PARAMOECIUM POSSESSING EXTRA VACUOLES 311 



The diameter of the vacuoles was obtained from a number of 

 fixed preparations some of which were sectioned. 



Multi-vacuoled race 



Average length 233 ii 



Average width 51 ^ 



.Volume 284, 493 cubic m 



Capacity of each vacuole 500 cubic m (diameter, 10 fi) 



To deliver themselves of a quantity of liquid equal to the volume of the 

 animal, at a temperature of 22°C., the 



2 vacuoled animals contract 284 times in 47 minutes at a 10 second rate 



3 vacuoled animals contract 190 times in 35 minutes at a 11 second rate 



4 vacuoled animals contract 142 times in 28 minutes at a 12 second rate 



5 vacuoled animals contract 114 times in 25 minutes at a 13 second rate 



6 vacuoled animals contract 95 times in 22 minutes at a 14 second rate 



The rate for the five and six vacuoled animals has been based on statistics 

 given above (page 309). 



Common race. Large individuals 



Average length 265 m 



Average width 53 m 



Volume 397, 690 cubic m 



Capacity of each vacuole 664 cubic n (diameter, 11 m) 



At the same temperature these animals require forty-nine minutes to pump 

 out a quantity of water equal to the volume of the animal. 



Small individuals 



Average length i 180 m 



Average width 53 /x 



Volume 194, 260 cubic m 



This lot would require twenty-three minutes for the same operation. 



It is evident from these figures that the new paramoecia are 

 superior to the larger forms in the quantity of liquid they can 

 excrete in a given time but in general are not quite equal to the 

 smaller races in this respect. I have been unable as yet to obtain 

 a wild race as large as these new animals to compare their re- 

 spective resistances and this will form an interesting part of 

 future work. I have, not attempted as yet to determine whether 

 there is any correlation between resistance to various substances 

 and the number of vacuoles but the addition of vacuoles in the 

 individuals as the culture ages and the conditions are presumably 

 becoming more unfavorable is a response that is very suggestive. 



