276 FRESH-WATER BIOLOGY 



47 (46) Body flattened ventrally, convex dorsally. With a long neck and 



usually a tail-like prolongation both of which are hyaline. 

 Mouth a slit at the base of the neck, often invisible. Nuclei 

 usually two; contractile vacuole posterior. 



Lio)iotus Wrzesniowski. 

 Representative species Lionotus urzcsniowskii Kent 1882. 



■^■^~^'"~~^-~^ Fk;. 479. Lionotus wrzesniowskii. cv, contractile 

 5- ^.jc^ - vacuole. X 125. (After Kent.) 



48 (35) ^louth usually somewhat posterior, and often with a pharynx; body 



oval or kidney-shaped 49 



49 (50) Body completely ciliated, cylindrical to ovate, rounded posteriorly. 



Mouth about one-third of the way from the anterior end; 



pharynx with rods Nassula Ehrenberg. 



Representative species Nassula oniata Ehrenberg 1838. 



Ifl^^l^ Usually some shade of red or brown in color. Nucleus 



_ ' W''"^^^ large, spherical, posteriorly located. Contractile vacuole 



0' -^ '0K-^ri^^ single. Length 200 m- Among algae 



Fig. 480. Nassula ornaia. In act of feeding. X 325. (After 

 Conn.) 



50 (49) Body not completely ciliated; cilia ventral only 51 



51 (56) Body flattened 52 



52 (55) Mouth in the anterior half of the body 53 



53 (54) Body with convex dorsal and flattened or slightly concave ventral 



surface. Pharynx with rods Chilodon Ehrenberg. 



Representative species Chilodon cucullulus Miiller 1 786. 



o The lip-like extension prominent, a groove leading from it to the 



mouth. Nucleus oval near the inner end of the pharynx. Contractile 

 vacuoles numerous. Length 125 to 200 m- Stagnant water and among 

 algae. 



Fig. 481. Chilodon cucullulus. cv, contractile vacuole; macn, macronucleus; 

 mic, micronucleus. X no. (After Blochmann.) 



54 (53) Body with ridges on dorsal and ventral surfaces, crenate in cross 



section, pharynx with rods Chilodonopsis Conn. 



Representative species Chilodonopsis crenida Conn 1905. 



Fig. 482. Chilodonopsis crenula. X 335. (After Conn.) 



55 (52) Mouth in the posterior half of the body Opisthodon Stein. 



56 (51) Body not flattened 57 



