REPRODUCTION OF THE HYPOTRICHOUS INFUSORIA 



215 



high as one division per day when averaged for five-day periods. 

 Although the division rate was low, the animals appeared to 

 be normal and healthy during the first three months of the cul- 

 ture, but about this time abnormal individuals began to appear 

 and subsequently the culture died. 



b. Culture Oh. This daily isolation culture, bred on the hay 

 infusion medium, was started October 27, 1911, by isolating an 

 individual from each of the four lines of the Ob culture, and was 

 carried until February 8, 1912, a period of 105 days, during which 

 time it passed through 159 generations. Diagram 2 shows graph- 

 ically the life history. A study of the graph and a comparison 



> 



Oct. -1911 



Nov 



Dec. 



150 



Jan -1912 



Feb 



Diagram 2 Graph giving the life history of Oxytricha fallax, Culture Oh, 

 showing the average daily rate of division of the four lines of the culture, again 

 averaged for five-day periods. Hay infusion culture medium. 



with diagram 1 shows that the life histories of these two cul- 

 tures were much the same. This culture maintained a slightly 

 higher division rate than did the Ob culture but died a few days 

 sooner. 



c. Culture Ove. This daily isolation culture, bred on the 

 'varied environment' medium, was started October 27, 1911, by 

 isolating an individual from each of the four lines of the Ob 



