FORMATION OF FOOD-CUPS IN AMCEBA INDUCED 



BY CHEMICALS. 



J. GRAHAM EDWARDS. 

 From the Zoological Laboratory, The Johns Hopkins University. 



Feeding reactions of Amoeba have been described by different 

 investigators and from various standpoints. Jennings (i), 

 Kepner and Taliaferro (3), Mast and Root (4) Schaeffer (5), and 

 Beers (6) have contributed valuable data concerning such 

 reactions. Jennings mentions in connection with the extension 

 of a pseudopod toward a food particle, that this should be 

 attributed partly to chemical stimulation. Mast and Root hold 

 that surface tension is probably an insignificant factor in the 

 process of feeding, and Scrueffer is of the opinion in this connection 

 that the presence alone of a substance in solution is not sufficient 

 to attract Awceba, or to cause ingestion, but that the substance 

 must be actively diffusing from a definitely localized region. 

 Kepner and Edwards (2) conclude that there is no hypothesis as 

 yet advanced to explain quantitatively the reaction involved in 

 the movement of Rhizopoda, which can be applied to Pelomyxas 

 movement around food-bodies. 



While locomotion and movements observed in feeding still 

 remain unexplained, the following observations of feeding 

 reactions induced by chemicals may further extend or limit this 

 problem. For feeding reactions quite comparable in every way 

 to those described by the investigators mentioned, occur without 

 the presence of food and in a homogeneous medium. There are 

 no visible stimuli. 



When amcebse are washed in three changes of distilled water 

 and immersed in certain chemically pure salt solutions, food-cups 

 are formed in the absence of solid particles which are comparable 

 to those observed in the process of ingesting food. These cups 

 are formed as follows: On the under surface of one or more 

 pseudopods a local expansion of the ectoplasm occurs accompanied 

 by an inflow of endoplasm. Immediately the marginal surl'.uv of 



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