CEPHALOPODOUS MOLLUSCA.
"Monstrum horrendum, informe, ingens." VIRGIL.
The highest class of Molluscs is the Cephalopoda, which has been divided
by Professor Owen into two Orders, _Tetrabranchiata_, or animals having
four branchiæ, and the _Dibranchiata_, having two branchiæ. The first
Family of the _Tetrabranchiata_, having the Ammonitidæ, contains the
fossil Turrilites and Ammonites. The second Family, _Orthoceratidæ_,
contains the fossil Gomphoceras and Orthoceras. The third Family,
_Nautilidæ_, contains Nautilus.
The name Cephalopoda, as already stated, is taken from the position of
the feet, which are inserted in the anterior part of the head: in Greek
κεφαλὴ, _head_, and ποῦς-ποδὸς, _foot_.
The Cephalopodous Molluscs are indeed highly organised for Molluscs, for
they possess in a high degree the sense of sight, hearing, and touch.
They appear with the earlier animals which present themselves on the
earth, and they are numerous even now, although they are far from
playing the important part assigned to them in the early ages of organic
life upon our planet. The _Ammonites_ and _Belemnites_ existed by
thousands among the beings which peopled the seas during the secondary
epoch in the history of the globe.
This great class is otherwise divided into two orders: _Tentaculiferous
Cephalopods_, those furnished with strong fleshy tentacula, and
_Acetabuliferous_, or sucker-bearing.
TENTACULIFEROUS CEPHALOPODS.
In place of bearing simple suckers (_Acetabula_), like the last order of
Cephalopods, this group is furnished with true organs of prehension, or
tentacles. They differ from the first group chiefly in their more
numerous arms, which are quite tentaculiferous, having neither suckers
nor capsules, and by having an external shell. The number of living
species is extremely limited; for this group of animals belongs
peculiarly to the earlier ages of our globe, is gradually becoming
extinct, and presents in our days only some rarer species, when we
compare them with the prodigious numbers of these beings which animated
the seas of the ancient world. In fact, the only living type of the
order is the nautilus, which has a singular resemblance in form to the
argonaut.
The shell of this mollusc has a regularly convoluted form, the last
whorl being equal to all the others. It is divided internally into
numerous cells, formed by transverse partitions, concave in front and
perforated towards the centre, and forming a kind of funnel, which gives
passage to a respiratory siphon.
In the last cell of the shell (Fig. 312) is the animal, covered by its
mantle, which covers the walls of the cells. When it contracts itself it
is protected by a sort of triangular and fleshy hood. Numerous
contractile tentacles, re-entering into the sheath, some of them
furnished with numerous lamellæ, surround the head, which is, besides,
scarcely distinguished from the body. The head bears two great
projecting eyes, planted upon a peduncle.
[Illustration: Fig. 312. Nautilus pompilius (Linnæus), showing the
interior of the lower cell, to which the animal is fixed.]
Like Sepia and Octopus, the mouth of the Nautilidæ is armed with
mandibles, fashioned like the parrot's beak; the branchiæ are four in
number. The circulating system consists of a ventricle and auricle, and
the locomotive tube is protected in its whole length. The shell is
secreted by the outer edge of the mantle, while its posterior extremity
fashions the walls of the cells, which indicate the successive growth of
the individual.
The siphon, which traverses all the chambers, receives and protects the
ligament, by the aid of which the Cephalopod is retained in the last
chamber of the shell.
Fig. 313 is the same section, with the last cell empty, and with the
perforations through which the siphon passes.
The Nautilidæ are inhabitants of the Indian Ocean and the sea round the
Molucca Islands. In swimming, their head and tentacles are projected
from out of the shell. In walking on rocks they drag themselves along
the ground, the body upwards, the head and tentacles beneath. They
betake themselves frequently to miry cavities frequented by fish. It is
a much more common occurrence to find the empty than inhabited shells of
the Nautilus at sea. This, probably, arises from its exposure to the
attacks of crustaceans and other marine carnivora. This seems to be
proved by the mangled appearance of the edges in the empty shells thus
met with.
[Illustration: Fig. 313. Nautilus pompilius (Linnæus) showing the lower
cell and the partition giving passage to the siphon.]
[Illustration: Fig. 314. Shell of Nautilus pompilius (Linnæus).]
