Selection of Food in Stentor Ccerideus (Ehr.) lOQ 



a particle that is to be ingested. The nature of the assumed re- 

 jecting and ingesting mechanism and the way selection is brought 

 about, will be discussed later on. 



We have thus far dealt mainly with what may be called stages 

 of moderate hunger and moderate satiety. There still remain the 

 states of utter hunger and of surfeit to be described. 



The condition of extrem.e hunger may be produced by putting 

 a number of Stentors with as little of their culture solution as pos- 

 sible into clear tap-water and keeping the water as free from bac- 

 teria as possible. There is no evident difference in behavior 

 between Stentors in the condition of extreme hunger and those 

 moderately hungry. 



The condition of utter satiety is more interesting. The behav- 

 ior of a Stentor in such a state is very different from the normal 

 behavior. The following experiment fully illustrates this. Sev- 

 eral hundred small paramecia were placed with a few Stentors 

 in a watch glass for two days, so that the Stentors could feed upon 

 them. The largest of the several Stentors was then selected for 

 feeding with Trachelomonas hispida. The Stentor was filled 

 with a number of globular masses of slightly brownish transparent 

 material which probably represented as many broken down para- 

 mecia. The Trachelomonas were fed from a capillary pipette 

 as usual. Following are the results. 



Experiment ii. The Effect of Utter Satiety on Stentor 



In this experiment the figures, i to 24, signify as many Trach- 

 elomonas hispida which were fed to Stentor. As in preceding 

 experiments, they are numbered in the order in which they were 

 fed. Stage "pipette presented," means that the end of the cap- 

 illary pipette which contained Trachelomonas hispida was brought 

 within about half a millimeter from the animal's disk, and that a 

 very slow stream of water was then caused to flow against the 

 disk. All the other stages of behavior are self-explanatory. 



