Natural History, Fishes/Cartilaginei
ORDER IV. CARTILAGINEI.
(Cartilaginous Fishes.)
The largest and most formidable of all fishes are found in this Order. “The peculiar structure of their skeleton, which gives rise to their name, admits of these animals continuing to grow as long as they live; the consequence of which is, that as they inhabit the wide ocean, and have few enemies, they are sometimes met with of such an enormous size that their weight and dimensions are almost incredible.”[1]
The great essential character of the Order is the nature of their skeleton. Their bones have but a very small quantity of earthy matter in their composition; and what is present is deposited in grains, and not in distinct fibres. The skull is not divided into separate bones, but is formed in a single piece; yet ridges, furrows, and holes on its surfaces, enable the anatomist to discover the portions, which in other fishes are distinct, though here soldered, as it were, together. Even bones, that in other fishes constitute moveable joints, are not always distinct in this Order; the vertebræ or joints of the spine, for example, are, in some of the Rays, united into a single mass; and in other genera, some of the bones of the face are quite wanting. The bones of the jaws, known to anatomists under the names of maxillaries and intermaxillaries, are reduced, throughout the Order, to mere rudiments concealed beneath the skin: and the functions proper to them are performed by other bones of the mouth, as the palatals and the vomer.
Most persons who have ever looked at the backbone of any ordinary fish that is brought to table,—a Mackerel, a Cod, or a Salmon,—are aware that each vertebra is hollowed into a funnel-shaped cavity on each face, which is filled with a gelatinous substance: and that the centre is pierced with a slender hole, through which this jelly passes, thus forming a continuous cord, dilated and contracted alternately, throughout the spine. In many species of this Order the gelatinous cord varies very little in its diameter; and in some, the central tube of communication is so much enlarged as to reduce the solid part to a mere ring of cartilage.
It is observable that this Order presents us with some fishes having peculiarities of organization of a higher type than is found elsewhere in the whole Class, exhibiting a close affinity with the Reptiles; and even making a distinct approach to the Cetaceous Mammalia. "The viviparous Sharks," says the learned author of Horæ Entomologicæ, "such as the Basking-Shark (Selache maxima, Cuv.), with their ear more perfectly organized than that of other fishes, and their body destitute of scales, the particular disposition of their fins, and their closed branchiæ, all indicate at what place we are to enter among the fishes upon leaving the Cetaceous quadrupeds."[2]
On the other hand, the scale of organization descends to a lower point in the Cartilaginous than any reached in the Osseous Orders. In the extreme forms the skeleton becomes obsolete; the spine is no longer divided into vertebræ, but is reduced to a soft, flexible, transparent, and slender column or thread of cartilage; and the animals can only with the utmost difficulty be distinguished from Worms.
Thus it seems probable that in a truly natural arrangement, as the illustrious Cuvier has suggested, the Cartilaginei ought not to be placed either above or below other Fishes, but rather as forming a parallel series, or Sub-Class, as the Marsupialia form a series of Mammalia, parallel with the Placentalia.
The Cartilaginous Fishes are not very numerous, when compared with the other Orders: they are, however, widely scattered, some of them being found in all seas, from the equator to the seas surrounding either pole. They are almost exclusively marine; the Sturgeons and the Lampreys, however, are exceptions, inhabiting rivers. Five Families are included in this Order, named, respectively, Acipenseridæ, Chimæradæ, Squalidæ, Raiadæ, and Petromyzonidæ.
Family I. Acipenseridæ.
(Sturgeons.)
The Sturgeons have their gills free, like other fishes, with a single opening, which is comparatively wide, and protected by a large, oval, radiated plate, as a gill-cover; there are no gill-rays. The gill-plate, being furnished with a membranous margin, can close the aperture so accurately as to exclude water, and even air. The body is long, and tapering gradually to the tail, which is furnished with a caudal fin of remarkable structure. It is unequally forked, the upper lobe being considerably the longer; but this is not the only difference, for (as in the Shark, which exhibits the same form of the caudal,) the upper lobe is penetrated by the terminal joints of the spinal column, which run through its centre to the extremity; the lower lobe is formed only of rays. The body and the head are covered with large bony plates, those on the head of various angular forms, fitting into each other, those on the body arranged in longitudinal rows, with their centres rising into spines pointing backwards. The mouth, situated beneath the head, is small and toothless; it is placed on a sort of foot of three joints, by means of which it is capable of considerable protrusion.
