CHAPTER XVIII.

FISHES.

Before speaking of the habits of the principal kinds of fishes, it is desirable to glance at their organization, and upon the manner in which they execute their physiological functions.

Fishes are intended to live always[14] in water, and this circumstance has impressed its seal upon their organization. Nevertheless, their forms are very varied; they are generally oblong, compressed laterally. They have no neck, the head being merely a prolongation of the trunk. In the majority of instances, the body is covered with scales, generally a thin bony substance developed out of the skin and overlapping each other, like the tiles of a roof.

Nothing is more remarkable than the variety and brilliancy of colour in fishes; they present almost every gradation, from golden or silver, and other dazzling colours, mingling with shades of blue, green, red, and black.

Fishes are essentially formed for swimming (Fig. 340), and all their members are adapted for this purpose. The anterior members, which correspond with the arms in man and the wings in birds, are attached to each side of the trunk, immediately behind the head, and form the _pectoral fins_. The posterior members occupy the lower surface of the body, and form the _ventral fins_. The latter, which are always over the ventral line, may be before, beneath, or behind the former. Fishes possess, besides, fins in odd numbers. The fins which erect themselves on the back are called the back or _dorsal fins_, those at the end of the tail are the _caudal fins_; finally, there is frequently another attached to the lower extremity of the body, which is called the _anal fin_. These fins are always nearly of the same structure, consisting generally of a fold of the skin, supported by slender, flexible, cartilaginous or osseous rays, connected by a thin membrane.

The muscles which bind together the vertebral column are so much developed in fishes as well as others of the superior animals, that they constitute in them alone the principal part of the body. The caudal, dorsal, and anal fins act as outlying oars; the pectoral and ventral fins assist in progression, at the same time that they help to maintain the equilibrium of the animal and guide and direct its movements, which are generally astonishing from their rapidity.

An organ, which belongs properly to fishes[15] (Fig. 341), and which is usually considered as their chief aid in swimming, is a large bladder situated within the body, between the dorsal spine and the abdomen. This is usually called the _swimming bladder_. According to the volume this bladder assumes, the animal can increase or diminish the specific gravity of its body; that is, it can remain in equilibrium or ascend or descend in the bosom of the waters; it is, moreover, remarked that it is very small in those species which swim at the bottom of the water, and Mr. Gosse says there is some reason for considering it to be the first rudimentary form of the air-breathing lung.

Immediately behind the head, two large openings are observed in most fishes; these are the gill-openings. Their anterior edge is mobile, and they are raised or lowered to serve the purposes of respiration; under this species of covercle are the gills, or branchiæ. These usually consist of many rows of thin membranous plates, hung on slender arches of bone, placed on each side of the head, usually protected by a bony plate made up of several pieces, called the _gill-covers_. The breathing is produced by water taken in at the mouth, which passes over the gill-membranes, and is ejected through an orifice at the hind margin of the gill-covers. During the contact of the water with the gills, the blood which circulates in these organs, and which communicates to them the red colour by which we recognize them, combines chemically with the oxygen of the air which the water holds in solution when it flows freely at the ordinary temperature in presence of the air. The blood is thus oxygenized, or made fit for respiration.

The heart in fishes is placed between the inferior parts of the branchial arch, and consists of a ventricle and an auricle (Fig. 342). It corresponds with the right half of the heart in the Mammifera and birds, for it receives the venous blood from all parts of the body and sends it to the gills. From this organ the blood is delivered into one great artery, which creeps along the vertebral column.

The eye in fishes is generally very large--we may even say enormous relative to the size of the head--and without true eyelids; the skin usually passes over the ocular globe, and becomes from this point so transparent that the luminary rays traverse it. This light covering is all the eyelid belonging to fishes. The interior of the eye is covered by the membrane called _choroid_, the thin external leaf of which, in consequence of the presence of innumerable microscopic crystals, presents the appearance of a gold or silver-coloured coating, which gives to the iris that extraordinary brilliancy which belongs to the fish's eye. The crystalline lens is voluminous, spherical, and diaphanous. When the fish is cooked, the crystalline lens constitutes that opaque and hard white substance which often comes under the teeth in eating fish of a certain size. Cuvier suspected, what anglers now know to be true, that those active chasseurs of the deep saw far and very clearly.[16]

If fishes have great eyes, they have, on the other hand, very small ears. This organ, it is found, has no exterior opening. It forms a cavity in the interior of the cranium, which is far from presenting the complicated structure of the ear in mammifers and birds. In spite, however, of the imperfect structure, fishes are sensible to the least noise. In consequence, silence is a rigorous law with the fisherman.

The dimensions of the mouth and teeth are very variable in fishes; these organs are in proportion to their voracity, which in many of these beings is very great. The form and development of the buccal pieces are also very various. Some species are toothless, but in most fishes the teeth are very numerous. They are sometimes attached, not alone to the two jaws, but also to the palate, to the tongue, and upon the interior of the branchial arch, and even in the back mouth, that is to say, upon the ospharyngeal, which surrounds the mouth of the oesophagus.

