314 H. S. JENNINGS 



The experiment as a whole shows the fact that after conjuga- 

 tion the organisms are in a condition such that many may die, 

 while those that have not conjugated live; and the further fact 

 that the rate of reproduction is made slower by conjugation, 

 remaining in this condition for about two months. This is true 

 even when all the lines concerned belong to the same race (derived 

 originally from the same single individual). 



Experiment 7: March 29 to April 10, 1910: Paramecium aurelia 



On March 29 there was a conjugation in the progeny of a 

 single ex-conjugant of January 29; the relation of these to the 

 remainder of the experiments will be seen from the diagram, 

 figure 1. These animals belong to the branch B of the diagram. 

 They have conjugated once, and probably twice, since those of 

 the branch A, which are known not to have conjugated since 

 some period before March 4, and to have been ready for conju- 

 gation March 4, A comparison as to rate of fission was made 

 between these non-conjugants of branch A and the conjugants 

 of March 29, branch B, lasting for nine days (April 1 to April 10). 



Of the conjugants of branch B, \9 lines were in progress; their 

 average rate of fission per line for the nine days was 1.409 per 

 day. Of the non-conjugants (branch ^), 21 lines were in progress; 

 their mean rate for the nine days was 1.455 per day. 



Thus the non-conjugants of branch A give no indication as 

 yet of injury through having omitted conjugation. The differ- 

 ence in rate between conjugants and non-conjugants was slight, 

 but in favor of the non-conjugants. 



Experiment 8: April 9 to April 30, 1910: Paramecium aurelia 



On April 9 there was conjugation among the progeny of one 

 of the ex-conjugants of Experiment 7 (conjugation March 31) 

 shown in branch B of figure 1. There have now been seven 

 generations of inbreeding in this branch; and it has conjugated 

 twice (probably three times) since those of branch A have con- 

 jugated at all. What difference will this make between the rate 

 of fission in the members of the two branches? 



