36 R. T. YOUNG 



16 and 17, pp. 479 and 480) show moreover that periods of low 

 division rate may ensue without the occurrence of the rejuve- 

 nating process. I do not here refer of course to the low division 

 rate period in line VI which was induced by bacteria, but rather 

 to that just preceding the first occurrence of the process in line VI 

 (text fig. 16) and to the two low periods in line III (text fig. 17) 

 between the first and second occurrence of the process, and that 

 just preceding its last occurrence in this line. They also show 

 that the process may commence, but not continue to its comple- 

 tion (p. 458). The culture method employed by these authors 

 renders their conclusions uncertain. The frequent changes of 

 culture fluid (i.e., after every two divisions) to which they sub- 

 jected their Paramaecia might have enabled these to survive the 

 depression periods through which they passed, and enter upon 

 new periods of activity, and at the same time to recover from the 

 nuclear disturbance which they simultaneously experienced. 

 Calkins ('02 et seq.) was able several times to rehabilitate his 

 Paramaecia by subjecting them to changes of culture media, and 

 it is a well known experience that Paramaecia will develop rap- 

 idly when transferred from an old to a fresh culture. Thus it is 

 not unreasonable to ask whether the transfer to a fresh culture 

 was not what enabled specimens to survive their periods of de- 

 pression and enter upon subsequent ones of active reproduction. 

 In order to prove their point it would be necessary to carry the 

 Paramaecia through the reorganization process in the same 

 culture without the frequent culture changes made by them. 



While examining a culture of Paramaecium aurelia for class 

 work I found the multinucleate condition occurring commonly, 

 and since then have found it frequently in cultures derived from 

 the original material as well as from other sources, and in P. 

 cauda turn as well as aurelia. 



In order to examine further the significance of multinuclearity, 

 and to test the possibility of its experimental induction, I have 

 performed a series of experiments which I shall here describe, 

 and which I have designed to answer the following questions: 



1) Can endomixis be experimentally induced? 