The form of their teeth is very variable both in arrangement and position: some are in the form of an elongated cone, either straight or curved. When small and numerous, they are comparable to the points of the cards used in carding wool or cotton. Sometimes they are so slender and dense as to resemble the piles of velvet, and often, from their very minute size, their presence is more easily ascertained by the finger than the eye. In some members of the Salmonidæ, for instance, we find a row of teeth on the bone that forms the middle ridge of the palate, which is called the _vornex_. On each side of this is another row on the _palatine_ bones, and outside these is a third pair of rows on the upper jaw-bones. Some fishes have flat teeth, with a cutting edge in front of the jaws, like a true incisor; others have them rounded or oval, adapted to bruise or crush the various substances on which they feed.

The oesophagus connected with the mouth is short in fishes; the stomach and intestines vary in form and dimensions. Digestion is very rapid with these beings. Most of them feed on flesh, but there are a few where the mouth is without teeth, which feed on vegetables.

The growth of fishes is slow or very rapid, according to the abundance of food; they can suffer a very long fast, but in that state they become diminutive in size, and finally perish of exhaustion. At certain seasons an irresistible impulse brings the two sexes together. Many species whose ordinary appearance is dull and unsightly now shine in the most brilliant colours. The female soon after lays her eggs, the number of which passes all imagination. Nature seems to have accumulated in the body of each female myriads of eggs--a wise provision, which is rendered necessary by the numerous causes of destruction which threaten them in their native element. The eggs, abandoned by the females to the mercy of the waves, are fecundated after being deposited by the milt of the males. Such is a very brief summary of the organization of fishes, which have been briefly described as vertebrate, cold-blooded animals, breathing by means of gills; living in water, moving through the water by means of their fins, and reproducing their kind by means of eggs, or spawn. And now a few words on their classification.

Fishes naturally divide themselves into two series, according to the composition of their internal skeleton. This is usually osseous; nevertheless, a whole group of them constantly retain the cartilaginous or fibro-cartilaginous state. With some this frame presents even less power of resistance, and remains membranous.

It is precisely upon this peculiarity of structure that we found the great division of the class of fishes into two great groups of CARTILAGINOUS and OSSEOUS fishes, the first being again subdivided into three orders: namely, I. _Cyclostomata_, II. _Selachia_, III. _Sturiona_. The second into four orders: I. _Plectognathii_, II. _Lophobranchii_, III. _Malacopterygii_, IV. _Acanthopterygii_. Agassiz's system of classification of fish, founded on the form of the scales, is perhaps better suited than this to the palæontologist, but the one given above, founded as it is principally on the internal parts of the animal, is better suited to the zoologist. Agassiz's orders are the _Ctenoid_, type, _Chromis_, _Placoid_, _Ganoid_, and _Cycloid_.

CARTILAGINOUS FISHES.

Cartilaginous fishes are generally animals of considerable size, their structure ranging from ordinary fishes to eels. They are chiefly sea-fishes, only a few species being river-fishes. Naturalists divide them into two orders; namely, those having the gills free on the outer edge (the gilled _Chondropterygeans_), and those having these organs fixed on both edges. The first order comprehend three families: I. _Cyclostomata_, or Eels, Lampreys, &c., in which the mouth forms a sucker; II. _Selachians_, including Raias and Sharks, in which the mouth is furnished with jaws; III. _Sturiona_, or Sturgeons, which have the gills free.

I. CYCLOSTOMATA.

The first are characterised by the singular conformation of the mouth, which is formed for suction. The body is elongated, naked, and viscous, reminding us of serpents in their external form; they have neither pectoral nor ventral fins; their vertebræ are reduced to simple cartilaginous rings, scarcely perceptible one from the other, traversed by tendons, and covered by a second and more solid series of rings, which surround the soft cartilaginous spine. Their gills, in place of presenting the comb-like appearance of other fishes, have something of the form of a purse. The lampreys may be considered as the type of this family.

The Lampreys (_Petromyzon_) are cylindrical, with seven gill-openings on each side of the neck, forming two longitudinal lines; mouth round, armed with many teeth. The Sea Lamprey, _P. marinus_ (Fig. 348), belongs to the Mediterranean; it is also found in the German Ocean, and the friend who supplies this note has caught it with cockle bait in the South Esk, Forfarshire. In the spring it ascends the rivers, where it is sometimes caught in abundance. Full-grown it is about three feet long, marbled brown upon yellow; the dorsal fins are separated by long intervals; its mouth is circular and surrounded by a fleshy lip, furnished with cirri, having a cartilaginous plate for support; it is provided on its internal surface with many circular rows of strong teeth, some single, the others double.

The Lamprey feeds on worms, molluscs, and small fishes; its mouth is a powerful sucker, by the aid of which it attaches itself to fishes often of great size, and sucks them like a leech. It is taken by hook and line, and speared by a sort of barbed harpoon, like the trident of the mythological Neptune, which is thrown, javelin fashion, at the animal when seen at the bottom of the water; the flesh is fat and delicate. In the twelfth century one of our kings, Henry I., surfeited himself at Elbeuf by partaking too largely of the Lamprey. The river-lamprey resembles the above in its general conformation, but is much smaller, and differs in the armature of the mouth, having only a single circular row of teeth. It is blackish above, silvery beneath, and is common in the markets of London and Paris, being frequently taken in the Seine. A smaller species, about ten inches in length, never leaves the fresh waters. It resembles the last species in colour, but its two dorsal fins are continuous; it is found in most European rivers and brooks. In some of the English rivers they are frequently taken in the eel-pots, weighing two and three pounds. They frequent stony bottoms, where they find small animals on which they feed. In its larva state it was long considered to be a distinct species of _Ammocætes_; it is now, however, ascertained that it only acquires its perfect form at the end of its second or third year.

