CHOICE OF FOOD IN AMEBA 225 



each other, the carbon lying in the anterior half and the globulin 

 in the posterior half — 178. The ameba then moved off in the 

 direction opposite to the original, but so that the carbon should 

 at once occupy a position at the posterior end. A few minutes 

 later the carbon was excreted. Ten minutes after the ameba 

 had enclosed the carbon and the globulin in the food cup, another 

 normal food cup was formed while the ameba was lying quiet, 

 but there was no solid substance in it, nor was there anything 

 in the vicinity to cause its formation. The stimulus producing 

 it must have been internal. 



This is a remarkable series of experiments. A degree of pre- 

 cision in food discrimination is disclosed in these observations 

 which was altogether unsuspected. The separating process in 

 the first two experiments is not understood. Not all the details 

 necessary to an understanding of the process were observed. 

 The ameba reacted like a higher animal might if reduced to 

 ameboid form. The last experiment clearly indicates that the 

 ameba was ' aware ' of the presence of a particle that was 

 not food lying close to one that was food. The way in which 

 the first food cup was formed clearly shows this. The long 

 delayed fusion of the free edges of the food cup indicates the 

 effect of the disturbing carbon. The long rest of thirty minutes 

 also is unusual. The change in the direction of locomotion was 

 doubtless caused by the position of the carbon. And the for- 

 mation of the empty food cup during the resting period was in 

 some way incited by the disturbing carbon, but just what con- 

 nection there might be between the two remains unknown. 



Gluten and glass. — In the path of an A. dubia that had just 

 previously ingested pieces of agitated glass, was placed a piece 

 of glass and a piece of gluten lying close together — -179. The 

 ameba moved into contact with the gluten and the glass — - 

 184-186 — and then carried them up on its back, but there was 

 no attempt to ingest either of the substances. 



Globulin and Coleps hirtus. — A small mass of metallic iron was 

 temporarily attached to a grain of globulin and slightly agi- 

 tated with an electric coil. The Amoeba dubia near which the 

 globulin lay, nevertheless treated it with indifference. A coleps 

 then came along, and while hovering over the globulin, both 

 the globulin and the coleps were ingested by the ameba in a food 

 cup thrown out from the posterior end — 190. Five minutes after 