The Pearly Nautilus, _Nautilus pompilius_ (Fig. 314), is so common on
the Nicobar coast that the inhabitants salt and dry its flesh, and store
them as provisions. Its shell attains about eight inches in its greatest
height. This shell is still used by the Hindoo priests as their conch or
shell, with which they summon their devotees to worship. It is nearly
round, smooth, transversely blazed in its posterior part, and entirely
white anteriorly. A very fine nacre is yielded by this mollusc, which is
much used in ornamental cabinet-work. The Orientals make drinking-cups,
on which they engrave designs and figures, which form graceful objects.
Similar vases were formerly shaped in Europe, which found their way into
great houses. In our days they are generally consigned to cabinets of
curiosities and the shops of dealers in articles of virtù.
Owen's second order, _Dibranchiata_, contains six families; the first is
_Spirulidæ_, containing the curious Spirula, that little gem amongst
oceanic shells. The second family is _Sepiadæ_, containing Belemnosis
and Sepia. The third is _Belemnitidæ_; the fourth, _Teuthidæ_; the
fifth, _Octopodidæ_; and the sixth, _Argonautidæ_.
ACETABULIFEROUS CEPHALOPODA.
To this group belong the cuttle-fish, squids, and argonauts, among
existing species, and the Belemnites among the fossil species. Some of
these creatures are large, and essentially flesh-eaters, or carnivorous;
and, if we may believe all that has been written respecting them, very
formidable ones. Listen to Michelet, while he paints the warlike humour
of these inhabitants of the deep:--"The Medusæ and Molluscs," says this
popular author, "are generally innocent creatures, and I have lived with
them in a world of gentle peace. Few flesh-eaters among them; those even
which are so, only kill to satisfy their wants, living for the most part
on life just commenced--on gelatinous animals, which can scarcely be
called organic. From this world grief was absent. No cruelty and no
passion. Their little souls, if mild, were not without their ray of
aspiration towards the light, and towards what comes to us from heaven,
and towards that love, revelling in that changing flame which at night
is the light of the deep. It is now, however, necessary to describe a
much graver world: a world of rapine and of murder; from the very
beginning, from the first appearance of life, violent death appeared;
sudden refinement, useful but cruel, purification, of all which has
languished, or which may linger or languish, of the slow and feeble
creation whose fecundity had encumbered the globe.
"In the more ancient formations of the old world we find two
murderers--a nipper and a sucker. The first is revealed to us by the
imprint of the trilobite, an order now lost, the most destructive of
extinct beings. The second subsists in one gigantic fragment, a beak
nearly two feet in length, which was that of a great sucker or
cuttle-fish (_Sepia_). If we may judge from such a beak, this monster,
if the other parts of the body are in proportion, must have been
enormous; its ventose, invincible arms, of perhaps twenty or thirty
feet, like those of some monstrous spider. The sucker of the world, soft
and gelatinous! it is himself. In making war on the molluscs he remains
mollusc also; that is to say, always an embryo. He presents the strange,
almost ridiculous, if it was not also terrible, appearance of an embryo
going to war; of a foetus furious and cruel, soft and transparent, but
tenacious, breathing with a murderous breath, for it is not for food
alone that it makes war: it has the wish to destroy. Satiated, and even
bursting, it still destroys. Without defensive armour, under its
threatening murmurs there is no peace; its safety is to attack. It
regards all creatures as a possible enemy. It throws about its long
arms, or rather thongs, armed with suckers, at random." Such is the
somewhat exaggerated picture which the eloquent historian and poet draws
of the Molluscous Cephalopod, and it must be admitted that there is a
basis of truth in this, as well as in the more recent one painted by
Victor Hugo, in his eloquent book, "Les Travailleurs de la Mer." Where,
however, there is so much of the fictitious floating about, it will be
our endeavour to eliminate facts only.
FAMILY OF THE SEPIADÆ.
The body of the cuttle-fish (_Sepia_) is thus a very singular structure,
somewhat reminding us of certain species of polyps. We find a body or
abdominal mass, hand ahead, separated by compression, sufficiently
marked. The body is covered by the mantle, which has the form of a sac
opened only in front by a transverse cleft. The head has a projecting
and well-developed eye on each side; it is surmounted by a sort of
fleshy funnel, which is divided by four pairs of tentacles. At the
bottom of this tentacular funnel is the mouth; and from the anterior
opening in the mantle a tube issues, which is wide at its base.
