MOLLUSCA. 411 



analogous to that of mastication, in the higlier orders of ani- 

 mals. When the food is in the mouth, or entering into the 

 gullet, it is mixed Avith saliva, as in the more perfect ani- 

 mals. The salivary glands in which it is secreted, are in 

 general of considerable size, divided into lobes, and, in 

 some cases, separated into distinct masses. In many spe- 

 cies the existence of a gullet is doubtful, as the food seems 

 to enter the stomach immediately ; while, in others, there 

 is a portion of the intestinal canal which has some claim to 

 the denomination. 



The stomach, in many instances, is membranaceous, and 

 can scarcely be distinguished from the remaining portion of 

 the intestinal canal. In some cases, however, it is strong and 

 muscular like the gizzard of a bird, and even fortified with 

 corneous knobs for the reduction of hard substances. In 

 some species, the stomach opens laterally into the pylorus, 

 and, in a few instances, possesses a spiral ccecum attached 

 to it. 



The liver is usually of large dimensions, and seated close 

 to the stomach,' which it, in many cases, envelopes. It is 

 divided into numerous lobes, and receives numerous blood- 

 vessels. There is, however, nothing analogous to the vena 

 portarum of quadrupeds. The hik is poured, in some, into 

 the stomach, and, in others, into the pyloric extremity of 

 the intestine by different openings. There is no gall- 

 bladder. 



There is no division of the canal into small and large in- 

 testines, as in the higher classes ; or rather, among the mol- 

 lusca, the relative size of the different parts is reversed. 

 Here the pyloric extremity is usually the largest, while the 

 anal is more slender. The intestine, as in fishes, is short in 

 proportion to the length of the body, and, in its course, is 

 subject to few turns. The anus is, in some, placed on one 



