256 R. W. HEGNER. 



In tap water, 12 of 30 bladders captured 16 specimens; 10 of 30 bladders captured 

 12; 26 of 66 captured 31; and 6 of 30 captured 8, respectively. Totals: 5401156 

 bladders captured 67 specimens; 35 per cent, of the bladders captured an average 

 of 1.3 specimens per bladder. 



From these results tap water seems to be a more effective 

 medium for the capture of paramecia than hay infusion; 44 

 per cent, or 121 of 276 bladders captured 344 or 2.8 per bladder 

 in tap water, whereas only 28 per cent, or 73 of 260 bladders 

 captured 1.5 per bladder in hay infusion. The other media 

 used were not sufficiently studied to give significant results, but 

 saline solution is apparently disadvantageous, and beef meal 

 solution and malted milk solution are as favorable as hay infusion 

 or even more favorable, but not as effective as tap water. Obser- 

 vations of the activities of the paramecia in different media 

 revealed the fact that the organisms swam about more rapidly 

 in tap water than in any other medium. This means that in 

 tap water the chances that paramecia will come in contact with 

 the valves of the bladders more frequently and with more force 

 are greater than in the other media and would lead to a larger 

 number being captured in a given period. The conclusion based 

 on these experiments is therefore that the differences in the 

 number of specimens captured are due to the effects of the 

 media on the rate of speed of the paramecia rather than their 

 effect on the bladders. 



Paramecia are killed by bladders, on the average, in a period of 

 about 75 minutes. That paramecia die after being captured by 

 utricularia bladders was proven by Exp. I described above. 

 Considerable effort was made to determine the exact length of 

 time required to bring about their death. Data from two types 

 of experiments are available. In 16 experiments stems bearing 

 bladders were placed in cultures containing paramecia and 

 removed usually at the end of 2 hours but sometimes in one hour 

 or in 4 hours. An immediate examination provided data re- 

 garding the number captured during this period and the numbers 

 that had been killed or were still alive. The total number 

 captured in these 16 experiments was 780 of which 563 were 

 dead and 217 were alive when the bladders were examined. 

 A summarv of the data is as follows: 