These are fishes of large size, some, indeed, attaining gigantic dimensions; they inhabit rivers, lakes, and inland seas, and chiefly in the northern regions of the globe. They migrate at certain seasons to the sea, but deposit their spawn in freshwater. Twenty-four species are enumerated by the Prince of Canino as belonging to the Family, including one or two singular species of North America, which, with most of the characters above-mentioned, have the snout prolonged into a broad, leaf-like, bony plate.
Genus Acipenser. (Linn.)
In addition to the characters already detailed, the Sturgeons have the snout more or less prolonged and pointed, and furnished, on its under surface, with several cirri or beards, which hang down in front of the tubular, protrusile mouth. The fins are rather small, and, with the exception of the pectorals, are all placed far behind. The flesh in general is wholesome and agreeable; the roe, which is of considerable bulk, is made into a substance called caviare, held in high estimation in some parts of Europe; isinglass of the best quality, is made of the inner coats of the large and thickened air-bladder; and the skin is sometimes made into leather, or prepared as a substitute for window-glass. Hence these fishes are the subjects of important fisheries, especially in the east of Europe. The Russian fisheries, on the Caspian Sea, are very valuable; three species inhabit that great inland lake,—the Common Sturgeon (Acipenser sturio), the Great Sturgeon (A. huso), and the Sevruga (A. helops). The number of fishes taken in a single season is immense; of the first species named, three hundred thousand; of the second, one hundred and three thousand; of the third, one million three hundred thousand; are considered as the annual average. The products of isinglass, and caviare, exclusive of the flesh, which is preserved in various ways, and is a valuable article of merchandise, are alone worth more than 100,000l. per annum.
We have said that these fishes attain large dimensions; the Common Sturgeon, which occasionally ascends the rivers of this country, has been taken of the weight of four hundred and sixty pounds; and the Great Sturgeon attains a length of twenty feet, and a weight of two thousand pounds; of which the roe, which constitutes its chief value, weighs one fourth part.
The Sturgeon, when taken in the Thames, is called a Royal fish, by which is meant, that it ought to be, and formerly was, presented to the sovereign, for the royal table. The flesh, which is much more solid than that of fish generally, is considered as a great delicacy; it is usually stewed with a rich gravy, and is commonly compared to veal. It was held in high repute among the luxurious Romans, in the times of the empire: according to Pliny it was brought to table with much pomp, adorned with garlands; the slaves who carried the dishes were also decorated in a similar manner, and marched to the sound of music.
Caviare is prepared in the following way. The roes, taken out and placed in tubs, are cleansed with water; the fibrous parts, by which the ova are connected, are removed, and the spawn is rinsed in white wine, or vinegar, and spread to dry. It is then put into a vessel and salted, being crushed down at the same time with the hands, and afterwards inclosed in linen bags to drain off the moisture. Finally, it is packed in tubs, pierced in the bottom, that any remaining moisture may yet drain off, and closed down for domestic use or exportation. Sometimes it is said to be preserved, after having been salted and seasoned, by being rolled up into large balls, and immersed in vessels of oil; or the rolls are inclosed in wax, so that the air may be more effectually excluded.
To make isinglass, the air-bladders are washed carefully in water, and the outer membrane is removed; what remains is then rolled up in a cloth, and kneaded with the hands, until it has become thoroughly softened. Each bladder is then moulded into a cylindrical form, dried in a gentle heat, and bleached with the fumes of brimstone.
The Common Sturgeon has the snout slender and pointed; the body is somewhat five-sided, being studded with five rows of bony plates, that run down the whole length; one along the back, another along each side, and two more bordering the belly. These plates are oval, with a curved spine in the centre of each. The ground colour of the body is brown on the upper parts, and silvery-white beneath; the plates are bone-white.
Family II. Chimæradæ.
(Chimeras.)
The name Chimæra, that of a monstrous compound being in classic fable, was applied by Linnæus to a cartilaginous fish, on account of its singular and uncouth appearance. One species alone was known to him, a native of the northern seas, but a second, if not a third, has since been added from the southern hemisphere.
The Chimæradæ have much resemblance to the Sharks in external appearance; having the same general form, and nearly the same arrangement of the fins. In the peculiarities of their respiratory organs, they hold an intermediate place between these fishes and the Sturgeons, for while there is only one external gill-aperture on each side, yet the gills are not properly free, but adhere by portions of their edges, so as to leave five openings communicating with the external aperture. Their jaws are merely rudimentary; hard undivided plates supply the place of teeth, four above and two below.
Genus Chimæra. (Linn.)
