CILIATE PROTOZOA (INFUSORIA) 



295 



IQI (192) Bodies bell-shaped, usually transversely striated; peristomal disk 

 broad. Stalk containing a canal but no muscle. 



Epistylis Ehrenberg. 

 Representative species. . . . Epistylis flavicans Ehrenberg 1830. 



The species may be distinguished by the fact that the 

 stem is hollow throughout except the joints which are 

 solid. Another peculiarity is the curvature which each 

 limb makes as it leaves the point of bifurcation in the 

 dichotomously branching system. 



Five or six circles of strong cilia about the disk. Bodies 

 usually pale yellow in color. Nucleus band-like, curved. 

 When old the stalk loses its rigidity and the colony falls 

 down in a tangled mass. The same decumbent condi- 

 tion of a normal, upright colony may be produced by 

 removing its customary food supply. Conjugation of 

 free-swimming microgametes with attached macroga- 

 metes is common. Length of zooids 200 to 350 /* At- 

 tached to leaves, sticks, stones, etc., in running streams 

 or fresh-water pools. 



FIG. S44- Epistylis flavicans. macg, macrogamete; micg, 

 microgamete. X 25. (After Kent.) 



192 (191) Bodies elongate-ovate; peristomal disk not broad, elevated a con- 

 siderable distance . Opercularia Stein. 



Representative species. . . . Opercularia plicatilis Stokes 1884. 



Bodies elongate-ovate, smooth, soft and flexible, about three times 

 as long as broad. When contracted, zooids are thrown into transverse 

 folds posteriorly and bear longitudinally plicate, snout-like projections 

 in front. Protoplasm enclosing green corpuscles. Ciliary circles two. 

 Stalk rigid, striate longitudinally. Zooids in sessile groups of from ten 

 to twenty. Length of body 250/1- Height of colony 2.5 mm. At- 

 tached to plants in pond water. 



FIG. 545. Opercularia pltcatilts. X 25. (Alter Stokes.) 



193 (170) With a lorica 194 



194 (197) Lorica gelatinous. 195 



