PROTOZOA 



13 



undulating membrane, which, must be distinguished from the structures 

 of the same name which are formed by the fusion of ciUa. When there 

 are two flagella, it often happens that one is trailed behind the body 

 and the other directed forwards (Figs. 47 D, 53 C, 70 B). Flagella are 

 often used for anchoring, and sometimes appear to have a sensory 



^^ 



Fig. 13- 



- - vih. 



ba.lam. 



■tl.fi. 



ba.fi. 



Fig. 14. 



\ 



Fig. 15. 



Fig. 13. Diagram illustrating the optical appearance given by a profile view 



of cilia beating in metachronal rhythm. After Verworn. 



Fig. 14. Three membranellae from the adoral wreath of Stentor. After 



Doflein. vib. vibratile elements; the band beneath each of these represents 



the fused basal granules of the constituent cilia; ba.lam. basal lamellae; tl.fi. 



terminal fibres; ba.fi. basal fibre of the rhizoplast system. 



Fig. 15. Paramecium, showing the motorium lying near the vestibule, and the 



fibrils which radiate outwards. After Rees. 



function. Cilia are smaller and more numerous lashes which by a row- 

 ing action repeated by one after another of them In "metachronal 

 rhythm " (Fig. 13) cause movements of the animal or of the water near 

 It. Like flagella they have each an internal filament, a basal granule, 

 and a rhizoplast, which, however, does not connect with the nucleus. 



