FISSION RATE OF STYLONYCHIA PUSTULATA 



479 



Horlick's malted milk; and all those remaining in the 'slow' 

 concavities were similarly treated. These two mass cultures 

 were placed side by side on the laboratory table and allowed to 

 propagate for twelve days. Every three days 25 cc. of boiled 

 and cooled spring water was added to each to compensate for 

 evaporation. The animals placed in these mass cultures were 

 taken from Experiment 1-B, and hence had been subjected to 

 opposite selection for eighty days and balanced selection for 



Fig. 10 Curves of variation of the lines of Experiment 1, Part 4 (continuous 

 selection). The ordinates give numbers of lines, the abscissae the generations 

 produced during the fifty days of the experiment. The continuous line is the 

 curve of variation of the fast set, the broken one the curve of the slow set. 



forty days; they were now allowed to remain in mass cultures 

 for twelve days. 



On March 17, 1914, thirty individuals were taken from the 

 mass culture of fast lines and isolated on slides and thirty indi- 

 viduals were also isolated from the mass culture of slow lines. 

 These sixty lines were then subjected to balanced selection for 

 a period of fifty days, the transfer to fresh slides being made 

 daily. 



