418 



H. S. JENNINGS AND K. S. LASHLEY 



TABLE 37 



Death rate in relation to pairing, in experiment 2. 



probability for the occurrence of the most probable number, as 

 well as of the actual number, in order that these may be compared. 

 Thus the data of this experiment give no evidence for sexual 

 differentiation, nor for any other special relation of the two 

 members of pairs; they are what might be expected if the distri- 

 bution of deaths were purely random. This is not surprising, in 

 view of the high mortality; the deaths were evidently due mainly 

 to extrinsic causes. 



Experiment 3: Paramecium caudatum 

 This Journal, volume 14, 1913, page 300 



In this experiment there were 46 lines, derived from 23 pairs. 

 Out of these, 11 lines died out during the four days of the experi- 

 ment. The number of pairs among these was 1, and this is the 

 most probable number that would be found, if the incidence of 

 death had no relation to the pairing. 



There were also in this experiment 50 lines derived from 25 

 spHt pairs; of these 35 lines died out in the four days. .Among 

 these were 13 split pairs. Applying our formulae, we find that 

 the most probable number of pairs is 12, although 13 is nearly as 

 probable. The probabihty for 12 is 0.369; for 13 it is 0.260, so 

 that 13 would occur little less often than 12. 



