Читать книгу The Book of Shells. Containing the Classes Mollusca, Conchifera, Cirrhipeda, Annulata, and Crustacea онлайн

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8. Tunicata, (enclosed in a case of a leathery consistence.)

9. Vermes, Worms. With lengthened body without divisions; for instance, worms found in the intestines.

10. Radiariæ, (radiated animals,) with the different parts of which they are formed arranged like rays round one common centre; as, for instance, the Star-fish.

11. Polypi, (many feet.) The animal that forms the Coral is a Polypus.

12. Infusoria, (Infusory animals.) These are found in infusions of vegetable substances in water, and are, in general, too small to be visible to the naked eye.

In the present little book we shall treat of the first five of these Classes.

The Molluscous animals are, on account of their organization, placed first among the invertebral animals, a few of the species resembling, in some respects, the more simply-formed fishes.

The systematic arrangement of the Molluscous animals, considered not only as regards their shells, but having reference also to the anatomical distinctions of the creatures themselves, is a modern study. In ancient authors we merely find a few scattered facts, the beauty of the shells attracting their notice more than the value or nature of the animals.