The body is lengthened, terminating in a slender filament; there are two dorsals, the first short, high, and preceded by a stout spine; the second low and very long. The males are distinguished by three pointed bony appendages to the ventrals, and by a very singular hoe-like horn on the snout, bent forwards and tipped with spines. In the Northern Chimæra (Chimæra monstrosa, Linn.) the head is strangely uncouth, the snout ascending in a blunt point; the mouth far below, small; the face and cheeks scored with
irregular waved furrows. The colours are beautiful; many shades of rich brown, on a shining white ground; the eyes are particularly large and brilliant. It attains three feet in length, and is sometimes seen on the northern coasts of Scotland. From its pursuit of the shoals of Herrings, on which it principally feeds, it is sometimes called the King of the Herrings. The female deposits large leathery eggs or capsules, flattened, with velvety margins, having some resemblance to those of Sharks or Rays. These eggs are esteemed by the Norwegians, who eat them in pastry; the flesh of the animal is coarse, hard, and uneatable. An oil is extracted in copious quantity from the liver, to which medicinal properties are attributed.
Family III. Squalidæ.
(Sharks.)
We now come to a Family which contains the most highly organized members, not only of their Order, but of the whole Class of Fishes. They are generally of large size, sometimes gigantic; are carnivorous and voracious; and some of them are universally dreaded for their ferocity, their appetite for human flesh, their strength, and the formidable array of teeth with which their mouth is furnished. The White Shark (Carcharias vulgaris), that terror of the tropical seas, has been repeatedly known to cut a man’s body in twain at a single snap; and accounts are current of human bodies having been found entire in the bodies of these terrible monsters. Nor will this seem incredible when we consider that this species is sometimes found twenty feet in length.
This and the following Family agree in having the gills attached at their outer margin, with a separate orifice to each, through which the water escapes. These orifices are commonly five in number. In the Sharks the body is lengthened, and of the usual fish-form, that is, tapering from behind the head to the tail, with but little swelling in the middle; the muzzle is more or less pointed, and projects, so that the mouth opens beneath; the nostrils also are situated beneath the snout. All the fins are distinct and free; there are usually two dorsals, two large pectorals, two ventrals with (in the males) two large appendages at their inner edge, an anal, and a caudal of two unequal lobes, as before described in the Sturgeons. The body and fins are covered with a hard leathery skin, almost always rough
to the touch if the hand be passed from the tail upwards. This roughness arises from the presence of small angular spiculæ of crystalline appearance, imbedded in the skin, and fits the skin and fins of various species to be used for polishing cabinet-work. In some species the skin is studded with curved spines.
The teeth of the Sharks constitute a most formidable apparatus. They are generally triangular, very sharp-pointed, and often have a small point on each side the principal one; they are flat, and the edges are keenly cutting, so that they resemble lancets; moreover, in some cases, the edges themselves are notched into minute saw-like teeth. Each of these lancet-teeth alone, in a Shark of considerable size, would inflict a severe gash; what then must be the effect of a whole mouthful of such weapons, above and below, arranged in serried order, rank behind rank, and moved with the force of powerful muscles? The teeth of a fossil Shark are found two inches and a half in diameter, from base to point.
The mode by which the race of these formidable creatures is continued, differing as it does so greatly from that of most other fishes, is exceedingly curious. The Shark, instead of depositing some millions of eggs in a season, like the Cod or the Herring, produces two eggs, of a square or oblong form, the coat of which is composed of a tough horny substance; each corner is prolonged into a tendril, of which the two which are next the tail of the enclosed fish are stronger and more prehensile than the other pair. The use of these tendrils appears to be their entanglement among the stalks of sea-weeds, and the consequent mooring of the egg in a situation of protection and comparative security. Near the head there is a slit in the egg-skin, through which the water enters for respiration, and another at the opposite extremity by which it is discharged. That part of the skin which is near the head, is weaker and more easily ruptured than any other part; a provision for the easy exclusion of the animal, which takes place before the entire absorption of the vitellus or yolk of the egg, the remainder being attached to the body of the young fish, enclosed in a capsule, which for a while it carries about. The position of the animal, while within the egg, is with the head doubled back towards the tail, one very unfavourable for the process of breathing by internal gills, and hence there is an interesting provision made to meet the emergency. On each side a filament of the substance of the gills projects from the gill-opening, containing vessels in which the blood is exposed to the action of the water. These processes are gradually absorbed after the fish is excluded, until which the internal gills are scarcely capable of respiration. How curious an analogy we here discover with the Frogs and Newts among the Reptiles; and how impressively do we learn the Divine benevolence, when we find that the object of so much contrivance and care is the dreaded and hated Shark!