II. SELACHIA.

The Selachians include a great number of cartilaginous fishes, varying much in form, including the rays, dog-fish, skate, torpedo, hammer-fish, sharks, and saw-fish; they have pectoral and ventral fins. On each side of the neck, on the lower surface, are five gill-openings, in form of a slit to each gill. Many of the species have two _blow-holes_ in the upper part of the head. The order is divided into Raiadæ and Squalidæ.

RAIADÆ.

Of the RAIADÆ there are several genera, and many species. In _Cephaloptera_ the head is truncated, with large, lateral eyes. In _Myliobates_ it is projecting, the pectoral fins extending like wings. In _Trygon_ it is enclosed by the pectorals. In the Skate (_Raia_) the body is rhomboidal, tail without spine, but two small dorsals near the top. In the _Torpedo_ the body is nearly round, the tail short and fleshy, with two dorsals and a caudal fin.

The White Ray, _Raia batis_ (Fig. 349), reminds us of the lozenge shape, the point of the muzzle forming the lower angle, the longest ray of each pectoral forming the lateral angles, while the summit of the tail forms the last angle; the whole surface seems flat, but a swelling is distinguishable towards the head, on the upper surface, which bears, as it were, the contour of the body, properly so called, namely, the three cavities of the head, the throat, and the belly, which occupy the centre of the lozenge, beyond which the pectoral fins extend. These fins, though covered with a thick skin, permit the cartilaginous rays, with their articulations, to be very distinctly seen.

The head of the white ray, which terminates in a muzzle slightly pointed, is attached behind to the cavity of the breast. The mouth, placed in the lower part of the head and far from the extremity of the muzzle, is elongated; its edges are cartilaginous, and furnished with many rows of hooked and pointed teeth; the nostrils are placed in front of the mouth. The eyes, which open in the upper part of the head, are half projecting, and protected in part by a continuation of the soft, elastic, and retractile skin which covers the head. Immediately behind the eyes are two blow-holes, which communicate with the interior of the mouth. The animal is able to open and close these holes at pleasure, by means of an extensible membrane, which acts as a sort of valve. Through these holes it ejects the superabundant water beyond what is necessary for respiration. In its general colour the animal is ashy grey on its upper surface; white, with rows of black spots, below.

Its tail is long, flexible, and slender, acting at once as a rudder and a weapon of offence or defence. When lying in ambush, nearly buried in mud at the bottom of the sea, and it has no desire to change its position, a rapid and sudden stroke of this formidable weapon, armed with hooked bones on its upper surface, arrests its victim by wounding or killing it, without disturbing the mud or seaweed by which it is covered. This species sometimes attains a very considerable size, and their flesh is firm and nourishing; but the larger specimens rarely approach inhabited shores, even when the female desires to lay her eggs. These eggs have a very singular shape, differing from almost every other fish, and particularly from those of all other osseous fishes. They are quadrangular, a little flat, each of the four corners terminating in a small cylindrical beak--a kind of pocket formed of a strong and transparent membrane.

The Lump-fish, _R. clavata_ (Fig. 350), so called in consequence of its armature, inhabits every European sea; sometimes it attains the length of twelve feet, and, being excellent eating, is much sought after by fishermen. It is frequently seen with the skate in European markets. A ray of great curving spines occupies the back and extends to the end of the tail; two similar spines are above, and two below the point of the muzzle. Two others are placed before, and three behind the eyes. Each side of the tail is furnished with a row of shorter spines; the whole surface, in short, bristles with larger or smaller spines, justifying the name of buckler-fish; for these are not given by way of ornament, but defence. The colour of the upper surface is generally brown, with whitish spots. The tail, which exceeds the body in length, presents towards the end two small dorsals, terminating in a caudal fin.

Ray-fish of all kinds are inhabitants of the deep sea, but they change according to the seasons. While stormy weather prevails, they hide themselves in the depth of the ocean, where they lie in ambush, creeping along the bottom. But they do not always live at the bottom. They rise occasionally to the surface far from the shore, eagerly chasing other inhabitants of the deep, lashing the water with their formidable tails and fins, springing out of the water, and making it foam again under their gambols.

When pursuing their prey the rays employ their great pectoral fins, which resemble wings, and are aided by a very delicate and mobile tail; they beat the waters in order to fall unexpectedly upon their prey, as the eagle swoops down upon its victim. It may thus be called the king of fishes, as the eagle is the king of birds.

