ENDOMIXIS IN PARAMAECIUM AURELIA 41 



Experiment 4 (fig. IV) 



In this experiment line IV was branched off from II on 4/13 and 

 carried for twenty-six generations with infrequent changes to fresh 

 slides. After 5/9 slide changes were made daily until the termination 

 of the experiment on 6/11. Between 3/5, the date of appearance of the 

 last endomixis in II, the parent line, and 5/1 when the first endomixis 

 occurred in line IV, there was a period of forty-five generations; while 

 from 5/1 until 6/9 when the next endomixis ensued in line IV, there 

 was a period of seventy-six generations, an increase of thirty-one. 



Experiment 5 (fig. V) 



On 5/13 line V was branched off from IV and carried without 

 change of slide until 5/23, an endomixis ensuing on 5/17, twenty-four 

 generations after the last endomixis in line IV from which this line 

 was branched. Here we see that instead of a period of seventy-six 

 generations between endomixis, as occurred between 5/1 and 6/9 in 

 line IV, the sister line of V, a period of but twenty-four generations 

 occurred. 



Experiment 6 (figs. VI and Via) 



On 4/15 line VI was branched off from line II and carried with occa- 

 sional slide changes in a weak solution of NH 3 in beef extract 7 until 

 4/29 in an effort to induce endomixis, when it was transferred to beef 

 extract on a fresh slide, and carried to 5/6 with one change of slide, 

 after which it was changed daily until 6/16. Endomixis occurred 

 on 4/23, forty-eight generations after its last occurrence in line II, 

 and one on 6/14, 102 generations later. On 5/9 line Via was branched 

 off from line VI and carried with infrequent slide changes until 6/17. 

 An endomixis ensued on 5/15, 19 generations after the last in line VI. 

 Here we find a period of but 19 generations between endomixis in a 

 line carried with but few slide changes, while in one with daily changes 8 

 one hundred and two generations intervened. 



Experiment 7 (figs. Vila and b) 



In this experiment two lines Vila and b were carried with infre- 

 quent slide changes for thirty and twenty-six generations respectively 

 in an old culture in which Paramaecia and other Infusoria had been 

 living for several months, the average interval between endomixis for 



7 Exact strength not recorded. 



• Except the first eleven generations 4/23 to 5/6. 



DESCRIPTION OF FIGURES 



The graphs show the daily division rate, vertical divisions representing one 

 division and horizontal divisions one day. 'x' signifies the occurrence of endo- 

 mixis. 'x?' indicates uncertainty regarding its occurrence and '?' uncertainty 

 regarding the number of divisions. 



