350 PROTOZOOLOGY 



oles; feeds on various Protozoa and also small invertebrates; may- 

 take 20 Paramecium within one food-cup; plasmotomy into 2-6 

 smaller individuals. North America (North Carolina (Wilson); Vir- 

 ginia (Kepner and Edwards) ; Tennessee and New Jersey (Schaeff er) ; 

 Illinois (Kudo)) and Great Britain (McGuire). 



Genus Vahlkampfia Chatton and Lalung-Bonnaire. Small amoe- 

 bae; vesicular nucleus with a large endosome and peripheral chro- 

 matin; with polar caps during nuclear division; snail-like movement, 

 with one broad pseudo podium; cysts with a perforated wall; fresh 

 water or parasitic. 



V. Umax (Dujardin) (Fig. 163, c). 30-40^1 long; fresh water. 



V. patuxent Hogue (Fig. 163, d). In the alimentary canal of the 

 oyster; about 20^ 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; ho lo zoic on 

 bacteria; multiplication by fission or budding; encystment rare; 

 cysts uninucleate. 



Genus Hartmannella Alexeieff. Small amoebae, with moderately 

 or well-developed ectoplasm; vesicular nucleus with a large endo- 

 some; mitotic figure ellipsoidal or cylindrical, without polar caps. 

 Cysts rounded; wall smooth or slightly wrinkled in one species. 

 Several species. Volkonsky (1933) distinguishes four groups. 



H. hyalina (Dangeard). 20-25)u in diameter; ectoplasm well 

 developed; endoplasm vacuolated; slender pseudo podia extend in 

 different directions; Hartmann and Chagas observed a centriole in 

 the endosome. 



Genus Acanthamoeba Volkonsky. Small amoebae similar to Hart- 

 mannella; ectoplasm is not well developed; mitotic figure at the end 

 of metaphase, a straight or concave spindle with sharply pointed 

 poles. Cysts enveloped by two membranes, the outer envelope being 

 highly wrinkled and mammillated. Several species. 



A. castellanii (Douglas) (Fig. 163, g, h). In association with fungi 

 and certain bacteria; Hewitt obtained the organism from agar cul- 

 tures of sample soil taken from among the roots of white clover; co- 

 existing with yeast-like fungi, Flavohacterium trifolium and Rhizo- 

 bium sp.; 12-30/1 in diameter; some cysts are said to remain viable 

 at 37°C. for 6 days. 



A. hyalina (Dobell and O'Connor) (Fig. 163, e, /). According to 

 Volkonsky, the organism described by Dobell and O'Connor as 

 Hartmannella hyalina, is transferred to this genus. Small amoeba; 

 9-1 7)u in diameter when rounded; a single contractile vacuole; binary 