The Cramp-fish, _Torpedo marmorata_ (Fig. 351), has considerable analogy with the Raia. Its flattened body forms a roundish disk, beyond which its rays form large pectoral fins; but the humeral girdle which carries them, carries also, in a great hollow, a most singular organic apparatus, which possesses the property of producing violent electrical commotions. This apparatus is placed in the interval between the end of the muzzle and the extremity of the fin, and completes the rounded disk of the body. The mouth is small, the slit crosswise; the jaws bare; the teeth in squares of five. The eyes are small; behind them are two star-like spout-holes. On the lower surface of the breast are two rows of small transverse slits, openings of the gill pouches, like those of the rays. The tail is thick, short, and conical, carrying part of the ventral, and terminating in a sort of caudal fin. On the back are two small, soft, and adipose fins. The skin is smooth; its colour varies with the species; generally it is reddish-brown, with eye-like spots of a deep blue in the centre; sometimes azure, and surrounded by a great brownish circle; the spots being five or six. These curious fishes are found in the Channel and on the shores of the Mediterranean.

The electrical effects produced on the fisherman who seizes them were noted from early times; but Redi, the Italian naturalist of the seventeenth century, was the first who studied them scientifically. Having caught and landed one of them with every precaution, "I had scarcely touched and pressed it with my hand," says the Italian naturalist, "than I experienced a tingling sensation, which extended to my arms and shoulders, which was followed by a disagreeable trembling, with a painful and acute sensation in the elbow joint, which made me withdraw my arm immediately."

Réaumur also made some observations upon the Torpedo. "The benumbing influence," he says, "is very different from any similar sensation. All over the arm there is a commotion which it is impossible to describe, but which, so far as comparison can be made, resembles the sensation produced by striking the tender part of the elbow against a hard substance." Redi remarks, besides, that the pain and trembling sensation resulting from the touch diminishes as the death of the Torpedo approaches, and that it ceases altogether when the animal dies.

In the seventeenth century, the fishermen affirmed that the sensation was even communicated through the line by which it was caught, and even by the water. Redi does not deny this phenomenon, neither does he confirm it. He states that the action of the animal is never more energetic than when it is strongly pressed by the hand, and makes violent efforts to escape. Neither Redi nor Réaumur, however, could explain the cause of the strange phenomenon. It was reserved for Dr. Walsh, a fellow of the Royal Society of London, to demonstrate the fact that the power was electrical in its nature. This he did by numerous experiments, which he made in the Isle of Ré. The following are some of his experiments.

He placed a living torpedo upon a clean wet towel; from a plate he suspended two pieces of brass wire by means of silken cord, which served to isolate them. Round the torpedo were eight persons, standing on isolating substances. One end of the brass wire was supported by the wet towel, the other end being placed in a basin full of water. The first person had a finger of one hand in this basin, and a finger of the other in a second basin, also full of water. The second person placed a finger of one hand in this second basin, and a finger of the other hand in a third basin. The third person did the same, and so on, until a complete chain was established between the eight persons and nine basins. Into the ninth basin the end of the second brass wire was plunged, while Dr. Walsh applied the other end to the back of the torpedo, thus establishing a complete conducting circle. At the moment when the experimenter touched the torpedo, the eight actors in the experiment felt a sudden shock, similar in all respects to that communicated by the shock of a Leyden jar, only less intense.

When the torpedo was placed on an isolated supporter, it communicated to many persons similarly placed from forty to fifty shocks in a minute and a half. Each effort made by the animal, in order to give them, was accompanied by the depression of its eyes, which were slightly projecting in their natural state, and seemed to be drawn within their orbits, while the other parts of the body remained immovable.

If only one of the two organs of the torpedo is touched it happens that, in place of a strong and sudden shock, only a slight sensation is experienced--a numbness, or start, rather than a shock. The same result followed with every experiment tried. The animal was tried with a non-conducting rod, and no shock followed; glass, or a rod covered with wax, produced no effect; touched with a metallic wire, a violent shock followed. Melloni, Matteucci, Becquerel, and Breschet have all made the same experiments with the same results--Matteucci having ascertained that the shock produced by the torpedo is comparable to that given by a voltaic pile of a hundred to a hundred and fifty pairs of plates.

The organ which produces this curious result is formed like a half-moon; it is double, and placed on each side of the mouth of the respiratory organs. It consists of a multitude of small prisms arranged parallel the one to the other and perpendicularly to the surface; twelve hundred and sixty-two of these prisms have been counted in one of the two organs of a torpedo, three feet in length. Without entering into the anatomical descriptions which have been given by Stannius, Max Schultze, Breschet, and others, we may mention here that all the small parallelopipedes, which enter into their structure, are separated one from the other by walls of cellular tissue, in which are distributed the vessels and nerves. The nervous threads which each apparatus receives are divided into four principal trunks. According to modern authors, the electricity is elaborated in the brain under the influence of the will. It is afterwards transferred by means of the nervous threads into the principal organ, where it serves the purpose of charging the numerous little voltaic piles which constitute the organ of commotion.

It is, nevertheless, necessary to receive our comparisons of the apparatus of the torpedo with the voltaic pile of our laboratories with caution. The apparatus resembles a good conducting body, which is capable of being strongly electrified; it is sufficient to touch one of the surfaces in order to receive the shock. But if the little prisms composing it were charged like our voltaic piles, it would be necessary to touch both their surfaces in order to receive the shock. No perfect analogy can therefore exist between this natural apparatus and the scientific instrument named after Volta.

