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J. H. ORTON. 



but towards the base of the gill on the inner faces. On the inner 

 lamellae the frontal cilia on both faces lash particles towards the free 

 edge of the gill into a well-defined food-groove. In Pecten, Kellogg 

 has described that in the troughs of the gills particles are lashed 

 towards the base of the gill, while on the crests particles are lashed 

 towards the edge. On the other hand, Stenta has shown that in 

 Anodon food-particles are washed towards the bases of the outer 

 lamellae but to the tips of inner lamellae. All these different modes 

 of food collection and transportation may be indicated in diagrammatic 

 form as in Fig. 14. This diagram will also indicate the mode of food- 

 collection and food-transportation in Nucula. I find that in Nucula 

 the gills divide the posterior region of the mantle cavity into infra- 

 and supra-branchial chambers as in the higher Lamellibranchs. The 



Fig. 14. — Diagram of the general mode of feeding in Lamellibranchs. 



The large thick-lined arrows indicate the paths of the main respiratory and 

 food -current. 



The dotted thin-lined arrows indicate the directions in which the mantle and 

 gill cilia wash the food-streams. The dotted thick-lined arrows leading from the 

 right gill-lamellae indicate the paths of the main food-streams towards the mouth. 



Food-collection is indicated on the left gill-lamellae, and food-transportation 

 on the right gill-lamellae. 



A. Point at which the heavier particles begin to settle out of the current. 



B. The ciliated path on the mantle which carries away material rejected by the palps, 

 and that collected from the mantle. 



C.P. The ciliated path seen in section on the mantle. 



C. The subsidiary mantle streams. 



L. & R. Left and right valves of shell, an<l the beginning of the left and right mantle 



lobes, 

 f.g. Main food-grooves. 

 f.c. Food-channels at bases of gills. 

 I.Ch. Inhalent chamber. 

 B.Ch. Exhaleut chamber. 

 G.L. Gill-lamellae. 

 M. Mouth. 

 To Ex. Ap. To exhalent aperture. 



