244 



FRESH-WATER BIOLOGY 



10 (ii) 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 )i. Stagnant pond water. 



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



11(10) Pseudopodia lobe-Uke. Flagella two, one trailing. Cercobodo Kislhs. 

 Representative species Cercobodo sp. 



Species not determined. 



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



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



Family Cercomonadidae 



13 



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 ii. Vegetable 

 infusions. 



Fig. 366. Cercomonas longicaudata. ct, 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-Uke 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 jx. Vegetable mfusions. Social. 



Fig. 367. Oikomonas steinii. cv, contractile vacuole; », nucleus. 

 X 440. (After Blochmann.) 