In some species the horny capsules in which the young are enclosed at birth are destitute of the filamentous prolongations of the angles; in some they have but two projecting points, one end being rounded; while other species, as the Penny Dog (Galeus vulgaris), and Smooth Hound, (Mustelus lævis), of our own shores, bring forth their young alive and fully formed, without any capsule or covering at all.
A hundred and fourteen species are reckoned by Prince Bonaparte to belong to this Family; some or other of which are scattered over all seas. Fifteen are enumerated among British Fishes, either as habitual residents in our waters, or as accidental stragglers. Considerable difficulty is felt by naturalists in the attempt to subdivide the family into natural groups; not from the number of the species so much as from the diversities of form and structure that exist among them. The following is the arrangement proposed by Mr. Swainson.
1. Zygænina. The Hammer-heads. These have an obvious and well-marked character in the form of the head, which is enormously dilated, so that the eyes appear placed at the ends of long projections. (See figure of Zygæna laticeps, an Indian species, on page 15.) These fishes attain a large size, and are said to be ferocious and formidable; one is occasionally taken on our coasts.
2. Pristina. The Saw-fishes. These are Sharks with many characters of the Rays; distinguished by the snout being prolonged into a straight flat bony blade, along the edges of which are set pointed teeth, directed outwards. This well-armed sword is a formidable weapon, which it is said the ferocious Saw-fish frequently buries in the flesh of the Whale and other marine animals. The preceding engraving represents the singular forms of these two Sub-families.
3. Squalina. The True Sharks. These have the ordinary form, the nose being somewhat pointed, the body slightly swelling behind the head. There are two dorsals, which have no
spines before them; and there are no air-holes (spiracles) behind the eyes. To this group, which far exceeds any of the others in the number of its component species, belong the giants of the race, the Basking Shark (Selachus maximus), thirty-six feet in length, the Blue Shark (Carcharias glaucus), the Fox Shark (C. vulpes), and the dreaded White Shark (C. vulgaris).
Many thrilling anecdotes of the fatal voracity of this last named monster of the deep are on record. One of these is recorded by a painting in Christ's Hospital, London. The late Sir Brooke Watson was swimming at a little distance from a ship, when he saw a Shark making towards him. Struck with terror at its approach, he cried out for assistance. A rope was immediately thrown to him; but even while the men were in the act of drawing him up the ship's side, the ferocious creature darted after him, and at a single snap, tore off his leg.
The horrors inflicted on the miserable sufferers by the shameful traffic in men, during the transit across the Atlantic, are heightened by these ferocious animals. Their instinct apprises them of the probability of prey; the air, tainted with the effluvia of a multitude of human beings crowded together in a tropical climate, probably awakening their vigilance and whetting their appetite. It is affirmed that numbers of Sharks almost invariably attend every slave-ship throughout her voyage, crowding around her stern, awaiting with eager expectation the unceremonious committal to the deep of the numerous wretches who fall victims to suffocation, disease, or despair.
"Here dwells the direful Shark. Lured by the scent
Of steaming crowds, of rank disease, and death,
Behold! he rushing cuts the briny flood,
Swift as the gale can bear the ship along;
And, from the partners of that cruel trade
Which spoils unhappy Guinea of her sons,
Demands his share of prey, demands themselves."
A dreadful instance of the voracity of these formidable animals occurred a few years ago among the Society Islands. Upwards of thirty natives were passing from one island to another, in a large double canoe, which consists of two canoes fastened together, side by side, by strong horizontal beams, lashed to the gunwales by cordage. Being overtaken by a storm, the canoes were torn apart, and were incapable, singly, of floating upright. In vain the crew attempted to balance them, they were every moment overturned. Their only resource was to form a hasty raft of such loose boards and spars as were in the craft, on which they hoped to drift ashore. But it happened, from the small size of their raft, and their aggregated weight, that they were so deep in the water, that the waves washed above their knees. Tossed about thus, they soon became exhausted with hunger and fatigue; when the Sharks began to collect around them, and soon had the boldness to seize one and another from the raft, who being destitute of any weapon of defence, became an easy prey. The number and audacity of these monsters every moment increased, and the forlorn wretches were one by one torn off, until, but two or three remaining, the raft at length, lightened of its load, rose to the surface, and placed the survivors beyond the reach of their terrible assailants. The tide at length bore them to one of the islands, a melancholy remnant, to tell the sad fate of their companions.
