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continually changing their situation, must pos- 

 sess distinct organs for seizing and preparing 

 this aliment ; and, hence the necessity in these, 

 more or less constantly, for lips, in some one or 

 other of their numerous modifications ; for cer- 

 tain glands, placed about the mouth, to furnish 

 a fluid by which the dry alimentary matters are 

 lubricated ; for a tongue, or some analogous or- 

 gan ; and, lastly, for jaws and teeth, by which 

 such matters, when hard, are broken down, and 

 reduced to a condition for swallowing. In quite 

 the lowest orders, however, even of these, the 

 mouth and stomach are almost one continuous 

 cavity, the parts of which are indistinguishable 

 from each other ; but, as we advance a little in 

 the scale, the parts become sufficiently obvious, 

 and the office of each is clearly defined. Thus, 

 among the Testacea, the snail has a very perfectly 

 formed mouth, and, in front of it, regular lips, 

 reflected so as to form a small canal within the 

 mouth ; while, in the wared whelk, the lips are 

 elongated into a proboscis, adapted for suction, 

 and capable of being retracted at the pleasure of 

 the animal. Among the Mollusca, the cuttle has 

 a circular fleshy lip, embracing a kind of beak, 

 like that of a parrot ; and the leech one fleshy 

 lip, the orifice of which is triangular, and fur- 

 nished with sharp edges falsely called teeth by 

 which it is enabled to penetrate the skin of ani- 

 mals, preparatory to sucking their blood : its 

 method of sucking is by dilating a large fleshy 

 pouch, called a pharynx, at the back part of the 



