ON CILIARY MECHANISMS. 



291 



cilia on the ab-frontal face are similar to those on the frontal face (see 

 Fig. 6, below). Thus there are two broad zones of cilia on the filamentar 

 side of both faces of the lophophore lashing towards the filaments and so 

 assisting in producing the food-current, and two zones lashing towards 

 the inner edge of the lophophore, along which particles are carried 

 around the inside of the spiral to its base. At the bases of the two 

 arms of the lophophore the particles carried along the inner edge of the 

 lophophore are passed on to the lower mantle, whence they are expelled 

 from the mantle cavity. 



Fig. 6. — Semi-diagrammatic transverse section of the lophophore of Crania to show 

 the difference in the action of the ciUa on its various parts as indicated by the 

 adjoining arrows. 



A. Arrow indicating the direction in which the current-producing ciHa lash 



on the portion of the gill-filament E. 



B. Arrow indicating the direction in which the frontal cilia on the gill- 



filament lash. 

 B.gr. Buccal groove along which food is carried to the mouth. 

 B.I. Buccal lip. 



C. Inner edge of lophophore along which particles are carried to its base. 



D. Region from either side of which the cilia lash in opposite directions, 



resembling a watershed. 



E. Base of a gill-filament arising from the lophophore. 

 m. Mucus globules. 



It will now be seen that there are three factors concerned in the pro- 

 duction of the main food and respiratory stream in Crania — and probably 

 in most, if not all, Brachiopods — namely, the rows of lateral cilia on the 

 gill-filaments, which are the most important factor, the cilia on the 

 filamentar sides of the body of the lophophore, and the cilia on the mantle 

 lobes. 



Food-collection in Brachiopods is effected chiefly by the frontal cilia 

 on the gill-filaments, and partially by the cilia on the frontal face of the 

 outer side of the body of the lophophore. The cilia on the frontal face 



NEW .SERIES.— VOL. X. NO. 2. JUNE, 1914. T 



