Chapter 41 

 Order 2 Spirotricha Blitschli (continued) 



Suborder 4 Hypotricha Stein 



THE members of this suborder are, as a rule, flattened and strong 

 cilia or cirri are restricted to the ventral surface. Except the fam- 

 ily Aspidiscidae, the dorsal surface possesses rows of short slightly 

 moveable tactile bristles. The peristome is very large with a well- 

 developed adoral zone. The cirri on the ventral surface are called, 

 according to their location, frontals, ventrals, marginals, anals 

 (transversals), and caudals, as was mentioned before (Fig. 11, b). 

 Asexual reporduction is by binary fission and sexual reproduction by 

 conjugation. Encystment is common. Mostly free-living in fresh, 

 brackish or salt water; a few parasitic. 



Adoral zone fully formed 

 Cirri on ventral surface 



Ventrals in rows, though in some reduced; 2 rows of marginals. . . . 



Family 1 Oxytrichidae 



Ventrals and marginals not in longitudinal rows 



Family 2 Euplotidae (p. 839) 



No ventral cirri; caudal cirri Family 3 Paraeuplotidae (p. 843) 



Adoral zone reduced Family 4 Aspidiscidae (p. 845) 



Family 1 Oxytrichidae Kent 



Genus Oxytricha Ehrenberg (Histrio Sterki; Opisthotricha Kent; 

 Steinia Diesing). Ellipsoid; flexible; ventral surface flattened, dorsal 

 surface convex; 8 frontals; 5 ventrals; 5 anals; short caudals; mar- 

 ginals may or may not be continuous along posterior border; macro- 

 nucleus in 2 parts, rarely single or in 4 parts; fresh or salt water. 

 Numerous species (Horvath, 1933); neuromotor system (Lund, 

 1935). 



0. fallax Stein (Fig. 354, a). Posterior region broadly rounded; 

 about 150^ long; fresh water. Amicronucleate race (Reynolds, 1932). 



0. bifaria Stokes (Fig. 354, b). Right side convex; left side flat- 

 tened; posterior end pointed; about 250m long; fresh water infusion. 



0. ludibunda S. (Fig. 354, c). Ellipsoid; flexible; 100m long; fresh 

 water among sphagnum. 



O. setigera S. (Fig. 354, d). Elongate ellipsoid; 5 frontals; ventrals 

 shifted anteriorly; 50m long; fresh water. 



Genus Tachysoma Stokes (Actinotricha Cohn). Flexible; frontals 

 8-10, of which anterior three are usually the largest; 5 ventrals 



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