in Natural History, a name given by Linnaeus to petrified bodies resembling worms.

Of these he reckons four genera. 1. Petrified lithophyta. 2. Petrified shells. 3. Petrified zoophytes. 4. Petrified reptiles.

INTRODUCTION.

Under this head we propose to give the natural history of those animals which Linnaeus has arranged under the class of VERMES, forming the last class of the animal kingdom. The title which we have adopted for this article is derived from the Greek ἰχθύς, an earthworm, and λόγος, a discourse.

In this article we are to consider, not only those animals which are commonly known by the name of worms, but all those which have the same general character of being slow in motion, of a soft substance, extremely tenacious of life, capable of reproducing such parts of their body as may have been taken away or destroyed, and inhabiting moist places.

Linnaeus has divided the class into five orders.

1. Integmina, consisting of animals which are very simple in their structure, and most of which live within other animals; such as the worms which infest the intestines of man, quadrupeds, &c., though many of them are found in moist clay, and other damp situations.

2. Mollusca, containing such animals as have naked Mollusca bodies, or are not furnished with shells, but are provided with tentacula or arms, being mostly inhabitants of the sea.

3. Testacea, 3. *Tetacea*, differing from the former in little more than their being furnished with calcareous, flaky coverings, which they carry about with them, constituting the great variety of shell-fish, snails, &c.

4. *Zoophyta*, containing such creatures as seem to bear a resemblance both to plants and animals; being fixed to one place by a foot or root, and shooting up into items like plants, but possessing besides the powers of animation, and partially of locomotion.

5. *Infusoria*, comprising those animated beings generally called *animalcules*, that are found in most watery liquors; especially in the infusions of vegetable substances.

Of these five orders, only four fall to be particularly considered in this article, the *Tetacea* having been already fully treated of under *Conchology*.

The animals which we are about to describe are generally considered as the lowest in the scale of animated beings. The simplicity of their form, the humility of their station, and the low degree of sense and motion which most of them enjoy, render them an object of little attention to mankind in general, excepting in so far as they contribute to the supply of their wants, or render themselves formidable, by the pain and distress which they occasion to those bodies which nature seems to have destined for their habitation. But to the eye of the naturalist, every part of nature becomes interesting, and this humble class of beings has, in later times, attracted a considerable share of attention.

Still, however, this part of natural history is much more imperfect than any other, and so it will probably long remain, partly from the difficulty of prosecuting our enquiries, and partly from the little interest which a superficial observation of many of these animals is calculated to excite. It will not be thought extraordinary that they are less known than other animals, when we consider, that the examination of them does not offer so many allurements as that of insects, birds, and the more showy part of the animal creation, and is besides impeded by much greater difficulties. Many of them cannot be obtained without diving to the bottom of the sea, or braving pain and danger in the pursuit. The *Furia infernalis* attacks the searcher in the marshy plains of Bothnia, and the *Sepia octopus* stretches forth his gigantic arms, to entangle and drag him to his watery den. Hence the opportunities of examination are often rare; and from the changes which many of the species undergo, we cannot always be certain whether one which we may meet with hereafter be a new species, or one which we have seen before.

This circumstance has occasioned several varieties to be described as distinct species, and the same species to be repeated under different names, to the great confusion of the naturalist. Again; the confusion of their bodies is, in many cases, so soft, that they can scarcely be preferred in our cabinets, and thus the observer is deprived of one of the chief sources of information and reference, which, in other departments of the science, is so well calculated to assist his studies.

The study of helminthology, however, holds out many inducements to the admirer of nature's works, as stages at it affords an ample field for the gratification of his curiosity, and may even be rendered subservient to the advancement of more solid and useful knowledge.

If we consider the number of animals, which naturalists have included under the general name of worms; if we observe the simplicity of form in some of them, and the complicated structure of others; in fine, if we reflect on the various modes in which they are propagated, and on the surprising faculty, which many of them possess, of spontaneous reproduction: the imagination will be astonished with their number and variety, and confounded by their wonderful properties. The waters are peopled with myriads of animated beings, which, though invisible to our unassisted eyes, are endowed with organs as perfect as the largest animals, since, like these, they reproduce their like, and hold in the scale of nature a rank as little equivocal, though less obvious and obtrusive. The elegance of form and beauty of colour, which some of the *mollusca* and *zoophyta* possess, must render them an object of admiration to the most indifferent observer.

