86 



ONE-CELLED ANIMALS— PHYLUM PROTOZOA 



through this weak spot, and a pseudopodium is formed. As this proto- 

 plasm spreads out at the tip of the pseudopodium it assumes more of the 

 gel consistency, for it now forms the outer portion of the protoplasm. 



MtMIBiaii MH W HH WM M 



Pseudopodium 



Nucleus 



Con+rac+ile 

 vacuole 



Photo by Winchester 



Ectoplasm 

 Endoplasm 



■ — Plasma 

 membrane 



Food 

 Vacuole 



Fig. 7.1. Amoeba proteus. Top: photomicrograph of living organism. Bottom: 

 diagram of the same animal with labels of some of the structures that can be seen. 



This, of course, is not a haphazard occurrence. The amoeba can con- 

 trol these changes in protoplasm consistency and thus control the for- 

 mation and direction of the pseudopodia. 



Locomotion through the use of pseudopodia is called amoeboid move- 

 ment, but it is used by some other types of cells as well. In fact, some 



