EFFECT OF CONJUGATION 343 



Experiment 14: Paramecium aurelia 



This was a direct continuation of the foregoing, dealing with 

 the rapidly multiplying line 1 of the non-conjugants. On March 

 20, 1911, a considerable number of these were placed in a watch 

 glass; on March 22, conjugating pairs were found among these. 

 Of these 48 pairs were isolated, making after separation 96 lines, 

 which were cultivated on slides as usual. At the same time there 

 were in progress 64 lines of those that had not conjugated, and 

 to these were now added 48 more. Thus we have now propagat- 

 ing, under identical conditions, 96 lines of ex-conjugants and 144 

 lines of non-conjugants, all derived from individual No. 1 of the 

 non-conjugants of the previous experiment. 



Conditions were unfavorable for multiplication, the tempera- 

 ture being low and the university buildings not heated. Of the 

 96 lines of conjugants, all but four died without dividing; that 

 is, 95.8 per cent. Of the 48 non-conjugants set at the same time, 

 27, or 56.25 per cent died without dividing. 



By March 31, nine days after conjugation, all but 4 of the 96 

 conjugant lines were dead, while 27 of the 48 non-conjugant lines 

 were dead. Of the entire 144 non-conjugant lines, kept under the 

 same conditions as the conjugant ones, 37 had died during the 

 same period. Thus the proportion of deaths was, for the con- 

 jugants, 95.83 per cent; for the non-conjugants 25.69 per cent. 



This experiment shows that under such unfavorable conditions 

 the animals that have recently conjugated are much less resistant 

 than those of the same descent that have not recently conjugated. 



Experiment 15: inherited differentiation produced by conjugation: 

 Paramecium caudatum 



In the summer of 1912, after several months spent in vain 

 attempts to repeat with the race k the essential features of 

 Experiment 13, under such conditions as would show beyond 

 question whether all the inherited differentiations were due to 

 conjugation or not, a successful experiment for this purpose was 

 carried through with a race of Paramecium caudatum which I 

 called E. 



THE JOURNAL OP EXPERIMENTAL ZOOLOGY, VOL. 14, NO. 3 



