316 



H. S. JENNINGS 



We may divide this time into two periods of eight days each. 

 The results for the two sets are given in table 16, the four parallel 

 lines of each set being numbered (1) to (4). 



The table shows that for the total period, each of the four 

 lines of A multiplied more rapidly than any of the four lines of B. 

 For any of the eight-day periods, the lowest record for A is at 

 least equal to the highest for B, save in one single case. The 

 lines of A average for the entire period 20.5 per cent more 

 fissions than those of B. 



When we recall that B has conjugated recently, and three 

 times since A has conjugated at all, we see that the dropping 

 out of the conjugations has not unfavorably affected the rate of 

 reproduction in A. 



Dimensions. To the eye it appeared that B was a little larger, 

 under the same conditions, than A. As these belong to the same 

 pure strain, this is a matter of interest, as it would show that 

 hereditary differences in size may arise within the pure strain 

 possibly as a result of conjugation. A careful comparison of the 

 dimensions was therefore made. Keeping all under the same 

 cultural conditions, I first measured a number of individuals of 

 each set at the same age, choosing the age of thirty minutes after 

 fission. Three other measurements were taken; the results of 

 all are given in table 17. 



The fact that, as table 17 shows, B was larger at each of the 

 four measurements, seems to indicate that there has indeed 

 arisen a slight hereditary differentiation in size within the pure 



TABLE 16 



Experiment 9. Paramecium aurelia. Comparative number of fissions May 22 to 

 June 7, for two sets, one of which (B) has conjugated three times in series since 

 the other (A). 



