460 



J. H. ORTON. 



pelled along its somewhat precarious journey towards the palps by the 

 cilia in the open food-groove which is found along the distal edges of 

 the gill-lamellae of the oyster, and indeed of most other Lamellibranehs 

 (compare Figs. 14 and 15). 



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Fig, 12. — View of the mantle cavity of the common cockle, Cardium edule, to show the 



respiratory current and the currents connected with the mode of feeding. ( x f . ) 



C.P. Ciliated path on mantle which carries away the material rejected by the palps and 

 that collected from the mantle. 



A. Point at which heavier particles begin to drop out of main stream on to mantle, and 

 also the region on the mantle whence the material collected by the ciliated path is 

 finally shot out of the mantle cavity. 



B. Gill-shield directing the ingoing current ventral-wards. 



C. Point at which material is passed from the palps to the mantle. 

 fg. Food.groove at the ventral edge of the inner gill-lamella. 



P. Left outer palp, below the base of which lies the mouth. 



A. Ad. Anterior adductor. P. Ad. Posterior adductor. 



The dotted arrows on the mantle and foot indicate the directions in which the cilia 



lash. 

 The arrows on and at the edge of the gill indicate the paths of the food-streams. 



Such food-streams occur at the tips of the four lamellae, at the bases 

 of and between the lamellae, and also between the outer lamellae and 

 the mantle (see Fig. 14). The particles in the basal streams are 

 mostly washed to the tips of one or other of the gill-lamellae before 

 reaching the palps, but in any case the streams on each side of the 

 body eventually pour their burdens on to the palps, whence they are 

 conveyed either to the mouth or directed into the ciliated paths if 

 deemed undesirable as food (see Figs. 10 and 14). If the food is 

 accepted, the palps separate so as to allow it to pass between. The 

 cilia on the inner surfaces of the palps then quickly wash the food into 

 the mouth. If the food is rejected, the palps remain apposed, and 

 the cilia on their outer surfaces direct the food-mass on to the 

 ciliated path on the mantle whence it is conveyed outside the mantle 

 cavity. 



In Pecten and Mytilus the upturned edges of the outer gill- filaments 