Of the immense numbers of these fishes that exist in the tropical seas, some idea may be formed from the fact that in a single harbour (that of Kingston), on the coast of Jamaica, from one hundred to one hundred and fifty thousand are destroyed annually. These are principally young ones, which are taken in numbers at every haul of the seine. On our own coast Sharks (not, however, of this species) are very numerous. Mr. Couch says of the Picked Dog-fish (Spinax acanthias), "I have heard of twenty thousand taken in a seine at one time." These also were young ones. But they have doubtless many enemies; and few of the young which swarm in such incredible numbers, live to attain adult age and dimensions.
4. Spinacina. The Dog-fishes. These are readily recognised by the spiracles or air-holes which are placed, one on each temple, just behind the eye. The dorsals in several of the genera are each preceded by a strong spine. This also is a numerous group, and includes most of the British Sharks.
5. Squatinina. The Angel-fishes. This is the form by which the Sharks merge into the Family of the Rays. It is much depressed, with the head broad, flat, and rounded; the eyes are placed on the summit of the head, and the mouth at the extremity, while the gill-apertures are beneath. The pectorals are enormous, as are the ventrals, giving to the fish that rhomboidal outline common to the Skates: the dorsals also are placed far back. This subdivision is represented by a British species, Squatina angelorum, of large size and great voracity, and held in no esteem.
Genus Scyllium. (Cuv.)
In this genus, belonging to the fourth of the above Sub-families, we find spiracles on the temples distinct, though small. There is an anal fin, as well as two dorsals; the first dorsal placed opposite or behind the ventrals, the second behind the anal: the head is short, and the muzzle rounded; the nostrils, pierced near the mouth, are continued by a fissure in the upper lip, forming valves. The teeth are small and acute, with a small point on each side of the principal lobe. The caudal is lengthened, oblique, irregularly lobed, and truncate (or apparently cut short) at the tip.
The names of Dog, Hound, Beagle, and such like, commonly applied to the common Sharks of this and other similar genera, are believed to have reference to their habit of following their prey in packs. They may have allusion also to the prevalent style of colouring in these fishes; spots of varying size, of black, brown, or liver-colour profusely scattered over a light ground, often clouded with brown and yellow.
Like the rest of the Family the Dog-fishes are ground feeders; a habit indicated by the position of the mouth beneath the projecting snout. This habit is not at variance with the fact that several species, such as the Basking, the White, and the Blue Sharks, frequent the warm surface of the sea, at certain seasons, as this has reference to other requirements in their economy.
We have two British species of this genus, of which the Large-spotted Dog, or Bounce (Scyllium catulus, Linn.), here represented, is the handsomer and the larger. It attains a length of three feet; is of a brownish grey hue on the upper parts, and whitish beneath; the whole elegantly studded with large round spots of black, or deep brown.
The Dog-fishes are excessively voracious, and, in the pursuit of prey, seem at times quite fearless of man. They follow vessels with eagerness, seizing everything eatable that is thrown overboard; they have even been known to dart at fishermen, and at persons bathing in the sea; though their comparatively small mouths, and their weakness, prevent their ability to inflict serious mischief in this way. They are, however, hated by the fishermen on account of the depredations they commit on more valuable fishes than themselves, great quantities of which they devour, when taken in the nets. The Dog-fish itself is often captured both by the net, and by the hook; but is perfectly valueless when caught; except for the trivial use that is made of the skin in polishing.
“On the coasts about Scarborough, where the Haddocks, Cod, and Dog-fish, are in great dance, the fishermen universally believe that the Dog-fish make a line or semicircle, to encompass a shoal of Haddocks and Cod, confining them within certain limits near the shore, and eating them as occasion requires. Haddocks and Cod are always found near the shore, without any Dog-fish among them; and the Dog-fish are found farther off, without any Haddocks or Cod; and yet the former are known to prey upon the latter; and, in some years, they devour such immense numbers as to render this fishery more expensive than profitable."[3]
Family IV. Raiadæ.
(Rays.)
In the flattened form of the Saw-fish (Pristis), and in the great enlargement of the pectorals in the Angel (Squatina), we saw distinct approaches made by the Family of the Sharks to that of the Rays. In these the pectorals are enormously dilated, their bases, which are continuous with the body, extending from the base of the tail to the head, and sometimes stretching out in front of the head in the form of lobes. Hence the ordinary shape of these fishes is more or less rhomboidal, or square, the snout forming one corner, and the tail projecting from the opposite, the other two corners being the angles of the pectoral fins. The body is broad, but thin and flat; and a common skin invests both it and the fins: the ventrals are commonly large, and in the males are furnished with appendages resembling those of the Sharks: the dorsals are two, sometimes three in number, small, and placed very far back upon the slender tail; sometimes, indeed, close to its extremity; a minute caudal is occasionally seen, but more frequently wanting; the dorsals also are, in some species, obliterated.
