THE ANIMAL KINGDOM 



373 



There is no mouth through which food passes into the interior 

 of the animal. Food is obtained by means of the pseudopodia, 

 the method used varying with the type of food. In securing 

 nonmotile food such as certain plants (desmids) and encysted 

 protozoans, the pseudopodia surround the object in a tight 

 embrace and gradually engulf it. In attacking a larger object 

 such as a mass of bacterial glea, two pseudopodia surround a 

 portion of the mass and gradually pinch it off. As a rule 

 rapidly moving objects cannot be captured, though motile 

 Protozoa such as Paramecium or Chilomonas (Fig. 207) may 

 be secured when they are relatively quiet. Thus a Paramecium 



Fig. 207. — Amoeba proleus capturing Chilomonas para, another protozoan, by 

 means of its pseudopodia. Sketched at successive stages. (After Kepner and 

 Taliaferro, Biol. Bull.) 



may be cornered by an amoeba against a solid object and 

 trapped in a pocket formed by two pseudopodia, or the amoeba 

 may send pseudopodia about the Paramecium and confine it to 

 an enclosed space before disturbing it. Sometimes the amoeba 

 advances upon a Paramecium and holds it fast by gripping it 

 with the ends of the pseudopodia, after which a portion of the 

 prey is "bitten" off (Fig. 208). Smaller objects are engulfed 

 entirely. Within the body of the amoeba the food is broken 

 up into small particles and digested in the food vacuoles. 

 Undigested remains are cast out through the body wall. It 

 may be inferred from this that the taking of food is not a 

 haphazard process, for the amoeba does not engulf everything 

 that it happens to meet; this means that it is capable of dis- 

 tinguishing between food and inedible objects. 



