Selection of Food in Stentor Cceruleus [Ehr.) 121 



mecia, Euglenae, and carmine; 3 others, paramecia, Euglenae, and 

 india ink. 



. One hour after these experiments were set up all the glasses were 

 examined. All the Stentors which were placed in ink or carmine 

 mixtures, whether paramecia were present or not, contained ink 

 or carmine but the amounts were variable. More carmine was 

 found in the Stentors than ink. Likewise all the paramecia placed 

 in ink or carmine mixtures contained vacuoles of these substances. 

 The highest number of vacuoles was from 40 to 50. The lowest 

 number observed was 4. More ink than carmine was found n 

 paramecia. 



All the glasses were examined once a day after they were set 

 up. Three days after the experiment was begun, some paramecia 

 were found with very few vacuoles of carmine. The smallest 

 number was 4. These paramecia were then placed in fresh car- 

 mine, and in half an hour they contained 50 or more vacuoles 

 each. The carmine and ink content of the Stentors had so far 

 remained constant. Seven days after the experiment was set up, 

 no decrease in the number of vacuoles of ink or carmine in either 

 paramecia or Stentors was found. But one paramecium was 

 found with no carmine vacuoles. This paramecium was then 

 placed with fresh carmine and tor over an hour no carmine was 

 taken. It was then placed in fresh ink and in 30 minutes 6 vac- 

 uoles of ink were found to have been ingested. This result is 

 probably due to the fact that the grains of india ink are smaller 

 than the grains of carmine. 



Ten days after the experiment was set up many paramecia in 

 those glasses where the least ink and carmine happened to be, 

 contained very few vacuoles ot these substances, but upon adding 

 some fresh carmine or ink these paramecia at once filled up on 

 these substances as they had done in the beginning of the experi- 

 ment. The paramecia in the glasses where the carmine or ink was 

 dense contained about the same quantity of these substances as at 

 the start. About the same may be said for the Stentors. In the 

 glasses in which the ink or carmine was dense the Stentors were 

 filled with these substances. In other glasses the Stentors con- 

 tained very httle ink or carmine; but upon refilling, these sub- 

 stances were again taken up as at the beginning of the experiment. 



