448 J. H. ORTON. 



the ventral face to the tip of the gill. (See the small transverse 

 arrow in Fig. 2.) Upon reaching the tips of the filaments the food 

 is deposited in a ciliated groove, which runs along the right side of 

 the body (see Fig. 2, B). This ciliated food-groove is just roofed in 

 by the tips of the filaments. These are flattened at this point the 

 more effectively to close in the groove (see Fig. 3), and just meet 

 the slightly upturned edge of the right epipodium. 



The food collected in this way becomes embedded in mucus and 

 formed into a cylindrical mass (see Fig. 1, B), which is at intervals 

 passed forward towards the mouth to be eaten. As the food-mass 

 approaches the mouth the animal shoots out the radula at it with 

 the marginal teeth spread apart, but on striking the food-mass these 

 teeth close in, and in this way obtain a hold on it. The radula is 

 now retracted and the food is thus drawn into the pharynx where 

 the mandibles assist in retaining it. The radula is then freed and 

 again shot out at another part of the food-mass, grasping and drawing 

 back another length. These operations are repeated until a length 

 of the food-material is broken off from the main mass. The detached 

 piece is then swallowed. 



This is not the only way, however, in which food reaches the mouth. 

 The majority of the larger particles of food-material, which are drawn 

 in with the food-current, have a different fate. On entering the in- 

 halent chamber they can be seen to be drawn forwards in a direction 

 almost at right angles to the main current (see the small arrow in Figs. 1 

 and 2), and become gathered together in the food-pouch which is placed 

 just in front of the mouth (see Figs. 1, A, 2,A, 4, A). In this pouch, which 

 is really a deep groove in a semicircular fold of skin, the food is worked 

 up with mucus into a pellet which may be eaten, but if considered 

 undesirable as food, it is carried by cilia to the edge of the shell or 

 pushed by the animal into the exhalent current. And, indeed, when a 

 large quantity of food-material is suddenly drawn into the mantle 

 cavity, the animal usually rejects the greater part of it by backing 

 into the cavity, covering the gills posteriorly so as to cut off most of 

 the current, and at the same time secreting a copious supply of mucus, 

 in which the intruding material becomes caught, and carried in the 

 current forwards. But instead of passing into the food-pouch, it is 

 carried further forward into a ciliated path which is situated immedi- 

 ately in front of and parallel with the food-pouch and deposited at the 

 extreme front of the shell (see Fig. 4, A). It has been noticed that the 

 food-material gathered in the food-pouch is often rejected, while that 

 in the food-groove is almost always eaten. Thus the food-pouch and 

 forwardly directed current are a means for separating and transferring 