The Sepiadæ have eight arms rising from the crown of the head armed with
four rows of suckers, two long slender tentacles with broadly-expanding
ends, and stalked suckers; eyes moving in their sockets, and body
broadly ovate in Sepia.
If we study the general aspect of the animal more closely, we find that
the tentacles--which serve at once as organs of locomotion for swimming,
for creeping, and as prehensile organs for seizing and retaining its
prey--are conical, very long, and all of the same form. Each of them has
towards its axis a longitudinal canal, which encloses a great nerve,
which is also surrounded with muscular fibres, arranged in rays. The
suckers, already described, occupy all the internal surface of the eight
tentacular arms, which are arranged in two rows, having the form very
nearly of a semi-spherical capsule. Of these suckers, each arm of the
cuttle-fish carries about two hundred and forty, the total number being
nearly a thousand. The mouth we have already described, in Dr. Roget's
words: "The teeth move vertically, much as the cutting edge of the two
blades of a pair of scissors move upon each other, tearing the prey by
the assistance of their hooked terminations."
The tongue is covered on its upper part by a thick horny bed, bristling
in the centre with a series of recurving teeth, while its edge is armed
with three other erect teeth, which are slender and hooked. The
oesophagus is long and slender. At the abdomen the gullet expands into a
sort of frill, to which succeeds a gizzard, with strong fleshy walls;
and, finally, a very short intestine, which directs itself forward,
terminating on the median line of the body. Towards the anterior parts
is a cavity, of which a few words must be said. It occupies the free
space comprised between the exterior surface of the abdomen and the
internal face of the mantle; and here the respiratory organs, namely,
the _branchiæ_, are lodged. Here, also, are the reproductive and
excretory organs.
The branchiæ, which are two in number, are voluminous, but short,
tufted, and leaf-like. The branchial cavity can dilate and contract
itself alternately. It communicates externally by two openings: the one,
fashioned into a cleft, receives, while the other, which is prolonged
into a tube, serves to eject, the water, and becomes a powerful organ of
locomotion.
The inspiration of the animal is thus made by a cleft in the mantle, and
expiration by the tube: the renewal of the respirable liquid acts as a
sort of sucking and forcing pump, at the surface of the lamellar
branchials. The cuttle-fish, in short, will be at no loss to reply to
the question of the Don Diego of Corneille--
"Rodrique, as-tu du cœur?"
for they have three hearts. The two first are placed at the end of the
branchiæ. With each beat of the pulse the venous blood is brought from
all parts of the body, and propelled through each gill or branchiæ.
Vivified by respiration in the internal tissue of the branchiæ, it is
carried by the veins into the third heart, situated upon the median line
of the body; and now the regenerated fluid is again distributed
throughout the rest of the economy.
Not to oppress the reader with anatomical details, we shall just remark
that the gaze of the cuttle-fish is decided and threatening. Its
projecting eyes and golden-coloured iris are said to have something of
fascination in them. The animal seems able even to economise the power
of its glance, being able to cover its eyes from time to time by
contracting the skin which surrounds them, and bringing the two
translucent eyelids with which it is furnished closer together.
The cuttle-fishes are essentially aquatic and marine animals. We find
them in every sea in all parts of the world; but they are most
formidable in warm countries. They have a great predilection for the
shore. During their youth they associate in flocks; but with age they
fly from association, and retire into the clefts and hollows of the
rocks. The old cuttle-fish is only found in rugged and rocky places,
bristling with naked, pointed rocks, which have been worn by the waves,
but generally in places only a few feet below the level of low water.
"How often," says D'Orbigny, "have we not observed the cuttle-fish in
his favourite retirement! There, with one of his arms cramped to the
walls of its dwelling, it extends the other towards the animals which
pass at its gate, embraces them, and by its power renders useless all
their efforts to disengage themselves."
If we observe a cuttle-fish when it is what may be called walking,
either on land or at the bottom of the sea, it will be seen to walk on
one side, its head downwards, its mouth touching the ground, the arms
extended and grappling some supporting object, and drawing the body
forward; at the same time the arms at the opposite side are contracted
and folded up, so as to assist by a contrary movement. On shore the
movement of these animals is very slow. On the other hand, they swim
very rapidly, assisted by all their arms, and aided by the water ejected
from the locomotive tube, their movement being most frequently
backwards, the body first, the six superior arms placed horizontally,
the two others brought together above: the first help to sustain them in
their horizontal position, the last to guide them, inclining to the
right or left as the animal changes its direction.
