32 DIGESTIVE ORGANS. 



the oesophagus, just behind the lingual wall (pi. 4, fig. 27), is 

 dilated below into a longitudinal pouch which is filled up with 

 a gelatinous tough mass, projecting into the interior like a ridge : 

 it consists of a hyaline material, with many spindle-shaped or 

 stellate cells with round nuclei. A similar organ has been 

 detected in species of Murex. Yoluta (pi. 4, fig. 33), Ancill- 

 aria, etc. 



The stomach, in its simplest form (pi. 4, lig. 38), is a dilata- 

 tion of the digestive tract into which the hepatic ducts open. 

 In Murex and Buccinum it is rounded and curved so that the 

 origins of the oesophagus and intestine approximate. In many 

 of the species a blind sack has been detected in connection with 

 the stomach. In some there are internal lobes or filaments (as 

 in Mitra episcopalis), and in others actual tooth-like bodies for 

 compressing the food (Telescopium). In Bythinia, Strombus 

 and Pteroceras the blind sack has been found to contain a firm 

 body, somewhat like the hyaline rod of muscles ; it extends some 

 distance into the cavity of the stomach. 



The intestine in spiral shells may enter the stomach opposite 

 the entrance of the (esophagus, or. in consequence of the bend- 

 ing of the stomach, it most usually enters not far from the 

 (esophagus ; it then bends forwards, terminating in an anus 

 situated not far from the mouth. In the carnivorous species. 

 Murex, Triton, etc., the intestine is direct or nearly so, but in 

 the phytophaga it usually forms one or more convolutions (pi. 

 4, fig. 32 . The intestine may be distinguished into two por- 

 tions, the small intestine and the rectum, the latter being usually 

 enlarged in diameter, confined to the anal end and straight por- 

 tion of the tube, and having longitudinal folds of its inner wall. 

 In the female, the vagina is placed alongside the rectum, and in 

 some univalves there are anal glands opening by the anus. 



The anus is simply a round opening closing by sphincter mus- 

 cles ; situated in the anterior part of the respiratory cavity, 

 lying on the right side of the animal. 



Salivary glands. Usually a pair of these lie along the oesoph- 

 agus (behind the cesophageal ring), and open into it close to its 

 entrance into the oral mass. These glands may be tubular and 

 long, dilated behind as in Strombus, or the posterior extremity 

 cork-screwed as in Voluta (pi. 4, fig. 33), or they may be short 



