PROTOZOA AND THK UTRICLES OF UTRICULARIA. 257 



g of 21 or 43 per rent, were dead one hour after the beginning of the experiments. 



12 of 21 or 57 per cent, were alive one hour after the beginning of the experiments. 



416 of 603 or 69 per cent, were dead two hours after the beginning of the experi- 

 ments. 



187 of 603 or 31 per cent, were alive two hours after the beginning of the experi- 

 ments. 



138 of 156 or 88 per cent, were dead four hours after the beginning of the experi- 

 ments. 



18 of 156 or 12 per cent, were alive four hours after the beginning of the experi- 

 ments. 



These data show that the percentage of paramecia killed 

 increases from 43 one hour after the beginning of the experiments 

 to 88 four hours after the beginning of the experiments. The 

 exact length of time necessary to kill these protozoa could not 

 of course be determined in this way. 



Three other experiments were carried out in the following 

 manner. Branches bearing bladders were immersed in a para- 

 mecium culture for a short period, then washed, placed under a 

 large cover glass in a petri dish and flooded with water. Exami- 

 nations of these preparations were made at frequent intervals. 



Experiment 50. A record of 9 captured paramecia shows one dead in 45 

 minutes; 2 active at least 42 minutes but dead in 56 minutes; one alive 49 min., 

 but dead in 61 min.; one alive 54 min., but dead in 72 min.; one alive 64 min., 

 but dead in 73 min.; one alive 75 min., but dead in 91 min.; one alive 84 min., 

 but dead in 103 min.; one alive 104 min., but dead in 114 min. The average period 

 during which these paramecia continued to live was 64 minutes and the average 

 time until their death was 75 minutes. 



Experiment 53. In this experiment a record was kept of 23 captured paramecia. 

 The period that these remained active after capture ranged from 20 to 127 minutes, 

 with an average of 48 minutes, and the period until their death ranged from 34 

 to 141 minutes or an average of 72 minutes. 



Experiment 54. A record was made of 62 specimens in this experiment. Two 

 were active 20 minutes; 3 from 30 to 40 min.; 5 from 40 to 50; 9 from 50 to 60; 

 15 from 60 to 70; 3 from 70 to 80; 9 from 80 to 90; 4 from 90 to 100; 3 from 100 

 to no; and 9 from 113 to 170. Two were dead in from 20 to 30 minutes; 2 from 

 40 to 50 min.; 5 from 50 to 60; 7 from 60 to 70; 15 from 70 to 80; 5 from 80 to 90; 

 7 from 90 to 100; 2 from 100 to no; 5 from no to 120; and 10 from 123 to 180. 

 The active period of the greatest number of specimens was from 50 to 80 minutes, 

 35 of the 62 falling within this range. The average active period was 78 minutes. 

 The death period of most of the specimens was from 50 to 98 minutes, 39 of the 62 

 falling within this range. The average death period was 93 minutes. 



The average active period of the paramecia studied in Exps. 50, 

 53 and 54 was 64 minutes for 9 specimens; 48 minutes for 23; 

 and 78 minutes for 62. If the data of these three experiments 