The cuttle-fishes feed on crustaceans, fishes, and also on shelled
molluscs--every kind of animal, in fact, which comes within their reach;
so that it is readily taken by means of the flesh of fish or
crustaceans, in which a strong hook is concealed. They live for five or
six years, and reproduce by eggs, which are large, and generally found
in clusters, known to fishermen under the name of _sea-grapes_.
Like the zoophytes, they possess the property of redintegration, already
described, being able to reproduce any arm that may be destroyed. There
is another singular peculiarity which the cuttle-fish shares with man.
Under the influence of strong emotion the human face becomes pale, or
blushes, and in some individuals it is said to become blue. This has
always been supposed to be an attribute of humanity; but the cuttle-fish
shares it with our race. Yielding to the impressions of the moment, the
cuttle-fish suddenly changes colour, and, passing through various tints,
it only resumes its familiar one when the cause of the change has
disappeared. They are, in fact, gifted with great sensibility, which
reacts immediately upon their tissues, these being extremely elastic and
delicate. Sudden changes of colour are produced--changes which far
exceed the same phenomena in man. Under the influence of passion or
emotion man is born to blush, but under no sort of excitement does he
cover himself with pustules; this the cuttle-fish does: it not only
changes colour, but it covers itself with little warts. "Observe a
cuttle in a pool of water," says D'Orbigny, "as it walks round its
retreat--it is smooth, and of very pale colour. Attempt to seize it, and
it quickly assumes a deeper tint, and its body becomes covered on the
instant with warts and hairs, which remain there until its confidence is
entirely restored."
The following fact is abbreviated from the "Natural History and Fishery
of the Sperm Whale." Mr. Beale had been searching for shells among the
rocks in Bonin Island, and was much astonished to see at his feet a most
extraordinary-looking animal, crawling back towards the surf which it
had just left. It was creeping on its eight legs, which, from their soft
and flexible nature, bent considerably under the weight of its body, so
that it was just lifted by an effort above the rocks. It appeared much
alarmed, and made every attempt to escape. Mr. Beale endeavoured to
stop it by putting his foot on one of its tentacles, but it liberated
itself several times in spite of all his efforts. He then laid hold of
one of the tentacles with his hand, and held it firmly, and the limb
appeared as if it would be torn asunder in the struggle. To terminate
the contest, he gave it a powerful jerk; it resisted the effort
successfully, but the moment after the enraged animal lifted a head with
large projecting eyes, and loosing its hold of the rocks, suddenly
sprang upon Mr. Beale's arm, which had been previously bared to the
shoulder, and clung to it with its suckers, while it endeavoured to get
the beak, which he could now see, between the tentacles, in a position
to bite him. Mr. Beale describes its cold slimy grasp as extremely
sickening, and he loudly called to the captain, who was also searching
for shells, to come to his assistance. They hastened to the boat, and he
was released by killing his tormentor with a boat-knife, when the arms
were disengaged bit by bit. Mr. Beale states that this Cephalopod must
have measured across its expanded arms about four feet, while its body
was not bigger than a large hand clenched. It was the species called the
rock-squid by whalers.
