32 DIGESTIVE ORGANS. 



the oesophagus, ju«t. behind the lingual wall (pi. 4, fig. 2*7), is 

 dilated below into a longitudinal pouch Avhich 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 roiuid nuclei. A similar organ has been 

 detected in 8pe<'ies of Murex. Yoluta (pi. 4, flg. .3.3), Ancill- 

 ."tria, etc. 



The 'Stomach, in its sinijjlest form (pi. 4. fig. 38), is a dilata- 

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

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

 origins of the (esophagus and intestine approximate. In many 

 of the species a blind saclv 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 liyaline 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 o?sophagus, or. in consequence of the bend- 

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

 (esophagus ; it then bends forM'ards, terminating in an anus 

 situated not far fro)n 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 I'ectum, 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 b}- the anus. 



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

 cles ; situated in the anterior part of the respiratory cavit3% 

 lying on the right side of the animal. 



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

 agus (behind the oesophageal 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 



