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differences consists in their possessing lungs and a sanguineous system, or their being destitute of lungs and exsanguineous.
The Linnæan method is, for the most part, built upon this general arrangement of Mr. Ray, especially in regard to quadrupeds; it is, however, an extension of it, and certainly an improvement. That of M. Cuvier, in its subordinate division, is founded upon both these; but in its primary and leading distinctions, upon the nervous or sensorial, instead of upon the respiratory and sanguineous systems; all animals, upon M. Cuvier's scheme, being primarily divided into vertebrated and invertebrated; those furnished with a back-bone, or vertebral chain, for the purpose of enclosing the spinal marrow, and those destitute of such a chain: the secondary sections, consisting of vertebrated animals with warm blood, and vertebrated animals with cold blood; invertebrated animals with blood-vessels, and invertebrated animals without blood-vessels.
All these, under his last modification, which is that subjoined to his Leco tures on Comparative Anatomy,* are regarded as embracing nine distinct classes; as, I. MAMMALS; and, II. BIRDS, which belong to the warm-blooded vertebral division. III. AMPHIBIALS; and, IV. FISHES, which belong to the coldblooded vertebral division; and the five following, which fill up the division of invertebral animals : V. MOLLUSCOUS, soft-bodied marine animals, or mostly marine animals, as oysters, limpets, whelks, cuttle-fish, pipe-worms or shipworms, defended by a testaceous covering: VI. CRUSTACEOUS; as crabs, various lobsters, shrimps, sea-spiders, and the monoculus tribes. VII. INSECTS; being all those ordinarily so denominated. VIII. WORMS ; embracing, along with those commonly so called, leeches, and various sea-worms with bristles on the sides of the body, as aphrodites, terebels or naked ship-worms, serpules, amphitrites, nereids, tooth-shells. IX. ZOOPHYTES; the term being used very extensively, so as to include, not only all the zoophytes or plant-like animals of Linnæus and other naturalists, but all their infusory, wheel, or microscopic animals; their medusas or sea-nettles, actinias or anemonies, and other efflorescent worms, urchins, and star-fishes; and thus largely infringing on the molluscous order of prior arrangements.
Many of these classes have inferior sections and subsections, under which the genera that appertain to them are respectively marshalled. But in a general outline it is not necessary to follow up the arrangement more minutely.
The common classification of zoological writers of the present day is still that of Linnæus ; and as such, it is that which I shall regularly follow up in the remainder of the present study, as being best adapted to popular purposes. It is probable, however, that the classification of Cuvier will ultimately take the lead of it; it is somewhat more abstruse, but considerably more definite; and offers a noble specimen of scientific ingenuity, applied to one of the noblest branches of scientific study; and I shall hence advert to this classification as we proceed, for a comparison with that of the justly celebrated Swedish naturalist.
The Linnæan system of zoology divides all animals into six classes, and each class into a definite number of orders; every order consisting of an indefinite number of kinds or genera; and every kind or genus of an indefinite number of species: the individuals in each species being perhaps innumerable.
The six classes are as follows: I. mammals, or suckling animals ; II. birds; III. amphibials ; IV. fishes; V. insects; VI. worms.
These may be contemplated either in an ascending or a descending scale. As we have begun with brute matter, and have progressively pursued it from a shapeless mass to mineral crystallization, from mineral crystallization to vegetable organization, and from vegetable organization to animal spontaneity, it will be most congruous still to continue in the same direction, and to commence with the lowest class constituting the worm tribes.
I. WORMS, in the Linnæan vocabulary, is a term of far more extensive
* Leçons d'Anatomie Comparée de G. Cuvier, 8vo. 4 tom. Paris, 1805.
import than in its popular signification; and the reason of this we shall perceive as we proceed. They include all animals below the rank of insects, and are classically characterized, as being mostly without distinct head and without feet; the most prominent organ being their tentacles or feelers. The class is divided into FIVE ORDERS; intestinal, molluscous, testaceous, zoophytic, and infusory.
The FIRST ORDER OG INTESTINAL, with a few exceptions which are found in the waters, consists of animals that are uniformly traced in the bowels of the earth, or of other animals; whence, indeed, their ordinal name. They are ordinarily characterized as being simple, naked animals, without limbs. I shall instance as examples of it, the ascaris, which is found so frequently in the intestinal tube of mankind, in the species of maw or thread-worm, and round-worm: the tænia, which comprises among many others the two species of tape-worm and hydatid; and the filaria or Guinea-worm, which inhabits both the Indies, and is frequent in the morning dew; at which time it winds unperceived into the naked feet of slaves, or other menials, and creates the most troublesome itchings, frequently accompanied with inflammation and fever. The only method of extracting it is to draw it out cautiously by means of a piece of silk tied round its head as it peeps from the inflamed surface; for if, in consequence of too much straining, the animal should break, the part remaining under the skin will still survive, grow with redoubled vigour, and occasionally augment the local inflammation to such an extent, as to prove fatal. It is often twelve feet long, though not larger in diameter than a horse-hair.
