II 



PHYLUM PROTOZOA 



87 



temporary anal spot describe. I in Paramcecium, a distinct anal 

 aperture (.). 



Most of the Ciliata are naked, having no shell or other form of 

 skeleton ; but in a few forms the body is provided with a shell or 

 lorica, formed of a chitinoid material, and reminding us ,,f the 



per. 



H* 



FIG. 04. Vorticella. A, B, living specimens in different positions ; 0, optical section; D 1 , I)-, 

 diagrams illustrating coiling of stalk; E 1 , E-, two stages in binary fission; E :i , five /nol>l ; 

 FI, F-, division into mega- and microzooids ; Gi, G-, conjugation; in, multiple fission i 

 encysted form; H-, H 3 , development of spores; ax. f. axial fibre; t-oi-t. cortex; re. cuticle; 

 c. rac. contractile vacuole ; d. disc; (lull, gullet; t. microzonid ; mtk. mouth; nu. mega- 

 nucleus ; pi:/', peristumo. (From Parker's Binli><in.) 



similar structure found in so many of the Mastigophora. Some 

 (Fig. 62, 4} have bell-like shells, variously ornamented, ;tn<l in 

 others (Fig. 63, _?) the similarly shaped shell is peril traifd ;md 

 resembles the skeleton of some of the Radiolnria. A chitinoid 

 plate or operculum (Fig. 63, 2, op.} may be fixed to the edge of the 

 peristome, and, when the animal is retracted in its case accurately 

 closes the mouth of the latter, or a similar opereu urn (->') is 



