448 



GEO. T. HARGTTT AND WALTER W. FRAY 



TABLE S 



Growth of Paramecium aurelia in pure cultures of bacteria, in 0.1 per cent hay 

 infusion. Figures represent the number of divisions; ^ animals abnormal in appear- 

 ance; all alive at the end of the period recorded 



division being only 0.454 per day; this was only about one half 

 the rate of a similar line in a previous experiment (0.909 per 

 day). 



Since the paramecia fed on B. subtilis and on B. fluorescens 

 began to appear dark in color as though filled with undigested 

 food (these are marked as abnormal in the table) they were 

 sterilized by washing and both lines placed on a diet of Bacillus 

 flavescens (Bact. V). In the case of the line transferred from 

 B. subtihs to B. flavescens the rate remained the same and the 

 abnormal appearance changed to normal. The B. fluorescens 

 transferred to B. flavescens dropped in rate of division slightly 

 (0.454 to 0.333 per day). The rate of division of the same line 

 of paramecia fed on this same B. flavescens in a previous experi- 

 ment had been 0.857 per day, though death occurred within a 

 week in that case. In the series recorded in table 8 all of the 

 protozoa were alive at the end of the experiment. 



