THE PROTOZOA 



15 



permanent in form, constantly beats backward and forward 

 with great rapidity in a general direction represented in 

 the diagram (Fig. 6, c). The movement from a to b is 

 much more rapid than the reverse, from b to , which 

 results, like the action of the human arm in swimming, in 

 driving the organism forward. Not only does the flagel- 

 lum serve the purpose of locomotion, but it also produces 

 currents in the water which 

 may serve to bear minute 

 organisms down into the 

 "gullet, whence they read- 

 ily pass into the soft pro- 



FIG. 6. Flagellate Infusoria. A, 

 Euglena viridis ; c, pulsating 

 vacuole ; e, eye-spot ; g, gullet ; 

 w, nucleus ; t, flagellum. B, Co- 

 dosiga, with collar surrounding 

 the flagellum. C, diagram illus- 

 trating the action of the flagel- 

 lum. All figures greatly enlarged. 



FIG. 7. Paramcecium aurelia, a 

 ciliate infusorian. c, cilia; c.v., 

 pulsating vacuoles ; /, food 

 particles ; g, gullet ; m, buccal 

 groove ; n, nucleus. 



toplasm of the body, there to undergo the processes of di- 

 gestion and assimilation. In some forms the protoplasm in 

 the region of the flagellum is drawn out in the form of a 

 collar (Fig. 6, B), whose vibratory motion also aids in con- 

 veying and guiding food into the body. 



18. The Slipper Animalcule. The second type of loco- 

 motor organ may be understood from a study of the 

 24 



