CHAPTER XXVIII 



RHIZOPODA 



Amoeba Proteus.— This large saprophytic ameba may be 

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

 amebse, 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. 180. — A, Amoeba proteus engulfing a clump of small algae (iVa). Cv, con- 

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

 cy, cyst wall; n, nucleus; R, reserve food substance. C, Cyst containing many young 

 amebas beginning to escape; cy, cyst wall; k, young amebfe. (After Doflein.) 



5oo;tt 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 nucelus 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 



420 