The eyes, and the temporal spiracles, are placed on the upper surface: the latter are much larger than in the Sharks, often exceeding the size of the eyes; they communicate internally with the mouth and gills. The mouth, the nostrils, and the gill-openings are placed on the under-surface, and quite concealed from view in the ordinary position of the fish as it flounders along on the bottom of the sea. The gill-openings agree with those of the Sharks in number, form, and structure. The mouth is small, and set with numerous teeth, which are arranged in close array like paving-stones; they are more or less square, and flat; but in old males, the middle ones assume a pointed form, overlapping one another, and pointing backward towards the throat.
As in many of the Sharks, the eyes are furnished with a nictitating membrane, or skin, which can be drawn over the eye-ball at pleasure, serving the purpose of an eyelid.
The young of the Rays are enveloped at birth, like those of some of the Sharks, in capsules of thin horn or leathery substance. They are generally more square in form, with the angles produced, but not attenuated to long filaments. The accompanying figure represents the egg-capsule of the Common Skate, frequently found on our sea-beaches, and commonly called Skate-purses. In the north of England, they are called Skate-barrows, from their obvious resemblance in form to a hand-barrow. As the inclosed young grows, the angular projections of the pectoral fins bend over upon the body, and thus room is afforded for the little creature to attain that
size and maturity which are requisite for it, when it forces its way out at an elastic crevice, to procure its living in freedom.
The Rays, like the Pleuronectidæ or Flat-fishes of the Osseous Orders, to which they possess many curious analogies, are strictly ground-feeders. They habitually grovel along on the soft muddy bottom, moving with a peculiar undulating action of the pectorals. The great size, however, of these fins indicates that, on occasion, they can shoot along with great swiftness. They are very voracious, devouring any fishes that they can master, as well as crustacea, and shelled mollusca; the strong flat teeth, with which their jaws are paved, are able to crush to powder the stoutest shells of lobsters and crabs. Some of the species, especially those of tropical seas, grow to an immense size, and are ferocious in proportion to their dimensions. Specimens of the Cephaloptera have been seen twenty five feet in length, and thirty in breadth; and one was captured a few years ago at Barbadoes, which weighed three thousand five hundred pounds. Col. Hamilton Smith saw one of these monsters seize and carry down a man who was swimming in the sea near Trinidad.
About a hundred and thirty species are known to belong to this Family, all of which are marine. They are found in all seas, and the British coasts possess no fewer than sixteen. The following groups constitute the Sub-families of the Rays.
1. Rhinobatina. The Shark-rays. This form may be considered as almost equally partaking of the characters of the two Families whose names it conjointly bears. The body is much longer than broad, the tail is thick, and tapers gradually from the trunk; the snout is short and elongated. They mostly inhabit the Indian Ocean and the Red Sea.
2. Torpedinina. The Electric Rays. Here the tail is short and fleshy, but distinctly separated from the disk of the body, which is nearly circular. The space between the pectorals and the head and gills, is occupied on each side by an apparatus capable of giving electric shocks of considerable force, though not equal in power to those of the Gymnotus. The organs consist of a number of cells exactly resembling the hexagonal cells of a honey-comb, subdivided by lateral membranes, and containing a transparent jelly-like fluid. In the magnificent physiological Museum of the Royal College of Surgeons, there are several beautiful representations, most exquisitely modelled, of these organs in connexion with the surrounding parts. Two species of these fishes are found on the British coast, often called Cramp-fish, and Numb-fish, from the effect produced on the nerves of any one who comes into contact with them.
The object of so singular a power is but imperfectly conjectured. The fish is voracious and carnivorous, and this endowment may enable it to disarm and subdue its prey, which otherwise might be too strong or too active to be over-powered. But Mr. Couch suggests another object, with high probability. He says;—"One well-known effect of the electric shock is to deprive animals killed by it of their organic irritability, and consequently to render them more readily disposed to pass into a state of decomposition,[4] in which condition the digestive powers more speedily and effectually act upon them. If any creature more than others might seem to require such a preparation of its food, it is the Cramp-Ray, the whole canal of whose intestine is not more than half as long as the stomach."
