88 Asa Arthur Schaeffer 



spiral turning or revolving on the long axis. The Stentors swam 

 in a circle as one would expect from a consideration of the cres- 

 centic shape of the partly extended Stentor. This method of 

 behavior also resulted in the ingestion of but very few particles. 



These are probably the chief constituen ts of what may be called 

 the normal behavior of Stentor. We shall next consider the ex- 

 periments which were designed to answer the question: Can 

 Stentor discriminate between food and indigestible particles? 



EXPERIMENTS WITH SPECIFIC PARTICLES 



We have just seen that the normal behavior of Stentor is very 

 complex for an organism of such simple anatomy, especially as far 

 as the movements and action of the cilia are concerned. We saw 

 that there are at least four distinct groups of cilia — five, if the 

 pouch and funnel cilia are considered as two groups — each of which 

 has a more or less definite thing to do under ordinary circum- 

 stances; but the moment that conditions obtain which are unusual, 

 the behavior of one or more of these systems of cilia changes. We 

 saw that any one of these four or five groups of cilia can change 

 its behavior while the rest of the ciliary apparatus beat in the 

 usual manner; or all the cilia of the entire Stentor can change direc- 

 tion and force of beat upon occasion so that entirely changed 

 behavior results. In fact with these four or five groups of cilia 

 which may beat independently of each other and vary their be- 

 havior in different ways, it seems hardly possible that a situa- 

 tion could confront a Stentor which could not satisfactorily be 

 met by having recourse to the many possibilities of the varying 

 behavior of these ciliary systems. The next problem then was to 

 devise an experiment that should test the efficiency of this highly 

 adaptive ciliarv apparatus in discriminating between food and 

 indigestible particles. 



Experiment I . Discrimination between Phaciis and Sulphur 



For this purpose roll sulphur was ground up into a fine powder 

 and then thoroughly stirred with a large quantity of water. After 



