PROTOZOA AND THE UTRICLES OF UTRICULARIA. 265 



The valve of the bladder is closed so tightly that nothing within 

 can escape. 



At present there is little doubt regarding the utilization by the 

 plant of material derived from the animals captured and digested. 

 Darwin concluded from a study of the quadrifid cells in the inner 

 walls of the bladders before and after the capture and dis- 

 integration of food that the plant absorbed nutriment derived 

 from the captured animals. Further evidence that this is true 

 is offered by Biisgen (1888) who measured fed and unfed plants 

 at intervals during a period of about three weeks. The fed 

 plants grew twice as fast as the unfed plants during this period, 

 apparently because of the nutriment supplied by the animals 

 captured and absorbed by the bladders of the latter. 



EXPERIMENTS WITH OTHER PROTOZOA. 



Although the principal experiments were carried out with 

 paramecia and euglenas a few other protozoa were used as 

 opportunity offered. These included representatives of all three 

 classes of the free-living Protozoa Sarcodina, Mastigophora and 

 Infusoria. 



Centropyxis aculeata is captured by bladders and starved to death. 

 Shells of specimens of this species were observed in bladders 

 brought into the laboratory, but these apparently contained no 

 living animals. Two experiments were performed to determine 

 the relations of this species to the plant. 



Experiment 37. Fifteen detached bladders were placed in a concavity in water 

 containing a number of large specimens of C. aculeata. Six days later 6 of these 

 bladders were found to be infected, 4 with one and 2 with 2 each. The shells 

 contained very little protoplasm approximately one tenth of the original amount- 

 but this was still alive and able to form pseudopodia. Apparently the conditions 

 in the bladder have no directly injurious effect upon these rhizopods but deprive 

 them of opportunities for capturing food and hence lead to their starvation. 



Experiment 27. Four bladders on one stem were inoculated, three with one 

 and one with 2 specimens of C. aculeata. Seven days later they were dissected 

 out and examined. Two shells were empty and the other three contained a very 

 small amount of living protoplasm. The former apparently were starved to death 

 and the latter were almost dead of starvation. 



Heteronema acus is captured but not injured by bladders. This 

 green flagellate was used in 2 experiments. 



Experiment 16. Four bladders, 2 on each of 2 stems were inoculated with 

 several specimens each. These bladders soon died and disintegrated but one of 

 them still contained active specimens 3 days later. 