3. Raiana. The Skates. The rhomboidal or lozenge-shaped outline, is eminently characteristic of this group, which is the most numerous of the whole. The tail is moderately long and slender; furnished with two small dorsals, and generally terminated by a small caudal. The skin on the upper parts, particularly of the tail, is generally studded with asperities, tubercles, or curved prickles, but never armed with a long, serrated bony spine. Eleven of our British species belong to this group.
4. Trygonina. The Sting-rays. In these the head is surrounded and inclosed by the pectoral fins; the disk is somewhat rounded; the tail is long, and drawn out to a fine point; it is quite destitute of fins, but is armed near its base with a long and sharp, flattened, bony spine, the two sides of which form thin edges, cut into close, acute teeth,—a most formidable weapon. We have one British species, commonly called the Fire-flaire, of which Mr. Couch thus speaks. "The manner in which it defends itself shows its consciousness of the formidable weapon it carries on its tail. When seized or terrified, its habit is to twist its long, slender, and flexible tail round the object of attack, and with the serrated spine tear the surface, lacerating it in a manner calculated to produce violent inflammation." Other authors state that it is capable of striking its weapon with the swiftness of an arrow into its prey or its enemy, when, with its winding tail, it secures its capture.
5. Myliobatina. The Eagle Rays. The pectorals are here greatly extended in breadth in proportion to their length, giving to the fish somewhat of the outline of a bat or a butterfly, dilated to gigantic dimensions. The anterior half of the head is free, and the eyes are placed at the margin of its summit. The teeth are arranged like broad flat paving stones, of regular forms: the tail is still more lengthened and attenuated than in the last sub-family, and is furnished with a serrated spine; it has a small dorsal near its base. Two species of this group are British, though very rare; one of these is the Cephaloptera, already mentioned as attaining colossal proportions, and displaying a fierce voracity in the tropical seas.
Genus Raia. (Linn.)
In this the most numerous genus of the Family, and the only one of any value to man, the disk is rhomboidal, greatly flattened; the tail is moderately slender, generally armed with rows of small spines; there is no notched spear, but two small dorsals near the tip are present, and sometimes the vestige of a caudal; the teeth are flattened, small, arranged in quincunx, the central ones becoming lengthened and pointed with age. The head and neck cannot be externally distinguished from the body, being included on the sides by the fore-part of the pectorals. The body is in general beset with sharp points, or spinous tubercles, sometimes small and few as in the Skate (Raia batis, Linn.); sometimes large and numerous as in the Thornback (R. clavata).
We select the latter species for illustration. It is abundantly common all round the British coasts, as well as on those of western and southern
Europe. It attains a diameter of two feet; is brown above with paler spots, and white beneath. The whole upper surface is rough with minute points, and is studded with an irregular number of large hooked spines. The structure of these is peculiar; each consists of an oval, rather thick disk of white bone, the centre of which rises into a sharp conical point curved backwards, the whole possessing a slight resemblance to one of the prickles on the stem of a rose-bush. A group of small ones of similar form surround each eye, and a row runs down the middle of the back in close series. The others are much larger, and irregularly scattered both over the body and the tail.
The Thornback is much eaten by the poorer classes, both fresh and salted; the females and young are called Maids, and are considered best for the table. The flesh is in best condition in autumn and winter; becoming soft and woolly in spring and summer, which is the spawning season. Great numbers are caught, however, at these times, their approach to the shore rendering their capture more easy.
The acute spines with which so many of the Rays are studded, make them dangerous to handle; no doubt they may be considered as weapons of defence, if not of offence. It is observable that the long and flexible tail is always the most effectively armed: we have already seen how the spine of the Trygon is used; the learned zoologist to whom we are indebted for that information, has also described the defensive action of the Skate. "The point of the nose and the base of the tail are bent upwards towards each other: the upper surface of the body being then concave, the tail is lashed about in all directions over it, and the rows of sharp spines frequently inflict severe wounds."
Family IV. Petromyzonidæ.
(Stone-suckers.)
We have now arrived at the lowest examples of organization among Fishes, and consequently the bottom of the scale formed by the series of animals having an internal skeleton of bone and a vertebrated spine. Throughout the whole of this Order we have seen how the former character has become less and less distinct, the skeleton being cartilaginous instead of bony; in the present Family the latter distinctive mark gradually disappears, the spine in the highest forms being “traversed by a single tendinous cord, filled internally with a mucilaginous fluid, without contractions and enlargements, so that the vertebrae are reduced to cartilaginous rings not easily distinguishable from each other, and, indeed, not cartilaginous through their whole circle,” (Cuvier);–while in the lowest forms (Amphioxus), it is reduced to a simple cartilaginous column or thread, flexible, transparent, and scarcely to be distinguished from the horny pen enveloped in the flesh of some of the Mollusca. Hence it has been disputed whether these minute creatures have a right to a place among Vertebrata; though the preponderance of opinion, founded on dissection and comparison of various organs, is in favour of such a position being assigned to them.
