REACTIONS OF AMEBA TO PROTEINS 77 



behind, A grain of globulin was then promptly ingested. An- 

 other grain of keratin was then laid in the ameba's path (657). 

 The ameba flowed into contact with it and ingested it by slowly 

 flowing around it. The ameba became comparatively quiet for 

 a few minutes. The keratin was then excreted but at once re- 

 ingested (677). Within a minute and a half after reingestion it 

 was again excreted and left behind. A new piece of keratin which 

 the ameba encountered (679) as the previous piece was excreted, 

 was avoided, although a small pseudopod was sent out toward 

 it. Another new piece of keratin was placed in the ameba's 

 path (682). The ameba moved toward it slowly, then encircled 

 it almost completely and finally moved off. The ameba had 

 not come into contact with the keratin. This is one of the best 

 instances on record of the encircling of an object by an ameba 

 without coming into contact with it. This phenomenon is of the 

 greatest interest but discussion of it must be deferred until later. 



A piece of keratin was placed in the path of a slow moving 

 raptorial ameba (951). The ameba moved almost into contact 

 with the keratin, then turned toward the left and moved on. 

 The keratin was shifted but it was again avoided (957). The 

 same piece of keratin was again placed before the ameba (960). 

 The ameba moved on over the keratin without any definite reac- 

 tion toward it. A fresh piece of keratin was next laid in the 

 path of the ameba (965). The ameba moved into contact with 

 the keratin and formed an imperfect food cup in which the kera- 

 tin was ingested. Two hours later the keratin was still present 

 in the ameba's body. 



The general behavior of ameba toward keratin is very similar 

 to that of ovalbumin. On account of the paucity of experiments 

 no accurate comparisons may be made, but in a general way it 

 may be said that keratin and ovalbumin seem to stimulate ame- 

 bas with about equal intensity. The fact that a raptorial ameba 

 retained a keratin grain for over two hours recalls similar results 

 with carmine. Raptorial amebas are much more apt than the 

 granular to retain what they ingest, whether the ingested sub- 

 stance is of food value or not. It may be of little significance 

 therefore that keratin was retained for hours after ingestion by a 