The next intestinal worm at which it is worth while to throw a glance as we pass on, is the fasciola or fluke, principally known from one of its species being found in large abundance in the liver of sheep during the disease called the rot, but whether the cause or the result of this disease has never yet been sufficiently ascertained. There are other species of this animal found in the stomach, intestines, or liver of various other animals, and occasionally of man himself. The fasciola is hermaphrodite and oviparous.
The gordius or hair-worm is chiefly worthy of notice as being supposed, in one of its species, if incautiously handled, to inflict a bite at the end of the fingers, and produce the complaint called a whitlow. It inhabits soft stagnant waters, is from four to six inches long, and is almost perpetually twisting itself into various contortions and knots.
The last two kinds I shall enumerate under this order of worms are, the lumbricus or earth-worm, including the dew-worm and the slug; and the hirudo or leech, both of them too well known under several species to require any farther remark in the present rapid outline. This order includes nearly the whole of M. Cuvier's class of worms, with the exception of his sea-worms, already adverted to.
The SECOND ORDER of the WORM CLASS is denominated MOLLUSCA, MOLLUSCOUS, or soFT-BODIED SHELL-WORMS ; and consists, for the most part, of similar animals to those found in snail, oyster, nautilus, and other shells, but without a shelly defence : and hence, in their ordinal character, they are described as simple animals, naked, but furnished with limbs, of some kind or other. By this last mark they are distinguished from the preceding, or intestinal order, which, as already observed, consists of simple animals, naked and destitute of limbs. To place the order more immediately before you, I shall select a few examples from those animals that are most familiar to us, or are most remarkable for the singularity of their structure or other properties.
The limax or slug is one of the most simple animals that belong to this order: its only limbs are four feelers, tentacles, or horns, as they are commonly called, situate above the mouth, with a black dot at the tip of each of the larger ones, which is supposed to be an eye, though this point has not been fully established. Another genus of molluscous worms is the terrabella; one species of which is the ship-worm, with an oblong, creeping, naked body, and numerous capillary feelers about the mouth, from four to six inches in length. It is sometimes enclosed in a testaceous or shelly tube, and is then
called termes, pipe-worm, or shelly ship-worm, and belongs to the next order. In both forms it is peculiarly destructive to shipping; boring its way into the stoutest oak planks, with great rapidity and facility; and chiefly forming necessity for their being copper-bottomed. The animal is, in its habits, gregarious; and hence, in attacking a vessel, it advances in a multitudinous body, every individual punctiliously adhering to its own cell, which is separated from the adjoining by a partition not thicker than a piece of writing-paper. In a preceding lecture, however, 1 had occasion to observe, when glancing at the shelly ship-worm, or leredo navalis, that, by its attacking the stagnant trunks of trees and other vegetable materials, that in many parts of the world are washed or thrown down by torrents and tornadoes from the mountains, and block up the mouths of creeks and rivers, and thus powerfully contributing to the dissolution of dead vegetable matter, it produces far more benefit than evil; the benefit being universal, but the evil partial and limited. In 1731 and 1732 they appeared in great numbers on the banks of Zealand, and considerably alarmed the Dutch, lest the piles by which these banks are supported should have been suddenly destroyed. They never, however, staid long enough to commit mischief, the climate, perhaps, being too cold for them.
Another genus worthy of notice under this order is the actinia, which includes those species of naked sea-worms which are vulgarly called sea-daisy, actinia Bellis ; sea-carnation, a. Dianthus ; sea-anemony, a. Anemonoides ; and sea-marigold, a. Calendula ; from their resemblance to the steins and flowers of these plants. The first three are found on the warmer rocky coasts of our own country, as those of Sussex; and the last on the shores of Barbadoes. The sea-carnation is sometimes thrown upon our flat coasts, and left evacuated of its water by the return of the tide ; in which case it has the appearance of a slender, long-stalked, yellow fig.
