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APPLIED BIOLOGY 



The body of an amoeba consists of protoplasm, imbedded 

 in which are many food particles that have been eaten and 

 not yet digested. The outermost protoplasm is perfectly 

 transparent and colorless, while the central portion is very 

 granular and resembles ground or frosted glass. The micro- 

 scope and drawings give the impression that the animal is a 

 thin sheet of protoplasm, spread out like a liquid poured on 



FIG. 91. Amoeba. Arrows show direction of flowing of the protoplasm 

 n, nucleus ; fv, food vacuole ; wv, water vacuole ; cv, contractile vacuole ; 

 p, temporary posterior end. (From Wilson.) 



a flat plate ; but when the animal is disturbed (as by jarring) 

 it rolls up into a rounded mass. 



Movement. The most noticeable thing about an active 

 amoeba is that it is continually changing its shape. Close 

 observation will show that this is due to the fact that the 

 animal is composed of semi-fluid protoplasm which is con- 

 stantly flowing. This movement of the protoplasm is not 

 like the flowing of water down an incline, but is due to con- 

 tractions originating within the amoeba itself. It is possible 

 for the animal to crawl up the stem of a water plant, and 

 this could not be explained by the laws of gravitation. 



