PROTOZOA 



II 



Form and Structure. — The 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 ecto- 

 plasm; and a granular, in- 

 ternal part, the endoplasm. 

 Is there a distinct line be- 

 tween them? (Fig. 10.) 



Fig. 10.- 



P3. 



Amceba. 



cv, contractile vacuole; ec, ectoplasm; en, 

 endoplasm; «, nucleus; ps, pseudopod; 

 ps , pseudopod forming; ectoplasm pro- 

 trudes and endoplasm flows into it. 



Note the central portion 

 and the slender prolonga- 

 tions or pscudopods (Greek, 

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

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

 regularity ? 



Sometimes it is possible to see a denser appearing por- 

 tion, called the nice lens ; also a clear space, the contractile 

 vacuole (Fig. io). 



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. 1 1). There is a new foot 

 made for each step. 

 Feeding. — If the amceba 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 amoeba seen 

 at different times. 



