THE PROTOZOA OR THE SIMPLEST ANIMALS 



animated jelly, with no constant form. The outer part 

 of its body, the ectoplasm, is clearer and firmer than the 

 inner part, or endo plasm, which is granular and more fluid. 

 There is a single nucleus and a contractile vacuole. 

 Amoeba flows around its food and takes it into its endo- 

 plasm where it is digested in food vacuoles. Multiplication 

 is commonly by fission, although after surrounding itself 



FIG. 120. Amoeba proteus. A, active state; cv, contractile vacuole; 

 n, nucleus; p, pseudopod; B, Amoeba dividing; C, cyst; 1-4, stages in 

 ingesting a particle of food, F. 



with a cyst Amoeba may divide up into minute bodies 

 called spores, which ultimately break out and become small 

 Amoebae. 



The common Amoeba is generally found in fresh waters 

 and usually appears in cultures such as those used to ob- 

 tain Paramcecium. There are several kinds of Amoeba, 

 a few of which are parasitic in the bodies of animals. 

 Certain inflammatory diseases of the human intestine 

 (amoebic dysentery) have been traced to Amcebas and re- 

 lated organisms. Many forms allied to Amoeba live within 

 a shell which is formed either by secretion or by the ag- 



