AMOEBA OF CLASS SARCODINA 



87 



phenomena are the same as those found in the highest forms of life 

 but reduced to very simple terms. Here we may study the entire 

 metabolic cycle in progress within the confines of a single cell. Its 

 phases are as follows: 



Food. — Its prey consists chiefly of smaller Protozoa, small single- 

 celled plants, such as diatoms and desmids, and portions of filamen- 

 tous algae. Bacteria may be used to some extent and rotifers (small 

 Metazoa) are sometimes devoured. 



Ing-estion. — Amoeba has no definite mouth but the food is taken 

 into the body by engulfing it at any point that comes in contact 

 with it. A pseudopodium is formed at this point, and the end of it 

 flows around the food particle until the particle is entirely enclosed. 

 A droplet of water is included with the food to form what is called 

 a food vacuole. These vacuoles move about in the endoplasm. 



E^ejfion 



xcretion 



Fig. 34. — Diagram to show the phases of the metabolic process as it occurs 

 in amoeba. (Redrawn by permission from Wolcott, Anional Biology, published 

 by McGraw-Hill Book Company.) 



Digestion. — The food gradually disintegrates and much of it goes 

 into solution in the fluid of the vacuole. The function of digestion 

 is to convert complex materials into a soluble, absorbable form. It 

 is assumed that the surrounding cytoplasm secretes enzymes into 

 the food vacuoles of Amoeba to perform this function, since enzymes 

 serve this purpose in larger animals where exact study can be made 

 on the process. A circulatory system is not necessary since the 



