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.
[Illustration: Fig. 340. Skeleton of the Common Perch.
_a_, the inter-maxillary bone; _b_, the maxillary bone; _d_, the gills;
_c_, the under jaw; _f_, the inter-operculum; _g g_, the vertebral
column; _h_, the pectoral fin; _i_, the ventral fin; _k_ and _l_, the
dorsal fins; _m_, the anal fin; _n_, the caudal fin.]
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.
[Illustration: Fig. 341. Swimming bladder of the Carp.]
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.
[Illustration: Fig. 342. Anatomy of the Carp.
_br_, the branchiæ, or gill openings; _c_, the heart; _f_, the liver;
_vn_, swimming bladders; _ci_, intestinal canal; _o_, the ovarium; _u_,
urethra; _a_, anus; _o'_, oviduct.]
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.
[Illustration: Fig. 343. A Fish's Eye.
_i_, crystallized pupil; _ee'_, cornea; _mm'_, choroid; _h_, posterior
chambers; _c_, optic nerve.]
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]
[Illustration: Fig. 344. Teeth of the Bream.]
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.
[Illustration: Fig. 345. Teeth of the Carp.]
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.
[Illustration: Fig. 346. Teeth of the Trout.]
[Illustration: Fig. 347. Teeth of the Gold-fish Dorada.]
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.
[Illustration: Fig. 348. The Lamprey (Petromyzon marinus).]
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.
[Illustration: Fig. 349. The White Ray (Raia batis).]
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.
[Illustration: Fig. 350. The Lump-fish (Raia clavata).]
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.
[Illustration: Fig. 351. The Cramp-fish (Torpedo marmorata).]
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_.
[Illustration: Fig. 352. The Shark (Carcharius vulgaris).]
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.
[Illustration: Plate XXV.--Shark Fishing.]
"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.
[Illustration: Fig. 353. The Pickled Dog-fish (Acanthias vulgaris).]
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.
[Illustration: Fig. 354. The Hammerhead (Zygæna malleus).]
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.
[Illustration: Fig. 355. The Arctic chimæra.]
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.
[Illustration: Fig. 356. The Common Sturgeon (Acipenser sturio).]
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.]
[Illustration: Plate XXVI.--Sturgeon Fishing on the Volga.]