574 ASA A. SCHAEFFER 



not react definitely toward egg white. Its stimulating quali- 

 ties are considerably weaker than those of carmine. It also 

 probably ranks below uric acid in this respect. 



SUMMARY 



1. Experiments upon the feeding behavior of ameba may read- 

 ily be made. The method of investigation consisted in laying a 

 •particle of some substance in the ameba's probable path, and 

 then making camera lucida drawings of the outlines of the ameba, 

 at short intervals, as long as the particle was thought to influence 

 the behavior. Time records were also kept. 



2. Two kinds of amebas were tested. One kind was full of 

 granules, formed few pseudopods, and was relatively slow in its 

 movements. The other type contained but few granules in its 

 body, formed many pseudopods, moved actively and ate vora- 

 ciously. The granular amebas ate carmine readily and retained 

 it for only a few minutes, while the raptorial amebas refused 

 carmine frequently, but when eaten it was retained usually for 

 hours. 



3. Ordinary daylight, acting continuously, has no appreciable 

 effect on feeding. 



4. Ameba feeds by means of food cups which may be of very 

 variable size and construction depending upon the character of 

 the object to be eaten, upon the general degree of hunger of the 

 ameba, upon the shape and position of the ameba with respect 

 to the stimuli, and so on. The shape and size of the food cup 

 cannot be predicted from the character of the stimulating object 

 alone. 



5. Movement of an object is a very important factor in deter- 

 mining whether or not it shall be eaten. 



6. Food cups with considerable quantities of water in them are 

 usually formed only over moving animals; dead animals or parts 

 of animals are surrounded by food cups only very slightly larger 

 than these objects themselves. 



Carmine is readily eaten by ameba although it possesses no 

 food value. A hungry ameba will eat the same carmine grain 



