180 RUTH L. PHILLIPS 



Woodruff and Erdmann ('14) showed that what they describe 

 as rhythms in Paramecium are due to the internal reorganization 

 of endomixis. The study of Paramecium with reference to food 

 seems to show that minor fluctuations occur in the course of 

 rhythms which, hke these latter, are largely independent of en- 

 vironmental conditions. Such fluctuations have been noted by 

 others, but have been attributed to such unknown factors as 

 variation in food or medium. In my experiments food and 

 medium were as exactly controlled as possible. All the organisms 

 were subjected to the laboratory temperature, but, as has been 

 pointed out, since these fluctuations took place when there was 

 little change in the temperature, it would appear that this factor 

 had little to do with their occurrence. More carefully controlled 

 experiments are necessary to determine this. There appear, how- 

 ever, to be fluctuations in the metabolism not directly connected 

 with the rhythms of endomixis, but, like them, due to some in- 

 trinsic characteristic of the protoplasm. These fluctuations 

 occur in all cultures irrespective of changes in food or medium 

 and do not appear to be directly due to environmental factors, but 

 rather to be manifestations of protoplasmic changes. This 

 subject needs careful investigation before definite conclusions 

 can be drawn. 



Having determined that mixtures of bacteria are more satis- 

 factory than pure cultures, one is led to inquire if such a mixture 

 should be kept constant. Such experiments as were performed 

 in testing the effect of change of food showed that under the 

 conditions obtaining, change of food was usually accompanied 

 by so much disturbance in the metabolism that no marked in- 

 crease in division rate resulted, and that with these mixtures at 

 least constancy of diet was preferable to change. This result 

 with a known food supports the contention of workers with 

 chance mixtures, namely, that every effort should be made to- 

 ward maintaining a uniform bacterial content in media used for 

 growing Paramecium. 



The behavior of Paramecium in sterile media is of interest for 

 two reasons. It demonstrates that these animals are incapable 

 of utilizing for food any substances which may be dissolved in 