It is possible by the aid of heat to restore the extinct or suspended electrical functions of the torpedo. Retained in a tank of sea-water a yard in height by a third of that in diameter, and at 22° Centigrade in temperature, a torpedo preserved its faculties during five or six hours; another, which remained during ten hours in a very small quantity of sea-water at a temperature of 10° to 11° Cent., and which seemed dead, revived a little when placed in water at 20° Cent., and gave shocks during an hour. If held firmly by the tail, and pressed both above and below by a platinum rod to gather the true electricity, the animal contracts itself violently; but its movements are not always accompanied by electrical discharges, which demonstrate that the jets of electrical matter are not the result simply of the muscular contractions, but that they are subject to the will of the animal, and evidently given for resisting its enemies, and benumbing its prey. How wonderful and varied are the resources which Nature grants to her creatures in order to secure their existence!

SQUALIDÆ.

This family approaches more to the Raias than any other fish; but all the species have a lengthened body, merging into a thick tail, pectorals moderate in size, gill-openings on the sides of the neck, and not beneath the body, as in the Raia; eyes lateral; and the roughness of their skin is a protection from their enemies. The family comprehends the _Sharks_, _Dog fishes_, _Hammerheads_, and _Saw fish_.

The sharks are said to attain the length of twenty and even thirty feet; but its size is not its worst attribute. It has received, besides, strength and terrible arms. Ferocious, voracious, impetuous, and insatiable, spread over almost every climate, an inhabitant of every sea, and recently not seldom seen on our own shores, the shark rapidly pursues every fish, which fly at its approach; and threatens with its wide gullet the unfortunate victims of shipwreck, shutting them out from all hope of safety.

The body of the shark is long, and its skin is studded with small tubercles: this skin becomes so hard, and takes so high a polish, that it is employed for various ornamental purposes. This resisting power protects the shark from the bites of every inhabitant of the sea, if there be any daring enough to approach it with that view.

The back and sides of the Shark, _Carcharius vulgaris_ (Fig. 352), are of an ashy brown; beneath it is faded white. The head is flat, and terminates in a muzzle slightly rounded. Its terrible mouth is in the form of a semicircle, and of enormous size; the contour of the upper jaw of a shark of ten yards length being about two yards wide, and its throat being of a proportionate diameter to this monstrous opening. When the throat of the animal is open we see beyond the lips, which are straight and of the consistence of leather, certain plates of teeth, which are triangular, dentate, and white as ivory. If the shark is an adult it has in the upper as in the lower jaw six rows of these murderous arms, an arsenal ready to tear and rend its victim. These teeth take different motions according to the will of the animal, and obedient to the muscles round their base, by means of which it can erect or retract its various rows of teeth; it can even erect a portion of any row, while the others remain at rest in their bed. Thus this far-seeing tyrant of the ocean knows how to measure the number and power of the arms necessary to destroy its prey: for the destruction of the weak and defenceless one row of teeth suffices; for the more formidable adversary it has a whole arsenal at command.

The eyes of the shark are small, and nearly round; the iris of a deep green, the eyeball, shaped in a transversal slit, is bluish; its scent is very subtle; its fins are strong and rough.

The pectoral fins are triangular, and much larger than the others, extending on each side, and giving powerful aid in swimming. The caudal fin is divided into two very unequal lobes, the upper extending in a sloping direction to twice the length of the other. This tail is possessed of immense power, and is capable of breaking the limb of a robust man by a single stroke.

During the hot season the male and female seek each other; they approach the coast roving in company, forgetting their ferocity for the time. The eggs are hatched at several periods in the ovary, from which the little ones issue two or three at a time.

The shark, as soon as born, becomes the scourge of the sea. He seizes all that come near him. He eats the cuttle-fish, molluscs, and fishes; among others, flounders and cod-fish. But the prey which has the greatest charm for him is man; the shark loves him dearly, but it is with the affection of the gourmand. It even manifests, according to some authors, a preference for certain races. If we may believe some travellers, when several varieties of human food comes in its way, the shark prefers the European to the Asiatic, and both to the negro. Still, whatever may be the colour, he seeks eagerly for human flesh, and haunts the neighbourhood where it hopes to find the precious morsel. He follows the ship in which his instinct tells him it is to be found, and makes extraordinary efforts to reach it. He has been known to leap into a boat in order to seize the frightened fishermen; he throws himself upon the ship, cleaving the waves at full speed, to snap up some unhappy sailor who has shown himself beyond the bulwarks. He follows the course of the slaver, watching for the horrors of the middle passage, ready to engulf the negroes' corpses as they are thrown into the sea. Commerson relates a significant fact bearing on the subject. The corpse of a negro had been suspended from a yard-arm twenty feet above the level of the sea. A shark was seen to make many efforts to reach the body, and it finally succeeded in seizing it, member by member, undisturbed by the cries of the horror-stricken crew assembled on deck to witness the strange spectacle. In order that an animal so large and heavy should be able to throw itself to this height, the muscles of the tail and posterior parts of the body must have an astonishing power.

