550 ASA A. SCHAEFFER 



Comparatively few observations of this kind have been made 

 for the reason that they did not seem to throw much Ught on the 

 main problem of feeding; but sufficient attention was paid to the 

 way in which food is handled inside of the ameba to see that it 

 depends at least as much upon the condition and nature of the 

 ameba as upon the character of the food object. 



From this brief description of the usual feeding habits of the 

 ameba, it is evident that very great variation is to be expected, 

 that eating is not a stereotyped process, and that no safe conclu- 

 sions can be drawn from the observation of a few isolated cases. 

 The recording of a large number of experiments seems to be one 

 of the best methods of arriving at the truth in cases where the 

 coefficient of variation is high. 



We shall now discuss in some detail one or two typical illus- 

 trations of the behavior of amebas toward each test substance. 



EXPERIMENTAL RESULTS 

 Reactions of ameba to whole organisms aiid to parts of organisms 



Ameba is essentially a beast of prey. By far the largest por- 

 tion of its food consists of living moving organisms, both plant 

 and animal. In a general way it may be said that a hungry 

 ameba eats any organism it can get hold of. Protozoa of any 

 size ranging from a small flagellate such as chilomonas, to a 

 Paramecium; rotifers; small entomostraca; diatoms and desmids, 

 etc. ; all are eaten providing only that they move slowly enough 

 to allow of the formation of a food cup over them. Observa- 

 tions bearing upon the variety of organisms eaten by ameba have 

 been made and recorded by practically all investigators of this 

 animal, but especially numerous are such observations in the 

 writings of Leidy (79), Penard ('02), and Gibbs and Bellinger 

 ('08). 



Notwithstanding the wide range of diet, small flagellates such 

 as chilomonas appear to form the larger part of the food of gran- 

 ular amebas; while diatoms and desmids constitute the greater 

 part of the food of raptorial amebas. This does not indicate a 

 preference for these particular kinds of food ; it may be that these 



