158 Life and Death, Heredity and Evolution 



lines of descent, we find it to be extremely uniform. For 

 periods of 21 days we find the number of fissions of the 

 first 24 lines to be those given under "Non-con jugants," 

 a and b, in the following table. (The two individuals, a 

 and b, of the non-con jugants, had begun to mate, but were 

 separated before the mating process occurred.) In these 24 

 lines the number of fissions in 21 days varied only from 21 

 to 26 ; it is on the whole very uniform. One finds little or 

 no indication of inherited differences between the families; 

 they run very evenly. 



Now we allow a large number of the individuals to con- 

 jugate, then follow the rate of fission for 88 lines derived 

 from these mates. We find that there are now great dif- 

 ferences between the separate families with respect to fission 

 rate. In the table the two last columns, headed "Con- 

 jugants," give the number of fissions for 24 lines descended 

 from pairs of conjugants, for the same 21 days as for 

 those that have not conjugated. The two sets (Non- 

 con jugants and Conjugants) were kept throughout under 

 the same conditions. 



Table 



Comparative fission numbers in 21 days of Conjugants and Non- 

 con jugants derived from a single race E (from Tables 34 and 35; 

 Jennings, 1913). In the non-con jugants, a and b represent two indi- 

 viduals that had begun to mate, but were separated before mating was 

 accomplished. In the conjugants, a and b are the two mates from one 

 pair. 



Non-con jugants Conjugants 



Pair a b a b 



1 25 23 30 29 



2 24 23 25 24 



3 24 24. 29 28 



4 24 25 10 9 



5 23 24 8 10 



6 22 25 24 24 



7 22 26 29 28 



8 31 25 25 24 



9 24 25 30 27 



10 22 26 26 26 



11 23 24 28 27 



12 25 24, 11 9 



