244 



FRESH-WATER BIOLOGY 



10 (n) Pseudopodia ray-like with swellings along their course. Flagella 



directed forward Acinetactis Stokes. 



Representative species. . . . . . Acinetactis mirabilis Stokes 1886. 



Body subspherical, soft, and plastic. Short, lobate pseudopodia 

 often in addition to capitate rays. Flagella subequal arising at 

 some distance from each other. Nucleus central; contractile vacu- 

 oles two. Diameter about 12 . Stagnant pond water. 



FIG. 364. Acinetactis mirabilis. X 700. (After Stokes.) 



ii (10) Pseudopodia lobe-like. Flagella two, one trailing. Cercobodo Kraas. 

 Representative species Cercobodo sp. 



Species not determined. 



FIG. 365. Cercobodo sp. X 1250. (After Conn.) 



12 (5) Plastic but not forming pseudopodia. Flagellum single. 



Family CERCOMONADIDAE 



13 (14) With a posterior tail-like filament Cercomonas Dujardin. 



Representative species. . . Cercomonas longicaudata Dujardin 1841. 



Body elongate-ovate, fusiform, terminating 

 posteriorly in a long, tail-like filament about 

 twice the length of the body. Nucleus spher- 

 ical, subcentral. Length 10 \n. Vegetable 

 infusions. 



FIG. 366. Cercomonas longicaudata. cv, contractile 

 vacuole; n, nucleus X 1200. (After Stein.) 



14 (13) Without a tail-like filament Oikomonas Kent. 



Representative species Oikomonas steinii Kent 1880. 



Body, in motile condition, exceedingly plastic with a single 

 flagellum at the anterior end and a lip-like extension which as- 

 sists in taking food; in sedentary state, pyriform and attached 

 by posterior extremity. Nucleus posteriorly located. Length, 

 when contracted, about 20 to 30 ju. Vegetable infusions. Social. 



FIG. 367. Oikomonas steinii. cv, contractile vacuole; , nucleus. 

 X 440. (After Blochmann.) 



