T 



Chapter 40 

 Order 2 Spirotricha Blitschli (continued) 



Suborder 4 Hypotricha Stein 



HE members of this suborder are, as a rule, flattened and 

 strong cilia or cirri are restricted to the ventral surface. 

 Except the family 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, 6). Asexual reproduction is by binary fission and 

 sexual reproduction by conjugation (p. 148). Encystment is 

 common. Mostly free-living in fresh, brackish or salt water; a 

 few parasitic. 



Adoral zone fullj^ formed; dorsal surface with bristles 



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



Family 1 Oxytrichidae 



Ventrals and marginals not in long'itudinal rows 



Family 2 Euplotidae (p. 611) 



Adoral zone reduced; without dorsal bristles 



Family 3 Aspidiscidae (p. 613) 



Family 1 Oxytrichidae Kent 



Genus Oxytricha Ehrenberg ( Histrio Sterki ; Opisthotricha 

 Kent; Steinia Diesing). Ellipsoid; flexible; ventral surface flat- 

 tened, dorsal surface convex; 8 frontals; 5 ventrals; 5 anals; short 

 caudals ; marginals may or may not be continuous along posterior 

 border; macronucleus in 2 parts, rarely single or in 4 parts; fresh 

 or salt water. Numerous species. 



0. fallax Stein (Fig. 273, a). Posterior region broadly rounded; 

 about 150m long; fresh water. 



0. hifaria Stokes (Fig. 273, h). Right side convex; left side 

 flattened; posterior end pointed; about 250^ long; fresh water 

 infusion. 



0. Iudibu7ida S. (Fig. 273, c). Elhpsoid; flexible; 100m long; 

 fresh water among sphagnum. 



603 



