TOXIC ACTION OF KCN ON PARAMECIUM AND DIDINIUM. 223 



TABLE VI. 



Paramecia, YEAST-FED AND STARVED. 



A. Time between division and killing the two sisters, one of which had lived in 

 tap water, the other in tap water and fresh yeast suspension. 



B. The averages of the survival times of 30 fed Paramecia. 



C. Since all those left with food for 12 hours divided, the experiment was con- 

 tinued without food for 15-, 19- and 25-hour intervals. So that the numbers for 

 15, 19 and 25 hours, rows C and D represent average survival time of 30 starved 

 sisters each. 



D. The average survival time of the starved sisters of B from o to 12 hours 

 and of C from 12 to and including 25 hours. 



E. Differences between average survival time given in rows B and D, and 

 between C and D. 



capillary pipette and placed in tap water. As soon as they 

 separated one was placed in a watch glass of fresh yeast suspen- 

 sion, while the other was left in tap water. Sets of thirty each 

 of such pairs were killed in N/75 KCN at intervals of i, 2, 3, 4, 

 5, 6, 7, 8 and 9 hours. It was impossible to continue this experi- 

 ment longer than nine hours, for a large percentage of those which 

 were fed, divided between the ninth and tenth hour. Sets of 

 starved animals were continued however for 25 hours, being 

 killed at intervals of 12, 15, 19 and 25 hours. The results are 

 summarized in Table VI., and in the curves of Fig. 3. 



The difference in survival time shows a general increase up to 

 and including the ninth hour, the animals which were placed in 

 the yeast supsension living longer than their sisters which were 

 placed in clear tap water. The survival time of the latter showed 

 a marked decrease with age. The experiment was continued, 

 but instead of feeding one sister and starving the other, both 

 were starved, as was done with Didinia in experiment V. above. 

 Thirty pairs were left to starve in tap water for each period of 15, 

 19 and 25 hours, and then tested with KCN. I arbitrarily 



