SENSES — SMELL. 185 



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."* Gaspare! appears to have repeated this 

 experiment without success f ; 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 Cephalopods and Gasteropods 

 possess the sense, and the terrestrial 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 ani- 

 mals, the Sepiae for instance, to strong-scented plants, that 

 those mollusca which live partly in water and partly in air, 

 have an olfactory organ, but he denies its existence in those 

 which live exclusively in water.J 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 necessary, 

 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 nerves more considerable ; || argu- 



* Book of Nature, p. 49. t Zool. Jonrn. i. 179. 



X Comp. Anatomy, i. 74. According to Oppian the Octopus may be 

 induced to leave the sea by placing branches of the olive-tree on the shore ; 

 and Cuvier thinks that this is a statement which deserves to be verified. 

 Hist. des. Sc. Nat. i. 308. § Comp. Anat. trans, ii. 688. 



|| Manuel, p. 107, or more particularly his excellent Principcs d'Anato- 

 mie Comp. i. 341. Dr. Lcidy places the sense, in the terrestrial Gasteropods, 

 in a sort of cul-de-sac, " having its orifice beneath the mouth ; between the 

 inferior lip and the anterior extremity of the podal disk, and which in many 

 species of different genera is elongated backwards into a blind duct, more or 

 less dee]), occupying a situation just above the podal disk within the visceral 

 cavity." This opinion deserves re-examination. — Ann. 8$ Jlfug- N. Hist. 

 xx. 211. — The structure itself had been observed previous toT)r. Leidy's 

 examinations. See p. 170, note §. 



