SOME PROBLEMS OF CILIARY STRUCTURE AND CILIARY FUNCTION 56 1 



^pi ip^ nrwrn -i^ 



Fig. 3. Section through a flagellated chamber of the marine sponge, Microciona 

 sp. Nine collar cells (choanocytes) have been cross-sectioned. In each of them the 

 flagellum (/) and the collar (r) can be seen. The collar is composed of about 30 

 separate microvilli. An enlargement of the marked area appears in Fig. 4. 

 Alagnification 20 000 x . 

 VOL. ir. — 20 