These formidable and curious Cephalopods, the Μαλάκια of Aristotle,
_Mollia_ of Pliny, and _Cephalophora_ of De Blainville, have the mantle,
according to Cuvier, united beneath the body, thus forming a muscular
sac which envelopes the whole viscera. The body is soft and fleshy,
varying much in form, being sub-spherical, sub-elliptical, and
cylindrical, the sides of the mantle in many species extending into
fleshy fins. The head protrudes from the muscular sac, and is distinct
from the body; it is gifted with all the usual senses, the eyes in
particular, which are either pedunculate or sessile, being large and
well developed. The mouth is anterior and terminal, armed with a pair of
horny or calcareous mandibles, which bear a strong resemblance to the
bill of a parrot, acting transversely, one upon the other. Its position
is the bottom of a sub-conical cavity, forming the base of numerous
fleshy tentacular appendages which surround it, and which are termed
arms by some writers. These appendages in the great majority of living
species are provided with suckers, _acetabula_ (cupping-glass-like
appendages), by means of which the animal moves at the bottom of the
sea, head downwards, or attaches itself to its prey. These suckers are
armed or unarmed with a long, sharp, horny claw. In the unarmed
acetabulum, the mechanism for adhesion is well described by Dr. Roget:
"The circumference of the disk," says this writer, "is raised by a soft
and turned margin; a series of long slender folds of membrane covering
corresponding fascicula of muscular fibre converge from the
circumference towards the centre of the sucker, at a short distance from
which they leave a circular aperture; this opens into a cavity which
widens as it descends, and contains a cone of soft substance rising from
the bottom of the cavity, like the piston of a syringe. When the sucker
is applied to the surface, for the purpose of adhesion, the piston,
having previously been raised so as to fill the cavity, is retracted,
and a vacuum produced, which may be still further increased by the
retraction of the plicated portion of the disk." Here we have an
excellent description of the apparatus for holding on. When the animal
is disposed to let go his hold, according to Professor Owen, "the
muscular arrangement enables the animal to push forward the piston, and
thus in a moment destroy the vacuum which retraction had produced."
In the case of the armed Cephalopods (_Onychoteuthis_), Professor Owen
remarks, "that there are circumstances in which even the remarkable
apparatus described by Dr. Roget would be insufficient to fulfil the
offices in the economy of Nature for which the Cephalopod was created,
and that in species which have to contend with the agile mucous-clad
fishes more powerful organs of prehension are superadded to the suckers,
so that in the calamary the base of the piston is, he remarks, enclosed
in a horny hoop, the outer and anterior margin of which is developed
into a series of sharp curved teeth, which can be firmly pressed into
the flesh of a struggling prey by the contraction of the surrounding
transverse fibres, and can be withdrawn by the action of the retracting
fibres of the piston. "Let the reader," the professor adds, "picture to
himself the projecting weapon of the horny hoop developed into a long,
curved, sharp-pointed claw, and these weapons clustered at the expanded
terminations of the tentacles, and arranged in a double alternate series
along the internal surface of the eight muscular feet, and he will have
some idea of the formidable nature of the carnivorous cephalopod." The
professor notices another structure which adds greatly to the prehensile
powers of the uncinated Cephalopods. "At the extremities of the long
tentacles a cluster of small, simple, unarmed suckers may be observed at
the base of the expanded part. When these latter suckers are applied to
one another, the tentacles are firmly locked together at that part, and
the united strength of both the elongated peduncles can be applied to
drag towards the mouth any resisting object which has been grappled by
the terminal hooks. There is no mechanical contrivance which surpasses
this structure; art has remotely imitated it in the fabrication of the
obstetrical forceps, in which either blade can be used separately, or,
by the interlocking of a temporary blade, be made to act in
combination."--_Cyc. of Anat._
The third Family, _Belemnitidæ_, contains Belemnitella and Belemnites,
and other genera of less importance; they are all now extinct, although
once numerous as species.
The cuttles, _Sepia_ (Fig. 315), have the body fleshy and depressed,
continued into a sac, and bordered on all its length on both sides with
a wing or narrow fin, the larger short and flat, broader than it is
long, with two large eyes, covered by an expansion of the skin, which
becomes transparent over a surface equal to the diameter of the iris,
and furnished with inferior contractile eyelids.
[Illustration: Fig. 315. Sepia officinalis (Linnæus).]
This head is surmounted by ten tentacular arms or feet, eight of which
are short and conical, and two long and slender, terminating in a sort
of spatula. These arms are all armed with suckers, and are perfectly
retractile. They surround a mouth armed with two horny jaws not unlike
the beak of a parrot.
The skin of the cuttle-fish presents in one vast hollow, occupying all
the extent of the back, a great calcareous part, the form and structure
of which is quite characteristic of this genus. It is known as the
cuttle-bone (Fig. 316). This bone is used for many purposes; among
others, it is used in a powdered state as a dentifrice. It is sometimes
suspended in the cage with captive birds, that they may whet their beaks
on it, and collect phosphate of lime for the formation and repair of
their bones. The osselet is oval or oblong, some provided with a
slightly salient point. The upper part is surrounded with a horny or
cretaceous margin, and presents in the centre a combination of spongy
cells.