The mouth of the shark being placed in the lower part of the head, it becomes necessary to turn itself round in the water before it can seize the object which is placed above him. He meets with men bold enough to profit by this conformation, and chase this formidable and ferocious creature. On the African coast the negroes attack the shark in his own element, swimming towards him, and seizing the moment when he turns himself to rip up his belly with a sharp knife. This act of courage and audacity cannot, however, be said to be shark-fishing. The fishing operation is conducted as follows:--Choosing a dark night, a hook is prepared by burying it in a piece of lard, and attaching it to a long and solid wire chain; the shark looks askance at this prey, feels it, then leaves it; he is tempted by withdrawing the bait, when he follows, and swallows it gluttonously. He now tries to sink into the water, but, checked by the chain, he struggles and fights. By-and-by he gets exhausted, and the chain is drawn up in such a manner as to raise the head out of the water. Another cord is now thrown out with a running knot or loop, in which the body of the shark is caught about the origin of the tail. Thus bound, the captured shark is soon hoisted on deck, as represented in PL. XXV. On the quarter-deck of the ship he is put to death, not without great precaution, however, for he is still a formidable foe, from his terrible bites and from the still dangerous blows of his tail. Moreover, he dies hard, and long resists the most formidable wounds.

Captain Basil Hall gives a spirited sketch of the appearance and capture of one of those dreaded fishes; a capture in which the whole ship's company, captain, officers, young gentlemen inclusive, shout in triumphant exultation as the body of the shark flounders in impotent rage on poop or forecastle.

"The sharp-curved dorsal fin of a huge shark was seen rising about six inches above the water, and cutting the glazed surface of the sea by as fine a line as if a sickle had been drawn along it: 'Messenger, run to the cook for a piece of pork,' cried the captain, taking the command with as much glee as if an enemy's cruiser had been in sight. 'Where's your hook, quartermaster?' 'Here, sir, here,' cried the fellow, feeling the point, and declaring it was as sharp as any lady's needle, and in the next instant piercing with it a huge junk of pork weighing four or five pounds. The hook, which is as large as one's little finger, has a curvature about as large as a man's hand when half closed, and is six or eight inches in length, while a formidable line, furnished with three or four feet of chain attached to the end of the mizen topsail halyard, is now cast into the ship's wake.

"Sometimes the very instant the bait is cast over the stern the shark flies at it with such eagerness that he actually springs partially out of the water. This, however, is rare. On these occasions he gorges the bait, the hook, and a foot or two of the chain, without any mastication, and darts off with the treacherous prize with such prodigious velocity that it makes the rope crack again as soon as the coil is drawn out. Much dexterity is required in the hand which holds the line at this moment. A bungler is apt to be too precipitate, and jerk away the hook before it has got far enough into the shark's maw. The secret of the sport is to let the monster gulp down the whole bait, and then to give the line a violent pull, by which the barbed point buries itself in the coat of the stomach. When the hook is first fixed, it spins out like the log line of a ship going twelve knots.

"The suddenness of the jerk with which the poor devil is brought up often turns him quite over. No sailor, however, thinks of hauling a shark on board merely by the rope fastened to the hook. To prevent the line breaking, the hook snapping, or the jaw being torn away, a running bowline is adopted. This noose is slipped down the rope and passed over the monster's head, and is made to join at the point of junction of the tail with the body; and now the first part of the fun is held to be completed. The vanquished enemy is easily drawn up over the taffrail, and flung on deck, to the delight of the crew."

The flesh of the shark is leathery, of bad taste, and difficult to digest. Nevertheless, the negroes of Guinea feed upon it, but not until it has been made tender and eatable by long preservation. In many parts of the Mediterranean coast small sharks are taken from their mother's belly and eaten. The under part of adult sharks is also eaten by the fishermen after the bad parts have been removed. In Norway and Iceland this part of the animal is dried in the air during the most part of the twelve months. The Icelanders also use the fat of the animal; the liver of one of them, according to Pontoppidan, will furnish a great quantity of oil.

We have thus, with the care it deserves, painted the portrait of the shark. The original is by no means beautiful; but, frightful as it may be, our description would be incomplete if we did not add that divine honours have been granted to this monster of the waters. Man worships force; he knows the hand which crushes, the teeth which rend. He respects the master or the king who strikes, and he venerates the shark. The inhabitants of several parts of the African coast worship the shark; they call it their _joujou_, and consider its stomach the road to heaven. Three or four times in the year they celebrate the festival of the shark, which is done in this wise.

They all move in their boats to the middle of the river, where they invoke, with the strangest ceremonies, the protection of the great shark. They offer to him poultry and goats, in order to satisfy his sacred appetite. But this is nothing; an infant is every year sacrificed to the monster, which has been reared for the purpose from its birth; it is fêted and nourished for the sacrifice from its birth to the age of ten. On the day of the fête it is bound to a post on a sandy point at low water; as the tide rises, the child may utter cries of horror, but it is abandoned to the waves, and the sharks arrive. The mother is not far off; perhaps she weeps, but she dries her tears and thinks that her child has entered heaven through this horrible gate.

The Dog-fish, _Acanthias vulgaris_ (Fig. 353), which sometimes attains the length of between three and four feet, is exceedingly voracious. It feeds upon other fish, of which it destroys great quantities; it does not hesitate to attack the fishermen, and especially bathers in the sea. It places itself in ambush, like the Raias, in order to attack its prey. The flesh of the dog-fish is hard, smells of musk, and is rarely eaten; but the skin becomes an article of commerce, and is known as _shagrin_, being, like the skin of the shark, used for making spectacle-cases and for other ornamental purposes, for which its green colour and high polish recommend it. There is a smaller species than the preceding, which haunts rocky shores, where it lies in wait for its prey. Its spots are larger and more scattered, and its ventral fins are nearly square. It feeds on molluscs, crustaceans, and small fishes.

