IV. CILIATA: HYPOTRICIIA, SUCTORIA 



197 



folding in the anterior end. Vorticrlla* is solitary; Carchesium* forms colonies 

 with branched stalks; Zoothamnion,* colonies imbedded in a common jelly; 

 Epistylis* (fig. 52), branched colonies with rigid stalks. 



The fantastic Ophryoscolex, Cycloposthinm, etc., are parasites in the stomach 

 of ruminants. 



Order IV. Hypotricha. 



In this order the body is more or less flattened and ventral and dorsal sur- 

 faces are differentiated. The back lacks cilia, but often bears spines and bristles. 

 On the ventral side are several longitudinal rows of cilia, and also straight spines 

 and hooked cirri composed of united cilia, of use in creeping. The cilia are 



$ 



w ~~ 



rif-/- , 



FIG. 156. FIG. 157. 



FIG. 156. Stylonychia wytilns (after Stein), a, anal hooks; b, ventral hooks; c, 

 contractile vacuole; d, frontal ridge; g, canal leading to contractile vacuole; /, upper 

 lip; n, nucleus with micronucleus; f>, adoral ciliated spiral; r, marginal cilia; s, caudal 

 cilia; 5^, frontal spines; z, anus (cytopyge). 



FIG. 157. Division of Stylonychia invlilus (after Stein), c, c', contractile vacuoles 

 of the two individuals; n, nucleus and micronucleus; />, />', adoral ciliated spiral; r, r', 

 marginal cilia; w, w', ciliated ridges. 



used in locomotion and producing vortices which bring food. The macro- 

 nucleus is often divided into two oval bodies connected by a thread; the micro- 

 nuclei vary in number from 2 to 4 in the same species. These are the best forms 

 for studying the micronuclei. Stylonychia* (figs. 156, 157). 



Order V. Suctoria (Acinetaria). 



The Suctoria differ from other Infusoria in the absence of cilia from the 

 adult and consequently have no means of locomotion. They are fixed to some 

 support either by the base or by a slender stalk. The body is usually spherical 