Most of the Cephalopods secrete a blackish, inky fluid, to which some
allusion has been made, but the uses of which, in the economy of the
animals, is imperfectly known. The cuttles have considerable quantities
of this liquor, which is contained in a sort of sac or ink-purse, placed
low down in the abdomen. When the animal is pursued or threatened with
danger it discharges a jet of the fluid, which renders the water thick
and muddy, and permits it to escape in the obscurity from its pursuers.
It appears that the cuttle-fish avails itself of this stratagem when
left accidentally ashore. It is related of an English officer, that,
having dressed for dinner, and having some time to spare, he proceeded
along the shore on his favourite search for objects of natural history.
He reached a hollow rock in which a cuttle-fish had established its
quarters; he soon detected the animal, which looked at him for some time
with its great prominent eyes; in short, they watched each other with
fixed attention. This mute contemplation came to a sudden and unexpected
termination by the discharge of a voluminous jet of inky fluid, which
covered the officer, which was the more unfortunate, since he was in his
summer dress of white trousers.
[Illustration: Fig. 316. Internal bone of Sepia officinalis.]
[Illustration: Fig. 317. Sepia tuberculosa (Lamarck).]
The ink of the cuttle-fish is a favourite pigment, used in water-colour
painting under the name of _sepia_. It is truly indestructible; and the
hard and black substance found in the sac of fossil species of
cuttle-fish when diluted with water produces a brilliant sepia. This
property of the inky fluid was well known to the Romans, who used it in
making ink. It was long supposed to be the chief ingredient in China
ink; but a recent traveller, Mr. Seebold, who has visited the
manufactory, and investigated the subject, has revealed the true process
by which it is prepared.
The cuttle-fish affects the sea-shore; they are along-shore molluscs.
The flattened form of their bodies is favourable to a coasting life, by
permitting them to rest easily on the bottom. Still they do not remain
all the year round upon the coast. The cold in temperate regions, and
the opposite reason in warm regions, leads them to withdraw from the
shore, to which they only return in the spring. They are rarely seen in
the Channel in winter, but with the vernal sun they appear in large
shoals. What is the mechanism by which these animals are moved? When the
cuttle-fish wishes to swim rapidly and backwards, they advance in the
water by means of the locomotive tube, sending back the ambient liquid.
When they wish to approach a prey slowly in order to seize it, they swim
by the aid of their fins and arms. In order to swim backwards, they
contract the arms provided with tentacles, and spread out horizontally
the arms without tentacles.
The cuttles are flesh-eaters, and tolerably voracious. They feed
themselves upon fishes, molluscs, and crustaceans. They are true aquatic
brigands, who kill not to feed themselves, but for the sake of killing;
and Nature, by a just equilibrium, applies to them the _lex talionis_.
They fall victims, in their turn, to the vengeful jaws of the porpoises
and dolphins. Such is the terrible law of Nature: some must die that
others may live. Michelet gives us a glimpse of the manner in which the
dolphins dispose of the cuttle-fish in his "Livre de la Mer." "These
lords of the ocean," he says, "are so delicate in their tastes that they
eat only the head and arms, which are both tender and of easy digestion.
They reject the hard parts, and especially the after-part of the body.
The coast at Royan, for example, is covered with thousands of these
mutilated cuttle-fish. The porpoises take most incredible bounds, at
first to frighten them, and afterwards to run them down; in short, after
their feast, they give themselves up to gymnastics."
In the spring the cuttle-fishes deposit their eggs, but without
abandoning them. On the contrary, they exhibit a truly maternal care,
taking much trouble to attach them to some submarine body, in which
position the temperature of the water serves to hatch the eggs. _Sepia
officinalis_, for example, chooses, at the moment of laying, a stem of
_Fucus_, a foot of _Gorgonia_, or some other solid submarine body not
less in dimensions than the little finger, and there it firmly attaches
its eggs, which are pear-shaped, that is, pointed at one extremity,
while a long _lanière_ of a gelatinous nature, flat and black in
appearance, with which they are provided, surrounds the solid body like
a ring. Each female lays and attaches in this manner from twenty to
thirty eggs, which are clustered together somewhat like a bunch of fine
black grapes (Fig. 318). About a month after this the eggs are hatched.