The Hammerhead, _Zygæna malleus_ (Fig. 354), is chiefly distinguished by the singular conformation of its head, which is flattened horizontally, truncate in front, and the sides prolonged transversely, giving it the appearance of the head of a hammer. The eyes of this fish are placed at the extremity of the lateral prolongations of the head; they are grey, projecting, and the iris is gold-coloured. When the animal is irritated, the colours of the iris become like flame, to the horror of the fishermen who behold them.

Beneath the head and near to the junction of the trunk is the mouth, which is semicircular, and furnished on each jaw with three or four rows of large teeth, pointed and barbed on two sides.

The most common species in our seas is long and slender in the body, which is grey, the head blackish. It usually attains the length of eleven or twelve feet, weighing occasionally nearly five hundred pounds. Its boldness and voracity, and craving for blood, are more remarkable than its size. If the hammerhead has not the strength of the shark, it surpasses it in fury; few fishes are better known to sailors in consequence of its striking conformation. Its voracity often brings it round ships even in roadsteads, and near the coast. Its visits impress themselves on the memory of the sailor, and he loves to relate his hairbreadth escape from the meeting.

The saw-fish is distinguished from all other known fishes by the formidable arm which it carries in its head. This weapon is a prolongation of the muzzle, which, in place of being rounded off or reduced to a point, forms a long, strong, straight, sword-like termination, flat on both sides, but on the two edges it is furnished with numerous strong teeth of considerable length, which are prolongations of the hard, bony substance which forms the muzzle--forming, in short, a sword-blade deeply toothed on each edge.

Thus armed, the saw, or sword-fish, as it is sometimes called, the length of which is from twelve to fifteen feet, fearlessly attacks the most formidable inhabitants of the sea. With its threatening weapon, sometimes two yards in length, it dares to measure its strength with the whale. All fishermen who visit the northern seas assert that the meeting of these ocean potentates is always followed by a combat of the most singular kind, in which the activity of the sword-fish is a match for the formidable strength of the whale. Occasionally it dashes itself with such force against the sides of a ship, that its sword is broken in the timber. In the British Museum the blade of a sword-fish may be seen which was thus implanted in the timber of a ship.

III. STURIONA.

In the second division of cartilaginous fishes, or sturgeons, the gills are free, as in the ordinary fishes. In the sturgeon the gill-openings are a single, very wide orifice, with an operculum, but without radiating membrane. They are fishes of great size, living in the sea, but ascending the larger rivers in the spawning season. Our space only permits us to notice the Chimæra and Sturgeon.

The naturalists Clusius and Aldrovandus compared the fish, to which they gave the name of _Chimæra arctica_, to the chimæra, a monster of mythological antiquity, which is represented with the body of a goat, the head of a lion, the tail of a dragon, and a gaping throat which vomited flames. The strange form of this fish, the manner in which it moves, the different parts of its muzzle, its mode of showing its teeth, its ape-like contortions and grimaces, its long tail, which acts with such rapidity,--reminding one not a little of a reptile,--are well calculated to strike the imagination. At a later period mediæval naturalists were contented to see in it a fish with a lion's head, and as the lion was then regarded as the king of animals, so the chimæra became the _Herring_ king.

The king of the herrings (Fig. 355) is from five to six feet in length, of a general silvery colour, spotted with brown. It inhabits the North Sea, living on molluscs and crustaceans; occasionally, as if to justify the title which has been given it, levying heavy contributions upon the herrings. Another species, _C. antarctica_, is found in the southern hemisphere, which greatly resembles, in its conformation and habits, the northern species. In both the end of the muzzle terminates in a cartilaginous appendage, which projects forward, curving afterwards over the mouth. This extension assimilates to a crest.

The sturgeons (_Acipenser_) are among the largest fishes known. On this account, as well as from their exterior conformation, they approach the _Squalidæ_. Their muscles, however, are less firmly knit, their flesh more delicate, and their muscular strength consequently infinitely smaller. Neither is their mouth armed with so many rows of teeth. Moreover, they are less voracious, and their habits are not at all ferocious.

The sturgeons are sea-fishes which periodically ascend the larger rivers. Several species are known in Europe. They abound in the Black Sea and Sea of Azof, but they are chiefly known as frequenting the Volga and the Danube. The enormous consumption of caviare in Russia leads to a deadly pursuit of the common sturgeon in all the great European rivers, and this species is in a fair way of disappearing altogether.

The Common Sturgeon, _Acipenser sturio_ (Fig. 356), abounds in the North Sea and the Mediterranean, and occasionally it appears in the Thames, the Rhine, the Seine, the Loire, and the Gironde. It is usually about two yards to seven feet long, but has been known to attain the length of ten or twelve feet. Its general colour is yellow, with a white belly. It is rendered remarkable by the number and form of the osseous plates or scales, which cover the body like so many bucklers. Upon the back and belly are no less than twelve to fifteen of these rough bony plates, relieved by projections, which are pointed in the young, and soften down with age. On each side is a row of thirty to thirty-five of these triangular plates, separated from each other by considerable intervals. The head is broad at the base, gradually contracting towards the point, and terminating in a conical muzzle. The mouth is large and considerably behind the extremity of the muzzle, and its jaws, in place of teeth, are furnished with cartilages. Between the mouth and the muzzle are four slender and very elastic barbs, or wattles, like so many little worms. It is pretended that these wattles attract small fishes to the jaws of the animal, while it conceals itself among the roots of aquatic plants.

