PROTOZOA 



I I 



Fig. io 



:>, contractile vacuole; ec, ectoplasm; en, 

 endoplasm; n, nucleus; /s, pseudopod; 

 ps' , pseudopod forming; ectoplasm pro- 

 trudes and endoplasm flows into it. 



Form and Structure. — The ameba (also spelled amoeba) 

 looks so much like a clear drop of jelly that a beginner 

 cannot be certain that he 

 has found one until it moves. 

 It is a speck of protoplasm 

 (Fig. 9), with a clear outer 

 layer, the ectoplasm ; and a 

 granular, internal part, the 

 endoplasm. Is there a dis- 

 tinct line between them ? 

 (Fig. 10.) 



Note the central portion 

 and the slender prolonga- 

 tions or pseudopods (Greek, 

 false feet). Does the endoplasm extend into the pseudo- 

 pods ? (Fig. 10.) Are the pseudopods arranged with any 

 regularity ? 



Sometimes it is possible to see a denser appearing por- 

 tion, called the nucleus ; also a clear space, the contractile 

 vacuole (Fig. 10). 



Movements. — Sometimes while the pseudopods are be- 

 ing extended and contracted, the central portion remains 



in the same place (this is mo- 

 tion). Usually only one pseudo- 

 pod is extended, and the body 

 flows into it; this is locomotion 

 (Fig. 11). There is a new foot 

 made for each step. 

 Feeding. — If the ameba crawls near a food particle, the 

 pseudopod is pressed against it, or a depression occurs (Fig. 

 12), and the particle is soon embedded in the endoplasm. 

 Often a clear space called a. food vacuole is noticed around 

 the food particle. This is the water that is taken in with 



Fig. 11. — The same ameba seen 

 at different times. 



