ON THE FEEDING HABITS OF AMEBA 573 



water had evaporated. The egg white was then broken up into 

 small granules and kept in a glass stoppered bottle. About a 

 year after it had been thus prepared it was used in these experi- 

 ments. The egg white swelled up and softened in water, but it 

 was only slightly soluble. 



In only a very few cases was egg white of this sort eaten. One 

 such case is figured — 1378. In the path of an ameba which had 

 eaten a piece of aleuronat ten minutes before, was placed a grain 

 of the egg white. Before the ameba came into contact with the 

 test substance two preexisting pseudopods began forming them- 

 selves into a food cup. The egg white was eaten in a typical 

 manner and retained as a food mass is retained. This ameba 

 had also previously eaten a piece of cholesterin which had been 

 experimentally agitated, and which was carried around by the 

 ameba for at least ninety-two minutes. That the eating instinct 

 was strong, even exceptionally strong, is shown by later be- 

 havior where it tried to eat another ameba as large as itself. 

 This cannibalistic instinct is relatively rare among amebas. I 

 have noticed it only a few times in all my observations. The 

 behavior of this ameba shows, then, that egg white as above pre- 

 pared, is a very efficient stimulus for inducing the feeding re- 

 action among gluttonous amebas. 



But for amebas not in this condition egg white does not possess 

 stimuli strong enough, as a rule, to induce ingestion. Thus the 

 piece of egg white in figure 30 caused a negative reaction. This 

 piece of egg white was too large for the best results. The general 

 result of the second trial with egg white on the same ameba — 

 95 — was negative behavior. On the third trial with the same 

 piece of egg white, the general result was again negative be- 

 havior, but — 102 — there is some indication of a positive reaction. 

 The ameba ingested carmine and a flagellate, both before the 

 trials with egg white and after, showing that the ameba was nor- 

 mal and that carmine possessed stronger food qualities than egg 

 white. 



To summarize : Egg white as prepared above induces the feed- 

 ing reaction only in those exceptional amebas in which the feed- 

 ing process is easily set into operation. The average ameba does 



