184 SENSES TASTE. 



being delicately ciliated. Among bivalves a fringe of these 

 filaments is very general. In the genera which have the 

 cloak completely open, as the oysters, and the sea and fresh- 

 water mussels, the filaments fringe it all round ; and in 

 those in which the cloak opens by a tube only, these appen- 

 dices, either simple or variously scalloped, are attached to 

 the circumference of its orifice. Such is the case in the 

 genera Venus, Cardium, &c. 



Now, these tentacula and filaments are exquisitely sen- 

 sitive, and in all likelihood, convey impressions of a more 

 distinct character than the general surface. When the 

 mollusca walk abroad, these organs are all extended to the 

 utmost, and in perpetual motion ; sentinels alive to every- 

 thing around, warning against foe or danger, and watchful 

 of prey. By means of them, the Gasteropods likewise feel 

 their way, and ascertain the nature of the ground they tra- 

 verse, as it seems evident from the manner in which they use 

 them ; but to this purpose the proper tentacula are never ap- 

 plied, at least when they carry the eyes on their tips ; and 

 they appear to be organs of some other sense. If removed, 

 the snail creeps on as if it were unmutilated ; and there are 

 tribes, among which we may instance the entire order of Nu- 

 dibranches, in which their position is such, that they cannot 

 possibly be applied to objects either in front or around them. 



II. TASTE. 



Swammerdam found, by experiment, that snails have 

 " a nice appetite and taste ; " and it seems necessary to 

 suppose the existence of this sense in all mollusca, for they 

 select particular articles of food in preference to others ; and 

 we know no other sense which is fitted to regulate the 

 choice. It must reside, of course, in the mouth ; but, 

 whether diffused over the whole, or limited to a certain 

 space, it were hard to determine. Blainville thinks that in 

 the cephalous mollusca, the seat of taste may probably be 

 in a knob or swelling at the lower end of the buccal cavity ; 

 and Cuvier conjectures that the tentacula, at the orifices at 

 which the water, the vehicle of their aliment, enters, may 

 exercise this sense in the acephalous ones.* 



III. SMELL. 



According to Swammerdam, snails have a very quick 

 smell. " This I observed," says he, " when I moved a 



* Comp. Anat. trans, ii. 694. 



