PROTOZOA AND THE UTRICLES OF UTRICULARIA. 255 



Time required for detached bladders to capture paramecia, from 8 minutes to 2 



hours; average, 59 minutes. 



Number captured per positive attached bladders, from one to 6; average, I-54- 

 Number captured per positive detached bladder, from one to 4; average, 1.56. 



These data indicate that no difference exists between attached 

 and detached bladders so far as the capture of paramecia is 

 concerned. Regarding the length of time required for the 

 capture of paramecia the data are not accurate since the bladders 

 could not be kept under continuous observation; but in a culture 

 containing active paramecia about 30 per cent, of the bladders 

 succeeded in capturing one or more paramecia within one hour. 



The number of paramecia captured depends on the character of 

 the culture medium. Six experiments were carried out to test 

 the effects of different culture media on the capture of paramecia. 

 It was thought that the bladders might be stimulated to greater 

 activity by media containing nutrient materials. The con- 

 trasting media used in these experiments were as follows (in 

 every case the number of paramecia in the medium was increased 

 by centrifuging the hay infusion, and the bladders were attached 

 to branches of the plant) : Exp. 29, spring water v.s. hay infusion ; 

 Exp. 38, tap water v.s. hay infusion v.s. beef meal v.s. malted 

 milk v.s. 0.7% saline; and Exp. 41, 42, 44 and 46, hay infusion 

 v.s. tap water after washing in tap water. 



Experiment 20. In hay infusion, 20 of 69 bladders, or 29 per cent., captured 35 

 specimens in a period of 2 hours; the number per positive bladder ranged from one 

 to 86, and the average per positive bladder was 1.75. In spring water, 62 of 73 

 bladders, or 85 per cent., captured 272 specimens in the same period; number per 

 positive bladder, one to 19; average, 4.40. 



Experiment 38. In hay infusion, 13 of 40 bladders, or 32 per cent., captured 23 

 specimens or 1.8 per positive bladder. 



In tap water, 5 of 47 bladders, or n per cent., captured 5 specimens or I per 

 positive bladder. 



In 0.5 per cent, beef meal solution, 17 of 44 bladders, or 39 per cent, captured 

 21 specimens or 1.2 per positive bladder. 



In i.o per cent, malted milk solution, 16 of 44 bladders, or 36 per cent., captured 

 27 specimens or 1.7 per positive bladder. 



In 0.7 per cent, saline solution, 2 of 43 bladders, or 5 per cent., captured 2 

 specimens or i.o per positive bladder. 



Experiments 4146. In hay infusion, 9 of 30 bladders captured 10 specimens; 

 4 of 30 captured 4; 19 of 61 captured 24; and 8 of 30 captured 10, respectively. 

 Totals: 40 of 151 bladders captured 48 specimens; 26 per cent, of the bladders 

 captured an average of 1.2 specimens per bladder. 



