530 Natural History of Molluscous Animals : — 



It must reside, of course, in the mouth ; but, whether diffused 

 over the whole, or Umited 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.* 



3. Smell. — According to Swammerdam, snails have a very 

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

 a little fresh food towards them, for they immediately per- 

 ceived it by the scent, and crept out of their little shells, and 

 came to it." f Gaspard appears to have repeated this experi- 

 ment without success J ; but he is surely hasty in denying, on 

 that account, the existence of the sense, seeing how positively 

 the contrary is affirmed by one of the greatest and most honest 

 of naturalists. Blainville says, in general terms, that the 

 acephalous Mollusca have no smell, but he admits that the 

 Cephalopoda and Gasteropoda possess the sense, and the ter- 

 restrial species in a degree of considerable delicacy, since we 

 observe that slugs and snails seek out particular plants, where 

 sight could not have availed them. According to Cams, it 

 appears to be fully proved by the observation of the aversion 

 of these animals, the Sepiae for instance, from strong-scented 

 plants, that those Mollusca which live partly in water and 

 partly in air have an olfactory organ, but he denies its exist- 

 ence in those which live exclusively in water. § Admitting 

 the existence of the sense in the cephalous families, there 

 remains great uncertainty relative to its seat. Analogy is 

 here at fault, for invertebrate animals have nothing similar to 

 a nose. Cuvier thinks that a special organ may not be neces- 

 sary, for the whole skin appears to resemble a pituitary mem- 

 brane, and may, in consequence, be susceptible of receiving 

 the peculiar impressions emanating from odorous bodies. || 

 If, however, a particular seat for the sense is to be fixed upon, 

 he would place it at the entrance of their pulmonary cavity, 

 because, in all vertebral animals, it is situated at the entrance 

 of the organs of respiration ; an argument of little value in 

 the present instance. Blainville, whose opinion is always 

 entitled to attention, states his belief that the proper tentacula 

 are the olfactory organs, because the skin of them is more 

 ^soft, smooth, and delicate than on any other part, and their 



* Comp. Anat., trans., ii. 694. f Book of Nature, p. 49. 



:j: Zool. Journ., i. 179. § Comp. Anatomy, i. 74. 



11 Comp. Anat., trans., ii. 688. 



