BEHAVIOR OF AMEBA TOWARDS VARIOUS SUBSTANCES. 313 



Hematin is not toxic to the ameba; when eaten with food 

 materials it may remain in the ameba for many hours without 

 producing any ill effect. 



Indigotin. Merck's reagent, indigo blue. To the left of the 

 path of a granular ameba was placed a grain of indigotin 278. 

 The ameba moved forward until the tip of the main pseudopod 

 was past the test object 279. A pseudopod was then sent out 

 to the left, which moved into contact with it 280, 281. As the 

 ameba moved forward, it moved out of contact with the indigotin. 

 A small pseudopod which was sent out into contact with the 

 indigotin from the mid-region of the ameba 283 remained in 

 contact with the test substance for a few minutes while the ameba 

 moved on, but it was finally pulled away. 



Ameba reacts more decidedly positively to indigotin than to 

 hematin, glass, or carbon. In no case however was ingestion 

 attempted. 



Cholesterin. Eimer and Amend's. In the path of an active 

 granular ameba with many pseudopods, was placed a grain of 

 cholesterin 35. As the ameba moved forward two pseudopods 

 were sent out toward the cholesterin 37 but only one of them 

 came into contact with it. The ameba moved off through a 

 pseudopod thrown out on the right, leaving the cholesterin 

 behind. 



As far as my experiments go, it appears that cholesterin 

 belongs in the same class as carbon, glass, etc. No attempt at 

 ingestion is made. Cholesterin is sensed at a distance of at least 

 fifty microns. 



Starch Grains from Arrowroot. Taylor's Commercial. A grain 

 of arrowroot starch was placed in the path of a three-pronged 

 raptorial ameba 288. The ameba moved forward through the 

 middle pseudopod directly into contact with the starch grain 

 and then passed on, on the right, after forming and retracting 

 two pseudopods on the left. The ameba then happened to 

 move toward another mass of arrowroot starch 294. When 

 the ameba came within about thirty microns of the starch, it 

 withdrew from the starch and moved forward to the right 

 296 but the pseudopod lying nearer the starch became the 

 main pseudopod 297. When the tip of the main pseudopod 