What we have further to say must be considered as applying principally to the more developed members of the Family. They have no pectorals nor ventrals; but foldings of the skin above and below the hinder parts of the body serve the purpose of dorsal, caudal, and anal; destitute, however, of supporting rays. The form is long, slender, and cylindrical, much resembling that of a worm; the mouth consists of a circular fleshy lip, with a cartilaginous ring supporting it. The gills are not comb-shaped fringes, but form sacs or pouches, by the union of two opposite ones along their edges.
These humbly organized members of the great Vertebrate division of animated beings are but few in number, about fourteen species being the whole of those known to naturalists. They are found both in fresh and salt waters, principally in the northern parts of the world. Six of the number are enumerated as British.
Genus Petromyzon. (Linn.)
The Lampreys have a smooth, elongated, cylindrical body like that of an Eel. There are seven gill-apertures on each side; the mouth is circular, and its inner surface is studded with hard, crusted tubercles, answering the purpose of teeth. The tongue, which moves backwards and forwards like a piston, has two rows of small teeth. The skin, elevated in a fold around the extremity of the body, answers to dorsal, caudal, and anal fins.
The generic name applied to these fishes, Petromyzon, signifies Stone-sucker; and refers to a curious habit depending on the structure of the mouth. The animal applying its circular lip to the surface of a stone or other solid body in the water, draws in the piston-like tongue; a vacuum is thus produced in the mouth, while the pressure of the super-incumbent body of water causes the lip to adhere to the stone with immense tenacity, until by the protrusion of the tongue the vacuum is voluntarily destroyed.
It is supposed that the Lamprey resorts to this singular expedient to prevent its being constantly carried down by the current of the rivers in which it lives; its powers of locomotion being feeble. But Sir William Jardine has shown that a much more obvious end is effected by the same means, the formation of a fit receptacle for the deposited spawn. The Lamprey (Petromyzon marinus, Linn.) ascends the rivers of Scotland to breed about the end of June, and remains in them until August. These fishes "are not furnished with any elongation of the jaw, afforded to most of our freshwater fish, to form the receiving furrows at this important season; but the want is supplied by their sucker-like mouth, by which they individually remove each stone. Their power is immense. Stones of a very large size are transported, and a large furrow is soon formed. They remain in pairs, two on each spawning place, and while there employed, retain themselves affixed by the mouth to a large stone."
The curious sucking-mouth is also serviceable to these fishes in enabling them to prey upon other fishes, which otherwise they would be ill-calculated to molest. They are known to attack fishes of large size, by fastening upon their flesh, and while affixed eating away the soft parts down to the bone, with their numerous small rasp-like teeth.
This species is called the Sea Lamprey to distinguish it from another, the River Lamprey, called also Lampern (P. fluviatilis). The latter is a permanent inhabitant of fresh water, but the former only ascends the rivers to spawn. Both are in high repute for the table, but the Lamprey is of much more value than the Lampern, on account of its superior size. It attains two or three feet in length; its ground colour is olive, handsomely spotted and mottled with deep green and dark brown; the edges of the fins are reddish; and the eyes are golden.
The Lamprey is taken in the Severn, near Worcester, and also in the Thames, but only in the summer months. The mode of taking this fish is very simple, and not difficult to one who
has a quick eye and steady hand. By the aid of a long staff armed at the end with several diverging hooks, the fishes are seized from the gravel at the bottom, where on a bright day they may be seen feeding, and are lifted into the boat.
In winter the Lampern affords employment to the Thames fishermen, when other fishes fail. It is taken in large numbers by means of wicker baskets placed across the weirs. Though much valued for the table, the Lampern produces a better remuneration by being sold to the Dutch fishermen, who use it as bait in the Cod fishery. Many thousands are exported alive, preserved in tanks of fresh water, in the course of the winter; and when the produce is divided, the share of each man engaged in the pursuit not unfrequently amounts to forty pounds sterling.
It is said to be an ancient custom for the city of Gloucester to present for the royal table, once every year, a pie of Lampreys, covered with a raised crust. King Henry I. met his death through his fondness for this worm-like fish; his mortal sickness having been produced by eating to excess of Lampreys, after a day spent in hunting.
There are one or two other species of the genus found in our waters, but they are small, and of no importance.