The colours of _Sepia officinalis_ vary considerably; but in general it
may be remarked that the males are ornamented with deeper colours than
the females. Transverse bands of a blackish brown furrow their backs,
and diminish their breadth. Outside of these bands are small spots of a
vivid white: very near the edge there is a white border, accompanied
inside with a second edging of a beautiful violet. The median and
anterior parts of the body are spotted here and there; beneath, a
whitish tint with reddish speckles prevails.
[Illustration: Fig. 318. Sepia officinalis (Linnæus).]
The cuttle-fishes are found on every shore, and wherever they are found
they are eaten, for their flesh is savoury. They are usually fried or
boiled. They form an excellent bait for large ground-fish, such as
dog-fish, rays, and congers, which are fond of their flesh.
Thirty species are known, and they are chiefly characterised by the
arrangement and form of the cupules of the arms. _Sepia officinalis_ is
common on the shores of the ocean from Sweden to the Canaries, and in
all parts of the Mediterranean.
The fourth family, _Teuthidæ_, contains _Loligopsis_, _Cranchia_, and
_Loligo_.
The _Calmars_ were described by Aristotle under the name of Γείφις,
and by Pliny under that of _Loligo_, which is still retained as the
generic name. Their popular name of Calmar (calamar in old French) is
taken from their resemblance to certain species of ink-holders. Oppian,
who endowed the argonaut with wings, believed that the calmar also
could take to the air, in order to avoid his enemies. Nevertheless,
he was much puzzled how to give the form and functions of a bird to a
fish. Themistocles, by way of insult to the Eretrians, likened them
to calmars, saying they had swords and no hearts. Athenæus, a Greek
physician before Galen, dwelt upon the nourishing properties of the
flesh of the calmar.
Common enough in temperate regions, the calmars abound in the seas of
the Torrid zone: they are gregarious, and live in numerous shoals, their
bands taking every year the same direction, their emigration proceeding
from temperate to warm regions--nearly the same course as that followed
by the herrings and pilchards.
The calmars, like the cuttles, propel themselves backwards through the
water with great velocity, driving back the water by means of their
locomotive tube, moving with such vigour and promptitude that they have
been known to throw themselves out of the water, falling on the shore or
on the deck of a vessel. They only appear momentarily on the shore, and
only sojourn there to deposit their eggs, which are gelatinous in
substance, about the level of the lowest tides. The body in the calmars
is longer than in the cuttle-fish, cylindrical in shape, and terminating
in a point, having two lateral fins, which occupy the lower half or
third of its body.
[Illustration: Fig. 319. Loligo vulgaris, with its pen, or internal bone
(Lamarck).]
[Illustration: Fig. 320. Loligo Gahi (D'Orbigny).]
In the common calmar, _Loligo vulgaris_ (Fig. 319), and the _Loligo_
_Gahi_ (Fig. 320), we have two extreme forms represented, both taken
from the magnificent work of MM. D'Orbigny and Ferussac, on the
_Cephalopodes acetabulifores_. These molluscs are whitish-blue and
transparent, covered with spots of bright red. The osselet is
lanceolate--that of the male elongated and somewhat resembling a
feather, that of the female much broader and more obtuse. Their head is
short, furnished with two large projecting eyes; the mouth is surrounded
with ten arms, provided with suckers, two of these being much longer
than the others, having peduncles or foot-stalks.
The internal bone of the calmar differs much from that of the cuttles;
it is thin, horny, transparent, and somewhat resembling a feather, from
a portion of which the _barbs_ have been removed. Their food consists
chiefly of small fishes and molluscs. With the greater fishes and
cetaceæ they carry on constant war. They are caught and used for various
purposes; along the coast they are eaten; the fishermen use them as
bait, especially in fishing for cod.
It is no easy task to separate the real from the fabulous history of the
Cephalopods. Aristotle and Pliny have alike assisted, by their
marvellous relations, to throw that halo of wonder round it which the
light of modern science has not altogether dispelled. Pliny the Ancient
relates the history of an enormous cuttle-fish which haunted the coast
of Spain, and destroyed the fishing-grounds. He adds that this gigantic
creature was finally taken, that its body weighed seven hundred pounds,
and that its arms were ten yards in length. Its head came by right to
Lucullus, to whose gastronomical privileges be all honour. It was so
large, says Pliny, that it filled fifteen amphoræ, and weighed seven
hundred pounds also.
