420 H. S. JENNINGS AND K. S. LASHLEY 



Thus the results in this experiment are, so far as they go, 

 against the hypothesis of sexual differentiation, but do not give 

 definite positive evidence of any other relation between the 

 members of pairs. 



Experiment 13: Paramecium aurelia 

 This Journal, volume 14, 1913, page 829 



In this experiment, carried on with the pure strain k, there were 

 78 lines derived from 39 pairs of ex-conjugants; these were culti- 

 vated for only a week. During this time there died out 20 lines, 

 including 4 pairs. The most probable number of pairs, with a 

 distribution of deaths having no relation to the pairing, is 2. The 

 probability of 4 pairs is 0.142, so that they would occur, as a 

 result of chance, once in seven cases. 



Thus the number of pairs that died is here, as usual, greater 

 than would be expected if the distribution of deaths had no rela- 

 tion to the pairing. 



Summary: on the relation of the survivals and deaths to pairing 



In order to give evidence of sexual differentiation between 

 the members of pairs, it is necessary that the number of cases 

 in which both members of pairs die or survive should be less than 

 would be expected if the distribution of deaths had no relation to 

 the pairing. In no case, among those of which statistics are 

 available, as set forth in the preceding, is this the state of affairs. 

 The nearest approach to it is in my experiment 2 (page 417), where 

 after two weeks the number of pairs dead was one more than the 

 most probable number, though at the end of the experiment the 

 number dead was one less than the most probable number. In 

 all other cases the number of pairs that died and the number that 

 survived, was equal to, or greater than, the number that would be 

 expected if the distribution of deaths had no relation to the pair- 

 ing. In most cases it is greater than would be expected. 



Thus the distribution of survivals and deaths gives no evidence 

 of sexual differentiation between the members of pairs. 



