340 H. S. JENNINGS 



Experiment 13 c. In order to test more fully the inheritance 

 of the differences in fission rate shown in table 33, certain lines 

 were next selected for propagation on a more extensive scale. 

 Beginning January 28, 1911, the attempt was made to propagate 

 16 parallel lines each of conjugant numbers 1, 2, 3, 11, 14 and 16 

 (of table 33), the purpose being (1) to determine whether the 

 results with 16 lines of a given number confirm those obtained 

 with but one line; (2) to discover whether there arise differentia- 

 tions within any of the series derived from a single individual. 

 This second point, as we have before seen, is fundamental for a 

 full understanding of the results thus far reached. 



These objects were not fully attained, owing to the cessation 

 of active propagation on slides in the race k, but certain results 

 of importance were reached. 



Conjugant lines. ' The sets derived from the different ex- 

 conjugants of table 33 showed great differences in vitality as 

 well as in rate of fission. Lines 1, 2, 3 and 11 began strongly, 

 16 parallel sets being derived from the original single set in one 

 to three days. With conjugant lines 14 and 16, on the other 

 hand, there was great difficulty in getting 16 sets established; 

 multiplication was extremely slow, and many of the sets died out 

 almost as soon as they were isolated. It was a week from the 

 beginning of the experiment before 16 sets were in operation in 

 conjugant lines 14 and 16. 



The relative rates of fission that had characterized the various 

 lines from the beginning continued to show themselves in the 

 sets of 16 from each line. The slower lines showed much greater 

 mortality than the faster ones. As fast as any set of a given line 

 died out it was replaced from another set of that line. The 

 number of deaths for each line was thus recorded. It will be 

 instructive to give for each of these lines of ex-conjugants the 

 number of fissions and the number of deaths, up to February 15. 

 This is done in table 22. 



The mortality in the slow lines increased from February 15 on, 

 so that on February 16 there were but three sets left (out of 16) 

 in line 14. By February 26 all the 16 sets of lines 14 and 16 were 

 dead, so that these two lines became extinct. In the meantime, 



