310 PROTOZOOLOGY 



floating; pseudopodia numerous, conical; ectoplasm clear, usually 

 with cils; endoplasm with food vacuoles, oil (?) spherules and 

 large clear globules; nucleus and contractile vacuole obscure; 

 spherical forms 64-160^1 in diameter; creeping forms 152-340/1 by 

 60-220/x; in sphagnous swamp. 



Genus Pelomyxa Greeff. Large sluggish amoebae; with a few 

 to numerous nuclei; cytoplasm poorly differentiated; pseudopodia 

 few, short, and broad; animal undergoes rolHng movement; with 

 diatoms, bacteria, water vacuoles, sand grains and refractile 

 bodies which are thought to be either reserve food material simi- 

 lar to glycogen or metabohc products used by symbiotic bac- 

 teria; contractile vacuole has not been noticed with certainty, 

 multiphcation by binary fission; gamete formation has been re- 

 ported; it is presumed that uninucleate bodies undergo fusion to 

 form zygotes which develop into multinucleate forms; fresh wa- 

 ter. Several species. 



P. palustris G. (Fig. 142, a). Large; 150^-2 mm. or larger in 

 diameter; sluggish with one broad pseudopodium by which the 

 organism undergoes rolling movement; cytoplasm undifferen- 

 tiated; numerous vacuoles and nuclei; various inclusions often 

 color the body brown to black and make it appear opaque; sym- 

 biotic protophytan, Cladothrix pelomyxae Veley, occurs regularly; 

 cysts with 2-3 envelopes ; cyst contents divide into several multi- 

 nucleate bodies; in stagnant water, creeping on the muddy bot- 

 tom. 



P. villosa (Leidy) (Fig. 142, h). Similar to the last-named spe- 

 cies, but somewhat smaller; with numerous short and papillary 

 villi at posterior extremity; during locomotion, about 250/^ long; 

 in the ooze of freshwater bodies. 



Genus Vahlkampfia Chatton et Lalung-Bonnaire. Small amoe- 

 bae; vesicular nucleus with a large endosome and peripheral 

 chromatin; with polar caps during nuclear division; snail-hke 

 movement, with one broad pseudopodium; cysts with a perfo- 

 rated wall ; fresh water or parasitic. 



V. Umax (Dujardin) (Fig. 142, c). 30-40// long; fresh water. 



V. patuxent Hogue (Fig. 142, d). In the alimentary canal of the 

 oyster; about 20/i long during the first few days of artificial culti- 

 vation, but later reaching as long as 140/i in diameter; ordinarily 

 one large broad fan-shaped pseudopodium composed of the ecto- 

 plasm; in culture, pseudopodium-formation eruptive; holozoic on 



