Selection of I' 00(1 lu Stciitor Cceruleus (Ehr.) I 31 



reversal of the cilia; others are carried to the mouth and ingested. 

 Of two particles within the funnel at the same time one mav be 

 thus rejected while the other is ingested. Selection thus occurs 

 not only from among particles reaching the pouch successively, 

 but from a large number reaching the pouch at once. 



2 Stentor discriminates very accurately between organisms 

 (Phacus, Euglena, etc.) and indigestible particles (carmine, glass, 

 sulphur, starch, etc.), ingesting the former and rejecting the latter. 



3 Stentor discriminates between different kinds of organisms, 

 eating some (Euglena, Phacus triqueter) with great readiness, 

 while others (Trachelomonas hispida, Phacus longicaudus) are 

 rarely ingested. 



4 States of hunger and satiety, and intermediate conditions, 

 are shown to exist in Stentor by differences in the behavior toward 

 food. The animal discriminates more perfectly (i. e., more 

 restrictively), when almost satiated than when very hungry. 

 When very hungry it may ingest many indigestible particles (car- 

 mine, india ink, etc.) 



5 The amount of a given substance ingested depends upon 

 what other substances are present. Stentor in water containing 

 indigestible particles, such as carmine, may ingest much of the 

 latter; if the water contains in addition many organisms fit for 

 tood, very little of the indigestible matter is ingested. 



6 It was not found that Stentor and paramecium become 

 lastingly "educated" to reject certain sorts of food that they have 

 formerly taken. Such changes as occur in selection seem to be 

 mainlv matters of hunger and satiety. 



7 Stentor selects its food upon a tactual basis and apparently 

 not upon a chemical one. That is, Stentor reacts in selecting 

 food, to ph\sical properties only or chiefl) , and not to chemical 

 properties. 



8 Stentor in a condition of satiety differs in many respects 

 from Stentor in a condition of hunger. In satiety we find the 

 following conditions: a. Extension is always submaximal. b. 

 The aboral side is more strongly convex than the oral side. c. 

 There is a marked decrease in the activity of the membranellae. 

 d. Stentors respond much more readily to mechanical stimulation 



