PROTOMONADINA 287 



D. socialis K. (Fig. 129, g). Oval flagellum about 2-3 times the 

 body length; lorica yellowish or pale brown; broadly spindle in form; 

 about ISjLt long; pond water. 



Genus Streptomonas Klebs. Free-swimming; naked; distinctly 

 keeled ; fresh water, 



S. cordata (Perty) (Fig. 129, h). Heart-shaped; 15/x by 13/x; rota- 

 tion movement. 



Genus Dinomonas Kent. Ovate or pyriform, plastic, free-swim- 

 ming; 2 flagella, equal or sub-equal, inserted at anterior extremity, 

 where large oral aperture, visible only at time of food ingestion, is also 

 located, feeding on other flagellates; in infusions. 



D. vorax K. (Fig. 129, i). Ovoid, anterior end pointed; 15-16^. 

 long; flagella longer than body; hay infusion and stagnant water. 



Family 8 Monadidae Stein 



Two unequal flagella; one primary and the other secondary; swim- 

 ming or attached; 1-2 contractile vacuoles; colony formation fre- 

 quent; free-living. 



Genus Monas Mliller (Physomonas Kent). Plastic and actively 

 motile ("dancing movement"); often attached to foreign objects; 

 not longer than 20ju; known for a long time, but still very incom- 

 pletely. Krijgsman (1925) studied the flagellar movements (p. 111). 



M. guttula Ehrenberg (Fig. 130, a). Spherical to ovoid; 14-16/x 

 long; free-swimming or attached; longer flagellum about 1-2 times 

 body length; cysts 12ju in diameter; stagnant water. 



M. elongata (Stokes) (Fig. 130, b). Elongate; about ll/x long; free- 

 swimming or attached; anterior end obliquely truncate; fresh water. 



M. socialis (Kent) (Figs. 8, g; 130, c). Spherical; 5-10/i long; 

 among decaying vegetation in fresh water. 



M. vestita (Stokes) (Fig. 130, d). Spherical; about 13. 5m in diam- 

 eter; stalk about 40/x long; pond water. Reynolds (1934) made a 

 careful study of the organism. 



M. sociabilis Meyer. Body 8-10^ long by 5^; two unequal flagella; 

 the longer one is as long as the body and the shorter one about one- 

 fourth; 20-50 individuals form a spheroid colony, resembling a 

 detached colony of Anthophysis; polysaprobic. 



Genus Stokesiella Lemmermann. Body attached by a fine cyto- 

 plasmic thread to a delicate and stalked vase-like lorica; 2 contrac- 

 tile vacuoles; fresh water. 



S. dissimilis (Stokes) (Fig. 130. e). Solitary; lorica about 28/i long. 



S. leptostoma (S.) (Fig. 130, /). Lorica about IT/n long; often in 

 groups ; on vegetation. 