Most of us are acquainted with some species of the sepia or cuttle-fish, which is another genus of the order before us. The common cuttle-fish, sepia officinalis, is an inhabitant of the ocean, and is preyed upon by the whale and plaise tribes ; its arms are also frequently eaten off by the conger-eel, but are reproducible. The bony scale on the back is that alone which is usually sold in the shops, under the name of cuttle-fish, and is employed in making pounce. These animals have the singular power, when pursued by an enemy, of squirting out a black fluid or natural ink, which darkens the waters all around, and thus enables it to escape. This natural ink forms an ingredient in the composition of our Indian inks. The worm or fish was formerly eaten by the ancients, and is still occasionally used as food by the Italians. In hot climates, some of the species grow to a prodigious size, and are armed with a dreadful apparatus of holders, furnished with suckers, by which, like the elephant with its proboscis, they can rigidly fasten upon and convey their prey to the mouth. In the eight-armed cutile-fish, sepia octopodia, which inhabits the Indian seas, the arms or holders are said to be not less than nine fathoms in length. In consequence of which the Indians never venture to sea without hatchets in their boats to cut off these monstrous arms, should the animal attempt to fasten upon them, and drag them under water. This genus, with that of the argonauta and nautilus, constitute the order CEPHALOPODA of Cuvier, which belongs to his class named MOLLUSCÆ.
The medusa is another genus entitled to attention, as affording various spe. cies that shine with great splendour in the water. The worms of this kind are vulgarly denominated sea-nettles, and consist of a tender gelatinous mass, of various figures, furnished with arms or tentacular processes, issuing from the under surface. The larger species, when touched, produce in the hand a slight tingling and redness, and hence, indeed, the name of sea-nettles, by which they are commonly distinguished. A few of the species are found on our own coasts ; but by far the greater number are exotics.
The asterias, sea-star, or star-fish, is another genus of molluscous worms, and, in some of its species, is known to all of us. The most curious species of this genus is the asterias Caput Medus@, or basket-fish; which inhabits most seas, and consists of five central rays, each of which divides into two
smaller ones, and each of which smaller ones again divides into two others ; the same kind of division and subdivision being continued to a vast extent, and every ray regularly decreasing in size, till at length the ramifications amount to many thousands, forming a beautiful net-work spread over the water. The colour of the worm varies : being sometimes pale, sometimes reddish-white, sometimes brown.
The only other genus I shall mention under this order is the echinus, seaurchin, or hedgehog : its species are very numerous, and of a great multiplicity of forms, globular, oval, shield-like, and heart-shaped. Many of them appear to have long since become extinct, and are only to be found in a state of petrifaction. The surrounding spines form an admirable coat of mail when perfect; but they are generally broken off from the shell when it is picked up empty on our own coasts.
The THIRD ORDER of the Linnæan class of WORMS are called TESTACEA or TESTACEOUS; and comprise those that are surrounded with a shelly or testaceous covering. They are of three kinds ; those possessing a single shell, of whatever form or kind, and hence denominated univalves ; those possessing two shells, which are called bivalves or conchs ; and those possessing more than two shells, which are in consequence named multivalves.
The UNIVALVES, or SINGLE-VALVED, are the most numerous, and exhibit the greatest variety of forms. For the most part they are regularly or irregularly spiral : among the most common of them may be mentioned the helix or snail-genus; the patella or limpet; and the turbo or wreath-genus, of which the periwinkle is a species; the animal in all which is a limax or slug. Among the more curious are, the murex or purple-shell so highly valued by the ancients for the exquisite dye it is capable of producing; the volute or mitre, including those fine polished spiral shells, without lips or perforation, which so often ornament our chimney-pieces, sometimes embellished with dots, and at other times with bands of colours of various hues; the strombus, comprising the larger shells appropriated to the same purpose, spiral like the volute, but with a large expanding lip spreading into a groove on the left side, and often still farther projecting into lobes or claws, the back frequently covered with large warts or tubercles, in some species called coromant's foot; in all which, the animal or inhabitant is still a limax or slug; and the nautilus and argonauta, the pearl-nautilus and paper-nautilus; the first of which is lined with a layer of a most beautiful pearly gloss, and in the East is manufactured into drinking-cups ; and the second of which is remarkable for its exquisite lightness, and the rumour common to most countries of its having given to mankind the first idea of sailing. In reality, it sails itself, and with exquisite dexterity; and to this end the animal that is usually found inhabiting the shell, and which, till of late, was supposed to be a four-armed cuttle-fish, though now regarded as an ocythoe, by Dr. Leach named o. Cranchii, in memory of the indefatigable, but unfortunate, Cranch of the British Museum,* as soon as it has risen to the surface, erects two of its arms to a considerable height and throws out a thin membrane between them, thus producing a natural sail; while the oars or rudder are formed by the other two arms being thrown over the shell into the water, by which ingenious contrivance, or rather instinctive device, the paper-nautilus sails along with considerable rapidity. M. Cuvier has separated the nautilus from the rest though distinctly a univalve; and, as we have already noticed, has united it with the cuttle-fish, under an order of MOLLUSCÆ, which he calls CEPHALOPODA. The ordinal name for the others is with him GASTEROPODA, as most of them crawl on their bellies, and carry the shell over them as a shield. They have a distinct and moveable head, by which they essentially differ from our next order, which are without a distinct head of any kind. The two sexes are united in the same individual, but require a reciprocal union for breeding.
