CHOICE OF FOOD IN AMEBA 



A. A. SCHAEFFER 



Zoological Laboratory, University of Tennessee 



CONTENTS 



PAGE 



Introduction 220 



Reactions to two particles of different constitution lying close together 220 



The effect of mechanical stimulation 226 



Discussion of experimental results 231 



Choice of food 231 



Selection of food in stentor and Paramecium as compared with that in ameba. . 246 



Summary 250 



Bibliography 251 



Explanation of plates 252 



INTRODUCTION 



In a previous paper ('16a) I outlined the problem of choice 

 of food among animals as I conceive it, and in this paper I wish 

 to discuss the power of choice in ameba as exhibited in the 

 various series of experiments recorded in several of my previous 

 papers, as well as in experiments which are recorded for the first 

 time in this paper. 



The problem of choice of food has turned out to be very 

 intricate and difficult; much more so than was at first suspected. 

 It is rendered especially difficult because previous experience in 

 sense perception plays a very important part in selection. Choice 

 thus becomes in large part a developing or historical process. 

 Series of individual acts of choice are the smallest units which 

 can be considered in analyzing this problem. Individual acts 

 of choice are frequently quite meaningless, and even contra- 

 dictory to each other, when removed from their historical set- 

 ting. This fact is of the greatest importance in this connection 

 and must not be lost sight of. 



Before a discussion of choice of food is entered upon, I wish 

 first to describe two series of experiments which have particular 

 bearing on this matter. One series has to do with choice expressed 

 by an ameba when encountering two particles of different compo- 

 sition lying very close together, while the other series deals with 

 the effect of mechanically agitating various kinds of particles 

 in close proximity to the ameba. 



220 



