454 J. H. ORTON. 



down or any other way, but if the animal be upside down a fairly 

 copious secretion of mucus becomes necessary to capture the particles. 

 In the normal position of the animal, however, that is, with the ventral 

 surface downwards and facing a little to the left, the disposition of the 

 parts is beautifully effective for separating the heavier food-particles, 

 as may be gathered from diagram (Fig. 7). From this diagram 

 it will be seen that the heavier particles are dropped into the ciliated 

 path on the left epipodium, and so may be passed forwards while the 

 lighter particles are carried onwards in the stream above. The cilia 

 on the left epipodium are only a part of the uniform covering of cilia 

 on the dorsal surface of the animal's " head " and " neck." The dis- 

 position of the cilia on the remaining parts, and the directions in which 

 these lash, may be gathered from a glance at Fig. 9. It will be noticed 

 that the cilia on the right side assist in washing particles into the 

 food-groove, while those on the dorsal surface of the " head " assist in 

 transferring food-particles to the food-pouch ; for it will be remem- 

 bered that the animal's head, as in Fig. 1, overlies the food-pouch. 



Fig. 9. — Dorsal view of a male Crepidula taken out of its shell and drawn from life, with 

 the mantle turned back. The arrows indicate the directions in which the various 

 groups of cilia lash, (Natural size.) 



ct. Gill filaments. 



IV. SUMMAEY OF ACCOUNT OF CUEKENT-PRODUCmO 

 MECHANISxM, AND MODE OF FEEDING IN CKEPIDULA. 

 The mode of feeding in Crepidula is thus seen to be as follows : — A 

 main food-current is produced through the mantle cavity by the lash- 

 ings of rows of cilia on the anterior, posterior, and dorsal surfaces of 

 the gill-filaments ; the current entering the mantle cavity on the left 

 at the front of the shell passing between the gill-filaments and out at 

 the front of the shell on the right. On entering the inhalent 

 chamber, however, the velocity of the stream falls owing to the 

 widening out of its path, so that while the heavier food-particles 



