The fins, the chief instruments of motion, consist of a certain number of elastic rays of processes, either of one single piece, in the form of a spine, or of jointed pieces. The strong or spiny rays are placed at the fore part of the fin, and the soft or jointed rays towards the back part. By the various flexures of these organs, the movements of fishes are conducted; the perpendicular fins, situated on the back or upper part of the animal, keeping the body in equilibrio, while the tail operates as a rudder at the stern of a vessel, and the side or breast-fins as oars. The stomach is large, the intestines far shorter than in quadrupeds and birds: and the liver is very large, usually placed on the left side.

The air-bladder, or swimming bladder, is a very highly curious and important organ, lying closely beneath the backbone, and provided with a very strong muscular coat, which gives it the power of contracting at the pleasure of the fish, so as to condense the air, with which it is filled, and thus enable the animal to descend to any depth, and again to ascend by being restored to its largest size. Some fishes are destitute of the air-bladder, yet remain always at the bottom; as the whole tribe of flat-fish. The teeth are, in some tribes, large and strong, in others, very small,; in some, sharp; in others obtuse; in some, numerous; and in others, few. Sometimes they are placed in the jaws; sometimes in the palate or tongue; or, even at the entrance of the stomach. The eyes are, in general, large, flattened, or less convex than in quadrupeds and birds. In return, the central part of the eye, or what is called the crystalline humour, is of a globular shape, to give the animal the necessary power of vision, and to compensate for the comparative flatnes of the cornea.

The organ of smelling, in fishes, is large; and they have the power of contracting or dilating it at pleasure. This sense is extremely acute. The organ of hearing differs, in some particulars, from that in other animals, and is modified according to the nature of the fish. They are entirely destitute of voice. The particular kind of sound or chirp, which some tribes are observed to make, on being first taken out of the water, is entirely owing to the sudden expulsion of air from their internal cavities. The greater number of fishes arc oviparous, producing soft eggs, usually known by the name of spawn. There have been 200,000 ova or eggs found in a carp; in a perch, weighing one pound two ounces, 69,216; in a carp of eighteen inches, 342, 144; in a sturgeon of one hundred and sixty pounds, there was the enormous number of 1,467,500!!! The age of fish is determinable by the number of concentric circles of the vertebræ or joints of the back-bone. In the Linnæan arrangement of fishes, the

under or belly-fins, are termed ventral, and are considered analogous to the feet in quadrupeds; and it is from the presence or absence of the fins, that the divisions are instituted. Far as creation's ample range extends,

The scale of sensual, mental powers, ascends:
Mark, how it mounts to man's imperial race,
From the green myriads in the peopled grass:
What modes of sight betwixt each wide extreme
The mole's dim curtain, and the lynx's beam:
Of smell, the headlong lioness between,
And hound sagacious, on the tainted green:
Of hearing, from the life that fills the flood,
To that which warbles thro' the vernal wood!
The spider's touch, how exquisitively fine!
Feels at each thread, and lives along the line:
In the nice bee, what sense so subtly true!
From poisonous herbs extracts the healing dew:
How instinct varies in the groveling swine,
Compar'd, half-reasoning elephant, with thine!
"Twixt that, and Reason, what a nice barrier!
For ever separate,-yet for ever near!

177. The fishes are divided into six orders, namely; 1. Apodes: 2. Jujulares: 3. Thoracici: 4. Abdominales: 5. Branchiostegi: 6. Chondropterygii.

I. Apodal fish have bony gills; and no ventral fins, as the eel.

II. Jugular fish have bony gills; and the ventral fins situated directly under the pectoral fins, as the cod, haddock, and whiting.

III. Thoracic fish have bony gills; and the ventral fins situated directly under the pectoral fins, as the perch and mackerel.

IV. Abdominal fish have bony gills; and the ventral fins on the belly behind the pectoral fins, as the salmon, herrings, and carp.

V. Branchiostegeous fish have their gills destitute of bony rays, as the sucker.

VI. Chrondropterygeous fish have cartilaginous fins as the sturgeons, sharks, and skate.

SECTION III.

THE INSECT CLASS.

178. Insects are distinguished from other animals by their being furnished with never fewer than six feet; and sometimes with many more; by their breathing, by spiricles or breathing-holes, situated at certain distances along each side of the body; and lastly, by the head being furnished with a pair of antennæ, or jointed horns, which are extremely various in the different tribes.

The first state in which the generality of insects appear, is that of an egg. From this is hatched the animal in its second state, when it is improperly called the caterpillar. The insect, in this state, is the larva or larve, a mask or disguise of the animal in its future form. The larve differs in its appearance, according to the tribe to which it belongs. When the time arrives for the larve to change into its next state of chrysalis, or pupa, it ceases to feed, and having placed itself in some quiet situation, for the purpose, lies still for several hours; and then by a laborious effort, frequently repeated, divests itself of its external skin, or larve-coat, and immediately appears in the very different form of a pupa. The Linnæan term pupa was given, from the indistinct resemblance which many insects bear in this state to a doll, or a child when swathed up, according to the old fashion. The pupa cmerges at length the complete insect, in its perfect or ultimate form, from which it never can after change, nor can it receive any further increase of growth. This last or perfect state is termed the imago.