The BIVALVED or TWO-SHELLED TESTACEOUS WORMS, the acephala or headless of Cuvier, are best explained by referring you to the oyster and the muscle
Series 1. Lecture xi. p. 118.
(ostrea and mytilus), both which contain species that produce pearls, and mother-of-pearl; though the real pearl-muscle is amya or gaper, found chiefly on the coasts of Malabar and Ceylon, where the principal pearlfisheries are established. The species of oyster that produces small pearls is sometimes traced on our own shores, and is said to have been at one time frequent in the river Conway, in Wales. Most of the oysters cast their spawn towards the close of the spring, or in the beginning of the summer, as the month of May. This spawn is by the fishermen called spat, and in size and figure each resembles the drop of a candle. As soon as cast or thrown off, these embryon disks adhere to stones, old oyster-shells, pieces of wood, or whatever other substance comes in their way; a calcareous secretion issues from the surface of their bodies, and in the course of twenty-four hours begins to be converted into a shelly substance. It is two or three years, however, before they acquire their full size.
The scallops, which are a tribe belonging to the oyster kind, are capable of leaping out of the water at pleasure, to the distance of half a yard: when elevated they open their shells, and eject the water within them, and then falling back into the water close them with a loud snap.
Among the more elegant of this division is the nacre, pinna, or sea-pen, so called from its form; the animal of which (a limax or slug) secretes, as we have already observed, a large quantity of fine strong silky hair, or beard, which by the Italians is woven into a kind of silky plait. And among the most extraordinary is the gigantic chama or clamp-shell, in form resembling the oyster: one species of which we noticed not long since, as found in the Indian Ocean, of the weight of between five and six hundred pounds; the fish or inhabitant large enough to furnish a hundred and twenty men with a full meal, and strong enough to lop off a man's hand, and cut asunder the cable of a large ship.
Of the MULTIVALVED TESTACEOUS WORMS, or those containing more than two shells, there are but three known species, the chiton, the lepas or acorn-shell, and the phloas, or, as it is often improperly called, pholas, so denominated from its secreting a phosphorescent liquor of great brilliancy, which illuminates whatever it touches or happens to fall upon, and to which Linnæus chiefly ascribed the luminous appearance which the sea often assumes at a distance: a subject, however, which we shall have occasion to examine hereafter.
The FOURTH ORDER of the Linnæan class of WORMS is called ZooPHYTES, or PLANT-ANIMALS, so denominated from their efflorescing like plants. Most of them are of a soft texture, as the hydra or polype, so well known from its being capable of existing when turned inside out, and of reproducing any part of its tentacles or body when destroyed by accident. Some are corky or leathery, as different species of the alcyonium; some bibulous, as the spongia or sponge, which is now decidedly ascertained to be an animal substance; and some calcareous, as the numerous families of coral, which, under the form of tubular, starry, or stony stems, are denominated tubipores, madrepores, and isises.
The Fifth or INFUSORY ORDER OF WORMS, comprehends those minute and simple animalcules which are seldom capable of being traced, except by a microscope; and, for the most part, reside in putrid infusions of vegetables, or in stagnant waters filled with vegetable matter. Of these, the smallest known species is denominated monas. To a glass of the highest magnifying power it appears nothing more than a minute simple point or speck of jelly, obviously, however, evincing motion, but often from its delicacy seeming to blend itself with the water in which it swims.
Such is a bird's eye view of the Linnæan class of worms, and its five orders of intestinal, molluscous, testaceous, zoophytic, and infusory animals.
The INSECTS form the NEXT CLAss in an ascending scale; classically characterized as small animals, breathing through lateral spiracles, armed on all sides with a bony skin, or covered with hair; furnished with numerous feet and moveable antennæ or horns, which project from the body, and are