416 H. S. JENNINGS AND K. S. LASHLEY 



Experiment 1: Paramecium caudatum 

 This Journal, volume I4, 1913, page 286 



In Experiment 1 there were 31 pairs under propagation; one 

 member of one of the pairs was accidentally lost, so that for our 

 present purposes this pair must be excluded from consideration. 

 We have thus 30 pairs to deal with. None of them died during 

 the first week, showing that no deaths were due to handling or 

 the like while the pairs were united. The facts are given in table 

 29 of the paper just referred to (this Journal, page 379). 



It will be well to examine the condition of affairs at certain 

 intervals. 



At the end of the second week, five lines had died out, including 

 one pair. By formulae (1), (2) and (3), it is found that the most 

 probable number of pairs is 0, and that the chances are 5.06 to 1 

 against any pairs whatsoever being included. That is, the chance 

 for is 5.06 times as great as for all other possibilities together. 



At the end of the third week 15 lines out of the 60 were dead, 

 and among these fifteen were 4 pairs. Formula (1) shows that 

 the most probable number of pairs is 2; and formula (3) shows 

 that 2 pairs will occur in somewhat more than one third of all 

 cases, while 4 pairs would occur but once- in 25 cases, if the dis- 

 tribution of deaths had no relation to the pairing. The deviation 

 of the actual number from the most probable number is 2: by 

 our rule (5), we find that the chances are 5.96 to 1 against so 

 great a deviation as this, unless the distribution of deaths is actu- 

 ally connected with the pairing. 



At the end of the fourth week there are 18 lines dead, including 

 5 pairs. The most probable number is 3 pairs, which would occur 

 in 31 per cent of all cases, while 5 would occur in but 4 per cent, 

 if the distribution is random. The deviation from the expected 

 number has not increased during the fourth week. 



At the end of the experiment, five weeks from the beginning, 

 22 lines were dead, including 5 pairs, so that the number of pairs 

 has not increased. As set forth in the account of this experiment 

 in the paper referred to (page 287), the deaths during the fifth 

 week were due to mistaken cultural treatment; their distribution 



