Page:Natural History, Mollusca.djvu/17

From Wikisource
Jump to: navigation, search
This page has been validated.
5
MOLLUSCA.

ficiently expressive, though too uncouth for general adoption, that of Heterogangliata.[1]

All the senses common to the higher animals are found in the Mollusca, though some are, doubtless, wanting in the humbler Classes of the Division. In the Cephalopoda, the organs of sight and hearing are distinct and well developed, and Professor Owen is of opinion that the Nautilus, an animal of this Class, possesses an organ of "passive smell." The Gasteropoda are almost invariably furnished with eyes; and, according to M. Siebold and other zoologists, with ears also, a pair of round capsules, placed near the bases of the tentacles, and enclosing one or more crystalline globules, called otolites. Some of the Conchifera are furnished with numerous eyes, placed among the tentacles, examples of which are found in the Clams and Scallops (Pecten) of our own shores. I scarcely know a more beautiful sight of the kind, than is presented by the edges of the mantle in one of our Scallops. If you ever have an opportunity of procuring a living specimen, which is not difficult to find at low water, on most of our rocky shores, place it in a glass of sea-water, and watch its movements. Soon the beautiful painted shells will begin to open, and the fleshy mantle will be seen to occupy the interval, like a narrow veil extending perpendicularly from each shell. The edge of each of these veils will now be seen, if you examine it with a pocket lens, to be fringed with long white threads, which are the tentacles, or organs of touch; and amongst them lie scattered a number of minute points, having the most brilliant lustre, and bearing a close resemblance to tiny gems. Indeed, the

  1. That is, "having dissimilar nerve-knots."