MOLLUSCA. 15 



refuse to eat those which are dried. We are not aware that 

 putrid vegetable matter is consumed by them, although 

 many of the snails and slugs are found under putrid leaves 

 and decayed wood. In these places there is shelter from 

 the sun, together with dampness, so that it is difficult to de- 

 termine, whether they sojourn in an agreeable dwelling, or 

 a well-stored larder. Those mollusca which are carnivo- 

 rous, prey on minute animals in a living state, and many of 

 them greedily attack putrid matter. 



The means employed to bring the food within the reach 

 of the organs of deglutition, are exceedingly interesting, 

 both on account of their variety and success. Some are 

 provided with tentacula for securing their prey, and con- 

 veying it to their mouth, as the cuttle-fish ; others protrude 

 a lengthened probosis, or an extended lip or tongue, as the 

 limpet, and thus bring their food into the mouth. By many, 

 however, which are fixed to the same spot during the continu- 

 ance of existence, or only capable of very limited locomotive 

 power, successful efforts are made to excite currents in the wa- 

 ter, whereby fresh portions of it are brought in contact with the 

 mouth, and its animal or vegetable contents separated. 

 Where part only of any kind of food is taken into the mouth 

 at once, the lips are possessed of sufficient firmness to cut 

 off the requisite portions, or there are corneous mandibles 

 to perform the office. 



In the mouth, there is scarcely any process performed 

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

 mals 3 When the food is in the mouth, or entering into the 

 gullet, it is mixed with 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 species the 



