68 A. A. SCHAEFFER 



The causes determining the behavior in figures 1878 to 1886 are 

 not entirely clear. It is possible that when the gluten was partly 

 exposed (1879 to 1881) the motion of the ameba caused the free 

 surface of the gluten to come into contact with other parts of 

 the ameba, giving thus the effect of movement of the gluten and 

 producing therefore an efficient food stimulus. For this ameba, 

 gluten lost its stimulating food properties as soon as it was sur- 

 rounded by a food cup; but when the food cup was withdrawn 

 and the gluten was again exposed, it recovered its stimulating 

 qualities. Although a motionless object may be ingested, it will 

 not remain ingested as a rule unless either the object for some 

 cause moves about for a short while or another moving subject 

 is eaten soon thereafter. 



Summary of behavior toward grain gluten 



In general, the grain gluten used in the foregoing experiments 

 calls forth reactions that are very similar to those produced by 

 globuhn, excepting that globulin is somewhat more attractive 

 than gluten. 



Gluten is an actual food substance which undergoes digestion 

 in the ameba's body considerably more rapidly than globulin, as 

 is indicated in figures 532 and 534. 



Granular amebas eat gluten more readily than the raptorial; 

 the latter seldom completely ingest solid dead bodies of any sort, 

 and gluten forms no exception. As a rule the eating process 

 goes on normally until the gluten is almost surrounded with pro- 

 toplasm. Streaming then begins in some other part of the ameba, 

 usually in the vestige of a previous pseudopod, and the ameba 

 then moves off leaving the gluten behind. This break in the 

 ingesting process seems to be due to the lack of stimulation such 

 as is produced by movement of the food object. Apparently it 

 requires stronger (or different) stimuU to bring about this last 

 stage in feeding than any other, for if the object is once com- 

 pletely surrounded by protoplasm and the edges of the proto- 

 plasmic covering sheet have fused, it is almost invariably re- 

 tained and digested, if of food value. That the lack of requisite 

 stimulation to complete ingestion proceeds from lack of move- 



