410 rHILOSOl'HY OF ZOOLOGY. 



yond the reach of accurate observation. Tliosc that re- 

 side on land usually shun the light, and creep forth in the 

 evenings to commit their depredations. During warm, dry 

 weather, they stir not from their holes. 



The animals under consideration, feed equally on the 

 products of the vegetable and aninial kingdom. Those 

 which are phytivorous appear to prefer living vegetables, 

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

 that putrid vegetable matter is consumed by them, al- 

 though 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 determine, whether they sojourn in an agreeable dwel- 

 ling, or a well-stored larder. Those mollusca which arc 

 carnivorcms, 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 proboscis, or an extended lip or tongue, and 

 thus bring their food into the mouth. By many, however, 

 which are fixed to the same spot during the continuance of 

 existence, or only capable of very limited locomotive power, 

 successful efforts are made to excite currents in the water, 

 whereby fresh portions of it are brought in contact with 

 the mouth, and its animal or vegetable contents separated. 

 AVhero 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 man- 

 dibles to perform the office. 



In the moutli, tlicrc is scarcely anv process performed 



