ENDOMIXIS IN PARAMAECIUM ATJRELIA 51 



and on the other increased the rate of their own metabolism; 

 supports the view of Woodruff and Erdmann as to its rejuvenat- 

 ing function, and suggests that the macronucleus may serve in 

 part as a reservoir of waste products which are distributed 

 through the cells in endomixis and can then be excreted through 

 the contractile vacuoles. The action of distilled water is not 

 clear. It may possibly be a starvation effect, as the number of 

 bacteria are materially reduced in these cultures. It may on the 

 other hand be a toxic effect due directly to the action of the dis- 

 tilled water. The latter hypothesis is supported by the result 

 in experiment 10, where the animals were not killed so long as 

 there was a trace of the old culture on the slide, but died almost 

 immediately after washing in, followed by transfer to pure dis- 

 tilled water. 



This interpretation is supported by the fact that Paramaecium 

 will not withstand direct transfer to distilled water, but may be 

 adapted to it to a certain extent by increasing the dilution of the 

 culture gradually, and by the fact that in one instance (Xb-4/11) 

 the race died out while numerous food vacuoles were present. 

 It also agrees with the work of previous investigators. 



That a temporary reduction of growth should be associated 

 with endomixis is only to be expected in view of the great 

 changes taking place at this time within the cell. Paramaecium 

 can however undergo brief depression periods without the in- 

 tervention of endomixis, as proven by the graphs of Woodruff 

 and Erdmann and by my own results in this investigation; 

 while endomixis does not necessarily rejuvenate as shown by 

 my results in experiments 2, 7 and 8. These facts show that 

 other factors than endomixis are involved in determining the 

 division rate of Paramaecium. In the case of some of the ex- 

 periments, notably 7 and 8, where occasionally several days 

 ensued without any division, it is possible, though not probable 

 that endomixis occurred more frequently than I have recorded 

 it. Even so, however, my conclusions would be emphasized 

 rather than negatived thereby. Whether we may consider en- 

 domixis as a reproductive, as well as a rejuvenating process, 

 or consider it the equivalent of parthenogenesis in the Metozoa, 



