Races of Paramecium. 



539 



were not adapted to the requirements of this rarce, though for A.- 

 they were quite suitable. 



A still more marked case of the same sort is given by the race 43- 

 This consisted of large animals of the caudatum group, all derived 

 from a single wild specimen. At the time of the experiment it 

 was flourishing in a culture consisting of timothy hay in water. 

 When transferred to the slide cultures, in which the hay infusion 

 was changed every day, the animals divided a few times, then died. 

 It was thus impossible to carry these through the fission experi- 

 ment parallel with the others, in order to determine their relative 

 rate of fission. In the case of the first two individuals tested, four 

 series from each were carried, making eight lines in all. At first 

 all multiplied rapidly; then at about the fifth day the rate of fission 

 decreased; the animals showed abnormal conditions, and all of 

 the eight lines died after seven to thirteen generations. The 

 following table 6 shows the history of the eight lines of this race 



TABLE 6 



History of the eight lines of the race 4^, from the beginning of the experiment 

 till death, showing the number of fissions per day, compared with four lines of the 

 race L2 at the same time and under the same conditions. 



(The dashes indicate death of the line. The numbers and dashes in parentheses 

 show that the series was supplied by taking an individual from one of the surviving 

 lines of the same race, till this also died. The lines of Li flourished long after the 

 period shown, till the experiment was discontinued.) 



