Imágenes de página
PDF
ePub

so rapidly and dexterously will they destroy, in less bodies, food, furniture, books, clothes, and timber of whatever magnitude, leaving in every instance the merest thin surface, that a large beam will in a few hours be eaten to a shell not thicker than a page of writing paper.

It was my intention to have finished our survey of the Linnaaan system in the course of the present lecture; but the prospect swells so widely before us that it is impossible; and the remaining four classes of fishes, amphibials, birds, and mammals must be reserved for another study.

In the mean time, allow me to remark, that low and little as the tribes we have thus far contemplated may appear, they all variously contribute to the common good of animal being, and aid, in different ways, the harmonious circle of decomposition, renovation, and maturity of life, health, and enjoyment. The insect tribes, beautiful as they are in their respective liveries, may be regarded as the grand scavengers of nature. Wherever putridity is to be found, they are present to devour the substance from which it issues; and such is the extent and rapidity of their action, that it has been calculated by some naturalists that the progeny of not more than a dozen flies will consume a dead carcass in a shorter space than a hungry lion. Thus, while they people the atmosphere they purify it; and in many instances, perhaps, and by tribes invisible to the naked eye, purge it of those noxious particles with which it is often impregnated, and which, at certain seasons, are apt to render it pestilential.

The indefatigable labour of the worm-tribes in promoting the general good is still more striking and manifest. The gordius or hair-worm perforates clay to give a passage to springs and running water; the lumbricus or earthworm pierces the soil that it may enjoy the benefit of air, light, and moisture; the terebella and terredo, the naked ship-worm and the shelly ship-worm, penetrate dead wood, and the phloas and mytilus, rocks, to effect their dissolution; while the termes or white ant, as we have just observed, attacks almost every thing within its reach, animal, vegetable, or mineral, with equal rapacity, and reduces to its elementary principles whatever has resisted the assault of every other species. The same system of warfare is, indeed, pursued among themselves; yet it is pursued, not from hate, as among mankind, but from instinct, and as the means of prolonging and extending as well as of diminishing and cutting short the term of life and enjoyment.

It has often been urged against the goodness, and sometimes against the existence, of the Deity, that the different tribes of animals are, in this manner, allowed to prey upon one another as their natural food, and that a large part of the globe is covered with putrid swamps, or wide inhospitable forests, or merely inhabited by ravenous beasts and deadly serpents.

Presumptuous murmurers! and what would your wisdom advise, were Providence to consult you upon so glaring an error? Would you then leave every rank of animals to perish by the mere effects of old age? With the example so often before you of the misery endured by a favourite horse or a favourite dog when suffered to drain out the last dregs of existence in the midst of ease he cannot enjoy, and of food he cannot partake of,—a misery which often compels us, as an act of mercy, to anticipate his fate, even at last, by the aid of violence,—would you abandon every animal to the same wretchedness, only a hundred-fold multiplied by the horrors of want and hunger, which he must, by growing every day more infirm, be every day growing more incapable of appeasing?—Or would you cut short the evil at once, by destroying death itself, and thus rendering every animal immortal? They would not thank you for such an interference, nor applaud the vain benevolence that might dictate it; an interference which, by preventing the necessity for offspring, would extirpate from the animal frame its best feelings; which would extinguish the wise and harmonious distribution into sexes; and make an equal inroad on the pleasures of sense and the endearments of instinct.

It is granted, that a great part of the globe is an inhospitable wilderness; that it consists, to a considerable extent, of waste inaccessible jungle overrun by rapacious beasts and reptiles, of putrid swamps crowded by myriads of venomous insects, and of immense warrens burrowed by countless hordes of the hampster, the mole-rat, and the white ant. Even here, however, wherever life exists, it exists to those that possess it as an enjoyment j while these very scenes and these very animals only fill up what man has no occasion for, and equally and instantly disappear as soon as he presents himself, and exercises that industry and ingenuity which alone constitute his authority; and upon which alone his health and his happiness are made to depend.

But this is not all.—While in their different gradations these outcasts from man are thus enjoying life themselves, they are preparing, in the best manner possible, the various tracts they occupy for his future use and habitation. The soil that supports us, and gives us our daily bread, is nothing but a mixture of animal and vegetable materials; other substances, indeed, enter into it, but the great, the important, the active, and leavening constituent is of an organized origin. These materials, then, are perpetually forming and accumulating, and rising into an unbounded and inexhaustible storehouse of subsequent riches and plenty by the alternate generation and decomposition of the different kinds and orders of plants and animals which thus fill up, and, as we are apt to believe, encumber the regions we are contemplating; regions which, though in our own day unexplored or abandoned both by savage and civilized man. may, in that revolution of countries and of governments which is perpetually passing before our eyes, become, in some future period, the seat of universal dominion, the emporium of taste and elegance, of virtue and the sciences. So the fairest fields of Rome were formed out of the putrid Pontine marshes, and England has become what she is, from being a land of bogs and of blights, of wolves, wild boars and gloomy forests.

f

LECTURE H.

