FISSION RATE OP STYLONYCHIA PUSTULATA 



469 



lines had been subjected to opposite selection. During this 

 whole experiment the animals were transferred to fresh slides 

 daily as described at the beginning of this paper. 



The results of Experiment 1-B, are so important that they 

 are set forth in some detail in table 6. This table gives the 

 actual number of generations produced by each fast and each 



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_/ 



I i I I I I I I I I I I 



Fig. 6 Curves of variation in actual number of fissions of the two sets of 

 lines of Experiment 1, Part 3. The ordinates give the number of lines, the 

 abscissae the number of generations produced during the thirty days. The con- 

 tinuous line is the curve of the fast-selected set, the broken one is that of the 

 slow-selected set. 



slow line during each ten-day period of the experiment, and the 

 difference between them. This difference is given as a positive 

 quantity when the fast line has produced more generations than 

 the corresponding slow one and negative when the reverse is 

 the case. The latter occurred only thirty-one times among the 

 whole two hundred and seventy differences. In twelve of the 

 lines it did not occur at all; in nine lines, once; in six lines, twice; 