In the sea the sturgeon feeds on herrings, mackerel, cod-fish, and other fishes of moderate size. In the rivers it attacks the salmon which ascend them about the same time. Mingling with them, however, it seems a giant. It deposits its eggs in great quantity, which are gathered and made into caviare. Its flesh is delicate, and in countries where they are caught in quantities it is dried and preserved. The rivers which enter the Black and Caspian seas contain, besides the common sturgeon, many other species of the same genus, the flesh of which is even more delicate and _recherché_ than the common sturgeon. Among the ancients this fish was held in unusual esteem. In Rome, in the time of the emperors, we read of sturgeons borne in triumph to the sound of instruments, and laid upon tables fastidiously covered and decorated with flowers.

The Great Sturgeon, which sometimes exceeds a thousand pounds, is only found in the rivers which flow into the Caspian and Black seas. The Volga, the Don, and the Danube produce the largest species.

We are indebted to the Russian naturalist Pallas for the information we possess respecting the mode of taking the sturgeon in the Volga and other Asiatic rivers. Stakes are placed across the river, leaving just sufficient space between each pile to permit the animal to pass. Towards the centre this dike forms an angle opposed to the current, and, consequently, opposed to the fish which ascend the river towards the summit of this angle. At this point there is an opening which leads into a kind of enclosure, consisting of fillets towards the end of winter, and of osier-hurdles during summer. The fishermen establish themselves upon a sort of scaffold placed over the opening. When the fish is engaged in the reservoir, the men upon the scaffold drop a gate, which prevents his return to the sea. The movable bottom of the chamber is now raised, and the fishes easily taken, as represented in PL. XXVI.

The fishermen are informed during the day of the approach of the sturgeons to the great enclosure by the movement they communicate to cords suspended to small floating substances in the water. During the night the sturgeons enter the enclosure, agitating by their movements other cords arranged round the hurdles. The agitation communicated to the cord is sufficient to shut the gates behind; they are thus imprisoned by the dropping of the gate, which in falling sounds a bell to wake the watching fisherman on the scaffold, should he be asleep. The sturgeon-fisheries of the Volga are thus admirably organized. Gmelin describes with some minuteness the sturgeon-fishing, during the winter, in the caverns and hollows of the river-banks near Astrakhan, in the estuary of the Volga. A great number of fishermen are assembled there with their boats. The flotilla approaches the retreats to which the fishes have betaken themselves, the nets are skilfully arranged all round them, and all at once the whole mass of fishermen join in a great cry, at which the frightened fishes rush from their concealment and throw themselves into the nets spread for them.

The size of the fish, the nourishing properties of its flesh, its healthy and agreeable taste, and the immense quantity of eggs produced, have a wonderful power in exciting the commerce and industry of the inhabitants of these countries. In order to give some idea of the abundance of the eggs of the sturgeon, it is stated that the weight of two ovaries equalled nearly a third of the weight of the whole animal; in other words, these ovaries weighed nearly eight hundred pounds in a female whose weight was two thousand eight hundred pounds.

It is with these eggs chiefly, but not altogether, that caviare is prepared; and the article is more or less relished according to the state of the eggs. The display of caviare, as exhibited at the Universal Exposition of Paris during the year 1867, will remain to those who have visited it one of the most lasting recollections.

FOOTNOTES:

[Footnote 14: The exceptions to these are the Doras, or flat-headed Hassar of India, which marches overland in large droves; the Swampines of Carolina (_Hydrargyra_); and the Perca Scandens, which in Tranquebar not merely walks over level ground, but climbs trees.]

[Footnote 15: Some fish, as the _Chondropterygii_, have no swimming bladder.--ED.]

[Footnote 16: Dr. Fripp's theory of the properties of the fish's eye is very plausible.

1st. That the fish's eye in its normal state is arranged for the vision of near objects, and that the great refractive power of a prolate spheroid lens, such as exists in the fish, is adequate to the production of a picture at short focal distances, even with rays of light passing through so dense a medium as water.

2nd. That there is no accommodation of the fish's eye for extended limits of vision.

3rd. That the passive state of the fish's eye, being that in which it is enabled to see objects near and at moderate distance, no active or physiological change for accommodation of sight for distant objects takes place or seems necessary.

The dioptric arrangement, being the reverse of that which obtains in animals where "accommodation" is observed, and in whom the _passive state_ is that of vision, arranged for distant objects, while the _active state_ is that of vision accommodated at will for near objects.

4th. That the vascular distribution of the choroid vessels has no relation to any movement of the lens or change of its shape, but is arranged to meet the changes of static condition of the circulating fluid, and of dynamic force exerted by the heart under varying pressure from without; and that by such an arrangement, protection to the delicate tissues of the eye is afforded by a compensating balance between the tension of the blood within the vessels and the external pressure exerted upon them.]