PROTOZOA AND THK UTRICLKS OF UTRICUL ARIA . 253 



results suggest that the euglenas found in bladders in nature are 

 free-living species that were captured by the bladders and were 

 unable to escape and that these euglenas are either able to with- 

 stand any digestive ferments contained in the bladders or do 

 not stimulate the production of such ferments by the bladder 

 cells. 



Euglenas are not injured in bladders that have captured and killed 

 paramecia. 



Experiment 30. Thirty-nine bladders attached to 4 stems were immersed in a 

 euglena culture for three hours and then in a paramecium culture for one hour. 

 Seventeen of the bladders became infected with paramecia, from one to 17 in each 

 bladder, the average per bladder being 3.6. Four of the bladders became infected 

 with one paramecia each and three of these also contained euglenas, one with 5 

 and 2 with 2 each. In every case the paramecia had been killed but the euglenas 

 were active. 



Experiment 33. Seventeen bladders attached to 2 stems were immersed in a 

 paramecium culture for 2\ hours; 13 became infected with paramecium as follows: 

 5 with one each, 5 with 2, one with 4, one with 6, and one with 8. After an interval 

 of 4 hours when all the paramecia had been killed and many had already dis- 

 integrated euglenas were injected with a capillary pipette into each of the infected 

 bladders. Nineteen hours later the euglenas within these bladders were active 

 and apparently normal. 



Experiment 51. -Forty-four bladders attached to 6 stems were immersed in a 

 mixed culture of paramecia and euglenas and allowed to remain for 3 hours. 

 Twenty-one bladders became infected with paramecia as follows: 18 with one each, 

 2 with 2, and one with 3; twenty-nine bladders became infected with euglenas; 

 and 14 became infected with both. These bladders were examined daily during 

 the four succeeding days and active euglenas were observed in 13 of the 14 bladders 

 that captured paramecia. In the i4th bladder the euglenas were not moving. 

 The euglenas were active in 14 of the bladders that had not captured paramecia 

 and quiet in the isth. Seven bladders captured paramecia but no euglenas and 6 

 bladders did not become infected with either. 



Experiment 50. -In this experiment, which was initiated for another purpose, 

 one bladder was found to contain active euglenas in the presence of disintegrating 

 paramecia. 



In the above experiments paramecia and euglenas became 

 associated within the bladders of Utricularia in three different 

 ways: (i) bladders were first infected with euglenas and then 

 with paramecia, (2) bladders were first infected with paramecia 

 and then euglenas were injected into them, and (3) bladders 

 became infected with both in a mixed culture of paramecia and 

 euglenas. The results show that regardless of the method of 

 infection the euglenas remain active in bladders that have brought 



18 



