246 FRESH-WATER BIOLOGY 



21 (16) Without lorica; one or more flagella. 



Family HETEROMASTIGIDAE . . 22 



22 (29) Not forming colonies 23 



23 (26) Flagellum single 24 



24 (25) Flagellum directed forward Leptomonas Kent. 



Representative species Leptomonas sp. 



Body pointed anteriorly and very flexible. Flagellum long and active. 

 Often parasitic. Fig. 371 represents a form reported by Conn, taken from a 

 watering trough, and assigned to this genus with some doubt. 



Species not determined. 



FIG. 371. Leptomonas sp. X 875. (After Conn.) 



25 (24) Flagellum trailing Rhynchomonas Klebs. 



Representative species Rhynchomonas nasula Klebs 1886. 



Body ovate, slightly compressed, anterior end prolonged 

 into a movable process. Mouth near the anterior end. 

 Nucleus central. Contractile vacuole anterior. Fresh 

 water. 



FIG. 372. Rhynchomonas nasula. X 1500. (After Conn.) 



26 (23) Two or more flagella 27 



27 (28) Body free or attached by an attenuated posterior end; spherical to 



ovate, with one chief flagellum and one or two secondary 



ones. Moderately flexible Monas Ehrenberg. 



Representative species Monas fluida Dujardin 1841. 



FIG. 373. Monas fluida. CD, contractile vacuole; n, nucleus; 5, stigma; m, mouth. 



X 1000. 



