50 



R. T. YOUNG 



rate and percentage of multinuclearity regardless of the kind of 

 culture used in the isolation experiments. This objection more- 

 over will not hold in regard to comparisons between those ex- 

 periments in which the same culture media were employed 

 (compare experiment 20 with 21 and 22 with 23 and 24). 



These experiments further demonstrate the interesting fact 

 that there is no correspondence between death rate and multi- 

 nuclearity even when the specimens are isolated in the parent 

 culture (compare experiments 22 and 24). 



In most cases of the death of Paramaecium in isolation cul- 

 tures in which I have examined the nuclear condition of the 

 dead animals I have found it mononucleate, further proving 

 the absence of a positive correlation between multinuclearity 

 and death. 



What function then may be ascribed to endomixis? It is 

 evidently a necessary process in the life of the race, occurring at 

 more or less regular intervals. The fact that in the experi- 

 ments above described the frequency of multinuclearity was 

 markedly increased by impurity in the culture medium and by 

 increase of temperature; conditions which, on the one hand sub- 

 jected the animals to the influence of metabolic end products, 



16 These percentage counts were made from the same culture — in experiment 

 20, five days before and in experiment 21 two days after the isolations. 



17 In parent culture. 



18 In beef extract. 



19 Percentage count made from slides prepared one and two days preceding the 

 isolations. 



20 Percentage count made from slides prepared one and two days after the 

 isolations. 



