160 



REPRESENTATIVE SINGLE-CELLED ANIMALS 



a cell in the body of a many-celled organism assimilates the food it 

 receives from the blood. 



The exact methods employed in the ingestion of food differ con- 

 siderably in different species of amoeba, and even in the same 

 species, according to the conditions. In general, the outer sur- 

 face of the cell flows around the prey, either as finger-like pseudo- 

 podia or by the formation of a cup-shaped depression in which the 







. !!ka:^^^?5s<'i .-■v-j 







>^iS;f^:>^ 



\ y 



Fig. 88. — Feeding habits of amoebas. 



A and B, ingesting motile prey like small flagellate by means of pseudopodia with forma- 

 tion of large food vacuole. C, ingesting non-motile prey like filamentous algae without 

 formation of food vacuole. D and E, "cornering" a paramoecium against a bit of debris. 

 F, G, and H, cutting a paramoecium into two pieces either by mechanical pressure or perhaps 

 by stimulating the paramoecium so that it cuts itself into two. 7, 1, 2, and 3, ingesting an 

 encysted protozoan. (A to /?, after Kepner, Taliaferro and Whitlock; F and H, after 

 Mast and Root.) 



prey is finally enclosed (Fig. 88). Thus the food, surrounded by 

 a drop of the external water, becomes included within the endo- 

 plasm, forming a food vacuole. The mechanics of the process are 

 usually such that a portion of the outer surface of the cell is folded 

 in, loses its connection with the surface, and becomes a part of 

 the endoplasm. The process varies somewhat, but such is the 