Thick, in yon stream of light, a thousand ways,
Upward, and downward, thwarting, and convolv'd,
The quivering nations sport; till, tempest-wing'd,
Fierce Winter sweeps them from the face of day;
E'en so, luxurious man, unheeding pass
An idle summer-life in fortune's shines
A season's glitter! Thus they flutter on
From toy to toy, from vanity to vice:-

Till blown away by death, oblivion comes

Behind, and strikes them from the Book of Life.

THOMSON.

179. Some insects undergo a change of shape, but are hatched complete, in all their parts from the egg, and only cast

;

their skin from time to time, during their growth, till they acquire the full size of their species. The mouth in some tribes is formed for gnawing the food, and operates by a pair of strong horny jaws, moving laterally as in the beetle tribe while in others, it is formed for suction, and consists of a sort of tube. In the butterfly, and moth tribe, it consists of a double tube, which, when at rest, is rolled into a spiral form, and when in use, extended at full length. The eyes differ in the different tribes, the greater number of insects are furnished with eyes apparently two in number, and situated on each side the head. The outward surface of the coats of these eyes may be compared to so many convex lenses or glasses. The head of the common dragon-fly, is furnished with 25,000 of these lenses! In spiders, the eyes are from six to eight in number; of a simple structure, and placed at a considerable distance from each other.

Observe the insect-race-ordain'd to keep
The lazy sabbath of a half-year's sleep!
Entomb'd beneath the filmy web they lie,
And wait the influence of a kinder sky;
When vernal sun-beams pierce their dark retreat,
The heaving tomb distends with vital heat-
The full-form'd brood impatient of their cell,
Start from their trance, and burst their silken shell!
Trembling awhile they stand, and scarcely dare
To launch at once upon the untry'd air-
At length assur'd they catch the fav'ring gale,
And leave their sordid spoils, and high in ether sail !
Lo! the bright train, their radiant wings unfold
With silver fring'd, and freckled o'er with gold;
On the gay bosom of some fragrant flow'r
They idly fluttering live their little hour,
Their life all pleasure, and their task all play,
All spring their age, and sunshine all their day!
Not so the Child of Sorrow-Wretched Man-
His course with toils concludes with pain began
That high his destiny he might discern
And in Misfortune's school this lesson learn-
Pleasure's the portion of the inferior kind,
But Glory-Virtue-Heaven for Man design'd!

BARBAULD.

180. The muscles, or organs constituting the several portions of the flesh in insects, are more numerous than in the larger animals, and extremely irritable. In the human body, the muscles scarcely exceed 500, in a large caterpillar more than 4000 have been discovered! The power of the muscles is also much greater than in animals. A flea is capable of

springing at least 200 times its own length; whereas the jerbo and kangaroo in their most powerful springs, fall very short of the same proportional distance.

Wak'd by his warmer ray, the reptile young
Come wing'd abroad; by the light air upborne,
Lighter, and full of soul. From every chink,
And secret corner, where they slept away
The wintry storms; or rising from their tombs,
To higher life; by myriads, forth at once,
Swarming, they pour; of all the varied hues,
Their beauty-beaming parent can disclose.

Ten thousand forms, ten thousand different tribes
People the blaze! To sunny waters some,
By fatal instinct fly; where on the pool,

They, sportive, wheel; or sailing down the stream,
Are snatch'd immediate by the quick-ey'd trout
Or darting salmon. Through the green-wood glade
Some love to stray; there lodg'd, amus'd, and fed,
In the fresh leaf. Luxurious, others make
The meads their choice, and visit every flower,
And every latent herb; for the sweet task,
To propagate their kinds, and where to wrap,
In what soft beds, their young, yet undisclos'd,
Employs their tender care. Some, to the house,
The fold, and dairy, hungry, bend their flight;
Sip round the pail, or taste the curdling cheese.
Oft, inadvertent, from the milky stream
They meet their fate; or, weltering in the bowl,
With powerless wings, around them wrapt, expire.

THOMSON.

181. The orders of insects are, 1. Coleoptera: 2. Hemiptera: 3. Lepidoptera: 4. Neuroptera: 5. Hymenoptera: 6. Diptera: 7. Aptera.

I. Coleopterous insects have elytra or crustaceous cases covering the wings; and which, when closed form a longitu dinal division along the middle of the back, as in the chaffer.

II. Hemipterous insects have four wings, the upper ones partly crustaceous, and partly membranaceous; not divided straight down the middle of the back, but crossed, or incumbent on each other, as in the cock-roach.

III. Lepidopterous insects have four wings covered with fine scales almost like powder, as in the butterflies and moths. IV. Neuropterous insects have four membranous and semi-transparent wings veined like net-work; and the tail without a sting, as in the dragon-fly and ephemera.