CILIATE PROTOZOA (INFUSORIA) 



293 



182 (183) Stalk retractile. Body bell-shaped, cuticle often ringed. A series 

 of strong cilia encircle the central, elevated ciliary disk. 

 Mouth eccentric between the peristome and ciliary disk. 



Nucleus band-like, curved Vorticella Ehrenberg. 



Representative species. . . Vorticella campanula Ehrenberg 1838. 



Body broadly campanulate, greatly dilated anteriorly, surface smooth. 

 Stalk thick, five or six times the length of the body. Endoplasm often 

 opaque with granules. Length of body 150 p. Pond water. Social. 



FIG. 539. Vorticella campanula. X 50. (After Kent.) 



183 (182) Stalk not retractile 184 



184 (185) With an operculum. Body ellipsoidal to ovate; the ciliary disk 

 upon a stalk, closing like a lid. Nucleus short or band-like. 



Pyxidium Kent. 

 Representative species Pyxidium ramosum Stokes 1887. 



Body vasiform, widest centrally; surface smooth. Ciliary disk slightly 

 exserted with two circles of long fine cilia. Pedicel very short. Length of 

 body about 100 M- Pond water on rootlets of Lemna. 



FIG. 540. Pyxidium ramosum. X 335. (After Conn.) 



185 (184) Without an operculum. Body elongate-ovate with surface usu- 

 ally transversely striate, stalk short. . . Rhabdostyla Kent. 

 Representative species Rhabdostyla vernalis Stokes 1887. 



Body widest centrally, constricted below the peristome border. Ciliary 

 circles two. Nucleus band-like. Length 50 /*. Attached to Cyclops and 

 Cypris in early spring. 



FIG. 541. Rhabdostyla vernalis. cv, contractile vacuole. X 660. (After Stokes.) 



186(181) Stalk branched . 187 