The physiologist will derive considerable assistance in explaining some obscure functions of the animal economy, from a comparative view of them in this humble class of beings; while the physician, by acquiring a knowledge of the habits of such of them as infect the bodies of man, will be the better able to ascertain their presence, expel them from their habitation, or counteract their effects. The geologist, though he cannot admit the hypothesis of Buffon, that all the limestone of this earth has been formed from the relics of corals and shell-fish, will yet here trace the origin of many of the secondary strata, and from the wonderfully rapid production of coral reefs, which we shall notice towards the conclusion of this article, will find little difficulty in accounting for the evolution of new land from the bosom of the deep.

We shall divide the sequel of this article into two chapters, the first of which will contain a general view of the classification of the genera, and in the second will be given the classification and natural history of the species. The latter will be sub-divided into four sections, corresponding to the four orders of *intestina*, *mollusca*, *zoophyta*, and *infusoria*. As we are able to devote but a small portion of our work to this subject, we shall confine any particular description to those species which are of most importance; and to relieve the tediums of systematic arrangement, we shall mention everything worth notice under the genus or species then under consideration. LINNAEUS, whose extensive genius has displayed itself so eminently in almost every department of natural history, has, perhaps, failed more in this part of the science than in any other. In the earlier editions of the Systema Naturae, the individuals described are comparatively few, and the characters of many of them are imperfect or erroneous. These imperfections must be attributed to the small progress which helminthology had made in the beginning of last century, as the discoveries of succeeding naturalists have contributed not only to increase the number of genera and species far beyond what were known at that time, but also to improve their distinguishing characters.

M. Brugiere, to whom this part of the Encyclopedie Methodique was allotted, made several alterations in the arrangement of Linnaeus, whose general classification he has followed in the tabular view of the subject prefixed to the plates of helminthology. M. Brugiere's work is entitled to much praise, and it is to be regretted that he did not live to complete his undertaking.

The arrangement of these animals given by Cuvier, is in great esteem on the continent, and will probably, when fully completed by future discoveries of that celebrated naturalist, supercede the Linnean classification. Cuvier has given a tabular view of his classification, at the end of the first volume of his Comparative Anatomy, and a more detailed account in his Tableau Elementaire d'Histoire Naturelle. He arranges the vermes of Linnaeus under three heads; MOLLUSCA, WORMS, and Zoophytes. The following is a translation of the tables.

I. MOLLUSCA.

A. Head furnished with Tentacula that serve for Feet.

Family 1. CEPHALOPODA.

a. Naked.

SEPIA, comprehending the sepia, loligo, and octopus.

b. Testaceous.

ARGONAUTA. NAUTILUS.

B. Head free; and crawling on the belly.

Fam. 2. GASTEROPODA.

a. Having no shell, or having the shell concealed by the flesh.

CLIO. SCYLLÆA. DORIS. TRITONIA. ÆOLIA. PHYLLIDIA. THETIS. LIMAX. TESTACELLA. SEGARETUS. APLYSIA.

b. With an apparent Shell.

a. In several pieces. Multivalves.

CHITON.

β. Conical. Conivalves.

PATELLA, comprehending fissurella, patella, crepidula, and calyptraea.

γ. Spiral. Spirivalves.

ι. With the Aperture entire.

HALYOTIS. NERITA, comprehending nerita and narica. TURBO, comprehending turbo, cyclophora, and turretella.

VERMITUS.

TROCHUS, comprehending pyramidalis, trochus, monodonta, and solarium.

BULLA. HELIX, comprehending planorbis, helix, ampullaria, mellania, bulimus, achatina.

2. With the Aperture sloped towards the bottom.

VOLUTA, comprehending voluta, mitra, columbella, marginella, ancilla, and oliva.

OVULA. CYPRÆA. CONUS. TEREBELLUM.

3. With the Aperture ending in a Canal.

MUREX, comprehending cerithium, pleurotoma, fusus, fascicularia, pyrula, murex, and turbinella.

STROMBUS, comprehending strombus, pterocera, and rostellaria.

BUCCINUM, comprehending cassidea, harpa, buccinum, terebra, purpura, and nassa.

C. Having no distinct Head.

Fam. 3. ACEPHALA.

a. Having no Shells, but furnished with a membranous leathery cloak.

ASCIDIA. SALPA. PTEROTRACHEA. THALIA.

b. With a cloak, and furnished with Shells.

α. Open anteriorly, having no reticulated Feelers, nor ciliated arms.

1. Inequivalves.

OSTREA. LAZARUS. SPONDYLUS. PLACUNA. ANOMIA. PECTEN.

2. Equivalves. Chap. I.