FLAGELLATE PROTOZOA (MASTIGOPHORA) 257 



in (no) Two flagella, unequal .- . . 112 



112(113) Body with spiral ridges Tropidoscyphus Stein. 



113(112) Body without spiral ridges 114 



114 (115) Trailing flagellum very prominent, curving around the anterior 



end Anisonema Dujardin. 



Representative species. . . . Anisonema acinus Dujardin 1841. 



Body wider posteriorly, flattened ventrally; anterior vi- 

 bratile flagellum short. Mouth near the base of the an- 

 terior flagellum. Length 25 /* Among diatoms. Common. 



FIG. 414. Anisonema acinus. X 500. The genus Metanema Klebs resembles Anisonema but is 

 (After Conn.) flexible. 



115(114) Trailing flagellum not prominent 116 



116 (1.17) Primary flagellum carried obliquely forward, vibratile only at its 

 end. Body ovate or angular with dorsal side concave. 



No protrusile pharynx Notosolenus Stokes. 



Representative species . . Notosolenus orbicularis Stokes 1884. 



Body with a broad, shallow, dorsal concavity; the ventral surface convex. 

 Movements somewhat eccentric, the convex surface usually directed down- 

 ward. Nucleus to the left of the center of the body. Contractile vacuole 

 near the anterior end. Length 10 to 12 ft. Bottom of shallow ponds. 



FIG. 415. Notosolenus orbicularis. X 1000. (After Conn.) 



117 (116) Primary flagellum not carried obliquely forward; pharynx pro- 

 trusile. A strong furrow on the ventral surface. 



Entosiphon Stein. 

 Representative species. . . Entosiphon sulcatus Stein 1878. 



Body oval, flattened; anterior border oblique, with a concavity at the 

 bottom of which is the mouth leading into a long tubular pharynx. 

 Nucleus posterior. Contractile vacuole anterior. Length 22 M. Pond 

 water, among aquatic plants. 



FIG. 416. Entosiphon sulcatus. X 500. (After Conn. 



118(2) With protoplasmic collars. . . Subclass Choanoflagellata . . 119 

 119(122) Not forming colonies 120 



