CHAPTER XXVIII. 

 RHIZOPODA. 



Amoeba Proteus. This large saprophytic ameba may be 

 considered as an example of the numerous species of free-living 

 amebae, the classification and identification of which is still in 

 hopeless confusion. The organism is widely distributed in stag- 

 nant water and is easily cultivated in the laboratory in not too 

 foul infusions containing bacteria and algae. The cell is 50 to 



FIG. 172. A, Amoeba proteus engulfing a clump of small alg<2 (No). Cv, con- 

 tractile vacuole; N, nucleus. B, Newly encysted ameba showing nuclear fragments; 

 cy, cyst wall; w, nucleus; R, reserve food substance. C, Cyst containing man}'' young 

 amebaj beginning to escape; cy, cyst wall; k, young amebae. (After Doflein.) 



across, often possesses numerous thick, blunt pseudopodia. 

 The ectoplasm and endoplasm appear distinctly different, the 

 latter being filled with granules, crystals, vacuoles and food parti- 

 cles, such as algae and bacterial cells, and possessing a contractile 

 vacuole. The nucleus is lentil-shaped and the chromatin within 

 it has a very typical arrangement in a central plate surrounded 

 by a network on which the peripheral chromatin is symmetrically 

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