II 



PHYLUM PROTOZOA 



temporary anal spot described 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 

 loric-a, formed of a chitinoid material, and reminding us of the 



FIG. (U. Vorticella. A, B, living specimens in different positions , C, optical section ; Di, D^, 

 diagrams illustrating coiling of stalk; E 1 , E-, two stages in binary fission; E3, free zooid ; 

 Fl, F-, division into mega- and microzooids ; G 1 , G-, conjugation; H 1 , multiple fission of 

 encysted form ; H-, H3, development of spores ; ax. f. axial fibre ; cort. cortex ; cu. cuticle ; 

 c. rac. contractile vacuole ; <l. disc; <jvll. gullet'; m. microzooid ; mth. mouth; nu. mega- 

 nucleus; per. peristnme. (From Parker' 



similar structure found in so many of the Mastigophora. Some 

 (Fig. 62, 4} have bell-like shells, variously ornamented, and in 

 others (Fig. 63, 1) the similarly shaped shell is perforated and 

 resembles the skeleton of some of the Radiolaria. 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 opercu um (3) is 