-OS ZOOLOGICAL SYSTEMS, AND THE DISTINCTIVE CHARACTERS OF ANIMALS. (The subject continued.)

In our last lecture we took a momentary glance at the history of zoology as a science, noticed the primary features of the best methodical arrangements to which it has given rise, and made some progress towards a brief delineation of that of Linnaeus, which still takes the lead amid the writers of the present day, and is hence chiefly entitled to attention in a course of popular study, generally collating it, however, with that of M. Cuvier, as we proceeded.

We observed that the Linnaean system comprehends all animals of every description whatever, under the six classes of mammals, birds, amphibials, fishes, insects, and worms. We pursued this arrangement in an ascending scale, as most consistent with the plan adopted at the opening of the present course of instruction; and commencing with the class of worms, finished with that of insects. It remains for us to prosecute the same rapid outline of inquiry through the four unexamined classes of fishes, amphibials, birds, and mammals.

Fishes are classically characterized in the Linnaean system as being always inhabitants of the water; swift in their motion, and voracious in their appetite; breathing by means of gills, which are generally united by a bony arch; swimming by means of radiate fins, and for the most part covered over with cartilaginous scales.

The class is divided into six orders; the ordinal characters being taken from the position of the ventral or belly fins, or from the substance of the gills. The orders are, apodal, fishes containing no ventral or belly fins; jugular, having the ventral fins before the pectoral; thoracic, having the ventral fins under the pectoral; abdominal, having the ventral fins behind the pectoral. In all these four, the rays or divisions of the gills are bony. In the fifth order, which is called branchiostegous, the gills are destitute of bony rays; and in the sixth, or chondropterygious order, the gills are cartilaginous; all which will be easiest explained by a few familiar examples. Into the general divisions of this class M. Cuvier has introduced no change of any importance whatever, his own sections and names running parallel with those of Linnaeus.

The kind best calculated to elucidate the First or Apodal Order, is the well known muraena or eel; since every one must have noticed, that this fish has no ventral or, indeed, under-fins of any kind. In many of its species, it has a very near approach to the serpent tribes; insomuch that several of them are called sea-serpents, and by some naturalists are described as branches of the serpent genus. Even our own common eel, muraena Anguilla, is often observed to quit its proper element during the night, and, like the snake, to wander over the meadows in search of snails and worms. The next genus I shall mention is the gymnotus, of which one species, gymnotus electricus, is the electric eel, an inhabitant of the rivers of South America, from three to four feet long, and peculiarly distinguished by its power of inflicting an electrical shock, so severe as to benumb the limbs of those that are exposed to it. The shock is equally inflicted whether the fish be touched by the naked hand, or by along stick. It is by this extraordinary power, which it employs alike defensively and offensively, that the electric eel escapes from the jaws of larger fishes, and is enabled to seize various smaller fishes as food for its own use. There are, however, a few other fishes, as we shall have occasion to notice in proceeding, that possess a similar power, as the torpedo of European seas, and especially of the Mediterranean, and the electric silurus of those of Africa.

The only other genus it will be necessary to glance at under this order, is the xiphias or sword-fish; so denominated from its long sword-like and serrated snout, with which it penetrates and destroys its prey. Its chief species is found in the Mediterranean and other European seas, sometimes not less than twenty feet long; is very active, and, in one instance, has been known to attack an East Indiaman with so prodigious a force, as to drive its sword or snout completely through the bottom of the ship, and must have destroyed it by the leak which would hereby have been occasioned, had not the animal been killed by the violence of its own exertion; in consequence of which, the snout remained imbedded in the ribs of the ship, and no leak of any extent was produced. A fragment of this vessel, with the sword imbedded in it, has been long lodged as a curiosity in the British Museum.

The Jugular Order of fishes, distinguished by the ventral or belly fins being placed before the pectoral or chest fins, is the next in succession, and contains only six separate kinds; of which the two most familiar to our own country are the gadus or codfish, including, among a variety of other species, the haddock, whiting, and ling; and the blenniusorblenny, including several species of the hake. In these the ventral or belly fins are advanced so far forward, as to be immediately under the jole.

Of the Third or Thoracic Order, in which the ventral fins lie somewhat backwarder, and directly under the pectoral or chest fins, I may instance, among those most familiar to us, the zeus or John doree; the pleuronectes, including the numerous families of plaice, flat-fish, flounder, sole, turbot; the eyes of all which are situate on the same side of the head, in some species on the left side, in others on the right, but always on one side alone: the perca or perch, one species of which, perca scandens, has a power, like the eel, of quitting the water, and climbing up trees, which it effects by means of the spines on its gill-covers, and the spinous rays of its other fins; and the gasterosteus or stickle-back. Among the more remarkable or curious kinds, I may mention the echeneis, remora, or sucking-fish, which inhabits the Mediterranean and Pacific seas; and though only from twelve to eighteen inches long, adheres so firmly to the sides of vessels and of larger fishes, by its head, that it is often removed with great difficulty; and was, by the ancients, supposed to have the power of arresting the motion of the ship to which it adhered. I may also mention the chaetodon rostratus, beaked or rostrate chaetodon, an inhabitant of the Indian seas, which curiously catches for its food insects that are flying over the surface of the sea, by ejecting water from its tubular snout with so exact an aim as to strike and stun them with the greatest certainty, and hereby to bring them down into its jaws.

