MOLLUSCA. 467 



a. Anus situate near the posterior extremity of the back, 

 and surrounded with a fringe of pkimose branehife. 



31. Doris. Oral tentacula two ; vent without scales. 



The cloak is covered with retractile papilla?, and sepa- 

 rated from the foot by a distinct duplicature. Towards 

 its anterior margin are placed the two superior tentacula. 

 These are retractile, surrounded at the base with a short 

 sheath, and supported on a slender stem, having an en- 

 larged compound plicated summit. The neck is short, and 

 above the mouth there is a small projecting membrane, 

 connected at each side with the oral tentacula, which are 

 in general minute, and of difficult detection. 



The mouth is in the form of a short trunk, leading to 

 fleshy lips, within Avhich the tongueis placed. This last organ 

 is covered with minute reflected hairs, and, from its motion, 

 appears to be destined exclusivelyfor deglutition. Thegullet 

 is a simple membranaceous tube, terminating in a stomach, 

 which presents on the interior a few longitudinal folds. It is 

 furnished with a small csecum, the extremity of which re- 

 ceives the bile from the liver. The stomach likewise re- 

 ceives the secretion of another gland, which is not connected 

 with the liver, in the form of a small bag, the inner surface 

 of which is covered with numerous papillae. The intestine 

 is lodged in a groove on the surface of the liver, and pro- 

 ceeds directly to the anus. 



The liver itself is divided into two lobes, and gives rise 

 to numerous bihary ducts, which proceed to the stomach. 

 But it likewise gives rise to a duct which proceeds to a 

 small bag plaited on the inside, and afterwards opens on 

 the surface at a small hole near the anus. It yet remains 

 to be determined, whether the fluid carried off" by this con- 

 duit be excrementitious matter, separated by the liver, or 

 whether the gland which produces it be distinct from that 



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