Selection of Food i7i Stentor Ca;rideiis {Ehr.) ill 



Slowing of cilia 10 rejected with 4 loops 



Pipette removed 11 eaten 



Cilia normally active 12 (Coscinodiscus) eaten 

 Trachelomonas presented with glass 13 rejected with 8 loops 



rod 14 rejected with 4 loops 



5 rejected with 4 loops 15 rejected with 8 loops 

 Pipette presented 16 rejected with 5 loops 

 Slowing of cilia 17 rejected with 3 loops 

 Pipette removed 18 rejected with 3 loops 

 Cilia normally active 19 rejected with 9 loops 

 Pipette presented Stream very slow 20 rejected with 3 loops 



6 rejected with 3 loops 21 rejected with 4 loops 



7 eaten 22 rejected with 5 loops 



8 rejected with 4 loops 23 rejected with 7 loops 



9 rejected with 8 loops 24 rejected with 2 loops 



This Stentor was at no time as fully extended as the average 

 Stentor is when not containing much food, nor was the cihary 

 action quite so strong and vigorous as when normally hungry. 

 This experiment is a good example of a remarkable change in the 

 physiologic state of Stentor in that the Stentor was slowly brought 

 from a condition of surfeit to one of only partial satiety. The 

 change was a gradual one inasmuch as five Trachelomonas im- 

 pinged upon the disk before the change was complete. A single 

 Trachelomonas caused apparently no visible change in behavior. 

 There seems to have been required the summated stimuli from 

 five Trachelomonas before the state of surfeit could be changed 

 to one of only partial satiety. 



There was also a gradual decrease in irritability arising from 

 the stream of water from the pipette. At first this caused contrac- 

 tion. A little later only a slowing of cilia occurred — the initial 

 stage of contraction. Still later the Stentor bent away from the 

 source of the stimulus, and finally the stream from the pipette 

 no longer caused any visible reaction. 



This decrease in irritability^ is parallel with the decrease in 

 satiety but is probably not due to the same cause. The cause of 

 the decrease was probably the frequent repetition of the stimulus, 

 the faint stream of water from the pipette, for a marked decrease 

 in irritability resulted before the glass rod was used. But the 



