20 



MORPHOLOGY OF PROTOZOA 



attached to objects by means of filaments, and in such cases a cone- 

 shape is developed, the filament of attachment arising from the apex of 

 the cone (Fig. 19). Amongst truly parasitic Protozoa the body may be 

 a motionless'sphere, as in the growing phases of coccidia within the cyto- 

 plasm of cells; on the other hand, those which live in fluids in the body 

 spaces and are endowed with powers of 

 active movement, like free-living forms, 

 vary considerably in shape. 



Amongst the Rhizopoda the body is 

 usually either globular or irregular in 



-Cfi 



Fig. 5. — Amceba proteus ( x 200). 

 (After Leidy, 1879.) 



Fig. 6. 

 1,000). 



—Eiiglena viridis ( x ca. 

 (After Doflein, 1916.] 



C, Contractile vacuole ; Ch, chromato- 

 phores; R, reservoir; S, stigma. 



shape, and there is no differentiation between an anterior and posterior 

 end or a dorsal or ventral surface (Fig. 5). In certain forms, however, 

 the body is protected by a shell, through an aperture in which pseudopodia 

 are extruded for purposes of locomotion and capture of food. In such 

 forms, of which Arcella and Difflugia are examples, it is possible to con- 



