the rhythms 

 are a factor which must be taken into account in any study of the 

 physiology of this animal. 



The first point to determine was the general effect of various 

 temperatures on the protoplasm of this culture, and accordingly 

 subcultures, comprising eight lines of " sister " cells, were subjected 

 to the following temperatures for forty days or until the tempera- 

 ture proved fatal : 8°, 16°, 21°, 24.5°, 28°, and 32° C. The results 

 were clean cut and showed that the organisms are adapted to a con- 

 stant temperature below 32° and above 21° C. A careful study of 

 the daily records indicates that the Optimum temperature zone is 

 between 24° and 28.5°. 



Having determined the optimum temperature zone, the tem- 

 perature coefficients for extreme points within this zone were 

 studied. Eight lines of cells at 28° for 40 days gave a total of 527 

 divisions, and eight lines of cells at 24.5° for 40 days gave a total of 

 370 divisions. Employing the extra- and interpolation logarithmic 

 formula frequently used for such computations, which takes the 

 form 



a 



10 



-(f:)"^ 



in which Q^q is the coefficient of the increase in reaction velocity 

 for a rise of 10° C, and the Symbols K^ and Kq represent constants 