The Fourth Order of the Linnaean class of Fishes, is called Abdominal; in consequence of having the ventral or belly fins placed considerably more backward, and behind the pectoral or chest fins: and here, as in all the preceding, the gills are bony. The salmo or salmon, with its numerous families of trout, smelt, char, and grayling; the esox or pike, including the gar-fish; the clupea or herring, which, as a genus, comprises the pilchard, sprat, and anchovy; the cyprinus or carp, including the gold-fish, gudgeon, tench, and a variety of similar species; the mugil or mullet; are among the more familiar kinds of this extensive order.

Of these, the herring is one of the most remarkable, from its migratory habits; and the carp, from its great longevity, having in many instances been known to reach more than a hundred years of age; and from its facility of being tamed and made to approach the edge of a fish-pond on the sound of its dinner-bell, and to eat crumbs of bread out of a man's hand.

But amid the most singular of the kinds belonging to this order is the exocoetus or flying-fish, which, though occasionally traced in other seas, is chiefly found between the tropics, and has a power, by means of its long pectoral fins, of raising itself out of the water and continuing suspended in the air till these fins become dry; by which means it effectually avoids the jaws of such predatory fishes as are in pursuit of it. But unhappily it is often seized at the same time by the talons of ospreys, sea-gulls, or some other rapacious birds that are perpetually hovering over the water to take advantage of its ascent. There are, however, various other fishes that have a similar power of flight or suspension, and from a similar cause, but none in so complete a degree. It is to this curious power Dean Swift makes allusion in the following lines:—

"So fishes, rising from the main,

Can soar with moisteu'd wings, on high:
The moisture dried, they sink again,
And dip their wings again to fly."

The Fifth Order Of Fishes is denominated Brakchiosteoocs, in consequence of its gills being destitute of bony rays; by which it is peculiarly distinguished from all the preceding orders, and obtains a mark which has been laid hold of by Linnaeus as constituting its ordinal character. It consists, for the most part, of a group of sea-monsters, or natural deformities, if the term might be allowed; as the ostraceon or trunk-fish, the diodon and tretradon, sun-fish, and lump-fish, many of which are so completely truncated at either end as to resemble the middle part of any common large fish with its head and tail lopped off; the syngnathus, pipe or needle-fish; and the lophius or frog-fish. In one of the species of this last kind we meet with a singular decoy for entrapping smaller fishes as its prey. This species, 1. piscatorius, which is about seven feet long, and inhabits most European seas, lurks behind sand-hills or heaps of stone, and throwing over them the slender appendages on his head, which have the appearance of worms, entices the smaller fishes to advance and play around them till they come within his reach, when he instantly darts forward and secures them as his spoil.

The Sixth and last Order Of Fishes is denominated Chondroptervgious, as having the gills wholly cartilaginous, which constitutes its ordinal character. It includes, among other kinds, the acipenser or sturgeon, squalus or shark, raia or ray, petromyzon or lamprey, and gastrobranchus or hag-fish. Of these, one of the most useful is the sturgeon: its different species may be ranked among the large fishes; they are inhabitants of the sea, but ascend rivers annually. The flesh of all of them is most delicious; from the roe is procured the sauce called caviare, and from the sounds and muscular part is made isinglass. They feed on worms and other fishes, and the females are larger than the males.

This order, in the shark, contains the most dreadful of all the monsters of the main. The squalus Carcharias or white shark, which often extends to thirty feet in length, and four thousand pounds in weight, follows ships with a view of devouring every thing that comes in his way, and has occasionally been known to swallow a man whole at a mouthful. But in order to guard us in some degree against the perils of their presence, a peculiar stream of light issues in the dark from their tapering, subcompressed bodies, which cannot well be mistaken; and as some compensation for their rapacity, we obtain from their liver a large quantity of useful oil, and find in their skin a very valuable material for carriage-traces in some countries, and for polishing wood, ivory, and other hard substances, in all countries.

The next class to that of fishes in an ascending direction is named Amphibia; which, for the sake of brevity, and having no English synonym to meet it, I shall take leave now, as I have on former occasions, to render Amphibials. The term, indeed, whether regarded as Greek or English, is not very strictly precise in its present application; for it intimates an intention to include in this class all animals capable of existing in the two elements of air and water. We have already observed, however, that there are various fishes, as the eel-tribe generally, one species of the perch, and two or three of the exocoetus or flying-fish, to which many more might be added, that are capable of existing in air as well as in water; while the insect kinds offer us a still greater number that are similarly endowed, and the worms a still more numerous train. It has been said, indeed, that the animals of this class have a peculiar agreement in the structure of their organs of respiration, which

« AnteriorContinuar »