42O THE OCEAN WORLD. 



children those charming ignoramuses who have been taught to 

 repeat the well-known couplet 



" Snail, snail, come out of your hole, 

 Or else I'll beat you black as a coal," 



which finds its counterpart in all European languages. There are 

 two pairs of these tentacles or horns ; one pair quite in front and 

 above, and another smaller and less forward. The first, or upper 

 pair, is distinguished by its size, and also by a black spot or point at 

 their extremity, which are said to be the eye-specks of the snail. 

 These tentacles differ in many respects from the same organs in 

 other molluscs; they are retractile, and can be drawn altogether 

 within the animal into a sort of sheath, by the contraction of the 

 muscles. 



At the anterior extremity of the head we find a sort of plaited 

 opening, which is the mouth ; it is of moderate extent, closed in front 

 by two lips, and armed with two shear-like organs of horny con- 

 sistence, one of them being a sort of rasp, which occupies the place 

 of the buccal cavity, and may be called a tongue ; the other is a 

 median jaw, placed transversely in the membranous walls of the 

 palate, terminating in a free edge, armed with small teeth. This 

 cutting blade, however, executes no movement; but the lingual 

 organ, pressing all alimentary matter forcibly against its lower edge, 

 effects their mastication, and enables it to dispose of fruit, tender 

 leaves, mushrooms, and other substances easily divided. 



At the bottom of the mouth is an oesophagus, or gullet, to which 

 succeeds a stomach of moderate size. The intestine lies in folds 

 round the liver, which is divided into four lobes, and terminates in a 

 special orifice. 



The little lung of the snail is placed in a cavity, vast for its size, 

 just above the general mass of the viscera, and occupies all the last 

 spiral turn of the cavity. 



The mechanism, of respiration is as follows : The animal inhales 

 the air into its lung by forcibly dilating the pulmonary orifice, which 

 lies in the largest spiral turn of the shell. In order to expel the air 

 respired by the lung, it withdraws its body into the narrower part of 

 the shell, where it gathers itself up completely, even to its head and 

 feet, and by this compression of all its little being it expels the air 

 which fills it. These respiratory movements, however, are not 

 regular, but succeed each other only at certain intervals. Life would 

 be too hard for the poor snail were it passed in such violent efforts 

 as would be necessary if it respired as the larger animals do. In its 



