34 



COLLEGE ZOOLOGY 





Figure 12. Amoeba. Ingestion of food. A, successive positions of a pseudopodium of an 

 amoeba capturing a flagellate, Chilomonas. B, ingesting a cyst of a flagellate. C, ingesting a plant 

 filament. D, a food cup for ingesting a flagellate superimposed on a food cup containing a 

 ciliate. (A after Kepner and Taliaferro; B after Jennings; C after Rhumbler; D after Becker.) 



formed and the victim is enclosed without 

 being touched; in this manner a dozen or 

 more flagellates may be ingested in one 

 food cup. A small amount of water is taken 

 in with the food, so that a vacuole is formed 

 with walls which were formerly part of 

 the cell membrane on the outside of the 

 body, and contents consisting of a parti- 

 cle of nutritive material suspended in water. 

 The whole process of food taking occupies 



one or more minutes, depending on the 

 character of the food and the temperature. 

 It increases in rapidity up to 25° C, and 

 decreases to zero at about 33° C. The 

 amoeba is not always successful in accom- 

 plishing what it undertakes, but when it does 

 not capture its prey at once, it seems to show 

 a persistence usually attributed only to 

 higher organisms (Fig. 13). 



Feeding occurs only when the amoebas 



/•-Carbon M 



v^Food ^ 



Amoeba encounters 

 food and carbon 

 particle 



2J^ minutes 

 later a food 

 cup is formed 



7^ minutes 

 later 



(The carbon is not ingested) 



8 minutes 

 later 



Figure 13. Amoeba proteus exhibiting food selection. The arrows indicate the direction of the 

 movement of the protoplasm in the pseudopodia. (After Schaeffer.) 



