HOLOTRICHA 553 



end; with 3-4 caudal cilia; macronucleus spherical, central; con- 

 tractile vacuole terminal; in fresh or salt water. 



C. niargaritaceum P. (Fig. 251, k). 15-45^ long; in fresh and 

 brackish water. 



Genus Dexiotrichides Kahl (Dexiotricha Stokes). Reniform; 

 compressed ; cytostome near middle, with 2 membranes ; long cilia 

 sparse; a special oblique row of cilia; a single caudal seta; contrac- 

 tile vacuole terminal; spheroidal macronucleus anterior; a micro- 

 nucleus; in fresh water. One species. 



D. centralis (Stokes) (Fig. 252, a). About 30-45m long; in de- 

 caying vegetable matter. 



Genus Cyrtolophosis Stokes. Ovoid or ellipsoid; with a muci- 

 laginous envelope in which it lives, but from which it emerges at 

 will; cytostome near anterior end with pocket-forming mem- 

 brane; on right side a short row of special stiff cilia, bent ven- 

 trally; sparse ciliation spiral to posterior-left; spherical macronu- 

 cleus central; a contractile vacuole; in fresh water, 



C. mucicola S. (Fig. 252, h). 25-28/x long; in infusion of leaves. 



Genus Urocentrum Nitzsch. Short cocoon-shaped, constricted 

 behind the middle; ventral surface flat; 2 broad girdles of cilia; 

 fused cilia at posterior end; with a zone of short ciha in the con- 

 stricted area; cytopharynx directed toward left, with a stiff ecto- 

 plasmic membrane which separates 2 undulating membranes (on 

 left) and cihated zone (on right) ; macronucleus, horseshoe-shape, 

 posterior; a micronucleus; contractile vacuole terminal, with 8 

 long canals which reach the middle of body; in fresh water. 



U. turho (Muller) (Fig. 252, c). 50-80^ long; Kidder and Diller 

 (1934) studied its fission. 



Genus Urozona Schewiakoff. Ovoid, both ends broadly round- 

 ed; a distinct constriction in middle where occur cilia; this ciliary 

 band composed of 5-6 rows of cilia, directed anteriorly and ar- 

 ranged longitudinally; cytostome with a membrane; rounded 

 macronucleus and a micronucleus posterior; contractile vacuole 

 subterminal; in fresh water. 



U. hutschlii S. (Fig. 252, d). 20-25ju long (Kahl) ; 30-40^ (Schew- 

 iakoff) ; in stagnant water. 



Genus Uronema Dujardin (Cryptochilum Maupas). Oval to 

 elongate ovoid; slightly flattened; anterior region not ciliated; 

 inconspicuous peristome with ciliated right edge; cytostome on 

 the ventral side close to left border in the anterior half, with a 