Some naturalists of the Renaissance, such as Olaüs Magnus and Denis de
Montfort, gave credit--which they are scarcely justified in doing--to
the assertions of certain writers of the north of Europe, who believed
seriously in the existence of a sea-monster of prodigious size which
haunted the northern seas. This monster has received the name of the
_Kraken_. The Kraken was long the terror of these seas; it arrested
ships in spite of the action of the wind, sails, and oars, often causing
them to founder at sea, while the cause of shipwreck remained
unsuspected. Denis de Montfort gives a description and representation of
this Kraken, which he calls the Colossal Poulpe, in which the creature
is made to embrace a three-masted ship in its vast arms. Delighted with
the success which his representation met with, Denis laughed at the
credulity of his contemporaries. "If my Kraken takes with them," he
said, "I shall make it extend its arms to both shores of the Straits of
Gibraltar." To another learned friend he said, "If my entangled ship is
accepted, I shall make my Poulpe overthrow a whole fleet."
Among those who admitted the facetious history of the Kraken without a
smile, there was at least one holy bishop, who was, moreover, something
of a naturalist. Pontoppidan, Bishop of Bergen, in Norway, in one of his
books assures us that a whole regiment of soldiers could easily
manœuvre on the back of the Kraken, which he compares to a floating
island. "Similior insulæ quan bestiæ," wrote the good Bishop of Bergen.
In the first edition of his "System of Nature," Linnæus himself admits
the existence of this colossus of the seas, which he calls _Sepias
microcosmos_. Better informed in the following edition, he erased the
Kraken from his catalogue.
The statements of Pliny respecting the Colossal Poulpe, like those of
Montfort about the Kraken, are evidently fabulous. It is, however, an
undisputed fact that there exists in the Mediterranean and other seas
cuttle-fish--a congenerous animal--of considerable size. A calmar has
been caught in our own time, near Nice, which weighed upwards of thirty
pounds. In the same neighbourhood some fishermen caught, twenty years
ago, an individual of the same genus nearly six feet long, which is
preserved in the Museum of Natural History at Montpellier. Péron, the
naturalist, met in the Australian seas a cuttle-fish nearly eight feet
long. The travellers Quoy and Gaimard picked up in the Atlantic Ocean,
near the Equator, the skeleton of a monstrous mollusc, which, according
to their calculations, must have weighed two hundred pounds. M. Rung
met, in the middle of the ocean, a mollusc with short arms, and of a
reddish colour, the body of which, according to this naturalist, was as
large as a tun cask. One of the mandibles of this creature, still
preserved in the Museum of the College of Surgeons, is larger than a
hand.
In 1853 a gigantic cephalopod was stranded on the coast of Jutland. The
body of this monster, which was dismembered by the fishermen, furnished
many wheelbarrow loads, its pharynx, or back part of the mouth, alone
being as large as the head of an infant. Dr. Steenstrup, of Copenhagen,
who published a description of this creature under the name of
_Architeuthis dux_, shows a portion of the arm of another cephalopod,
which is as large as the thigh-bone of a man. But a well-authenticated
fact connected with these gigantic cephalopods is related by Lieutenant
Bayer, of the French corvette Alecton, and M. Sabin Berthelot, French
Consul at the Canary Islands, by whom the report is made to the Académie
des Sciences.
The steam-corvette Alecton was between Teneriffe and Madeira when she
fell in with a gigantic calamary, not less--according to the
account--than fifteen mètres (fifty feet) long, without reckoning its
eight formidable arms, covered with suckers, and about twenty feet in
circumference at its largest part, the head terminating in many arms of
enormous size, the other extremity terminating in two fleshy lobes or
fins of great size, the weight of the whole being estimated at four
thousand pounds; the flesh was soft, glutinous, and of reddish-brick
colour.
The commandant, wishing in the interests of science to secure the
monster, actually engaged it in battle. Numerous shots were aimed at it,
but the balls traversed its flaccid and glutinous mass without causing
it any vital injury. But after one of these attacks the waves were
observed to be covered with foam and blood, and, singular thing, a
strong odour of musk was inhaled by the spectators. This musk odour we
have already noticed as being peculiar to many of the Cephalopods.
The musket-shots not having produced the desired results, harpoons were
employed, but they took no hold on the soft impalpable flesh of the
marine monster. When it escaped from the harpoon it dived under the
ship, and came up again at the other side. They succeeded at last in
getting the harpoon to bite, and in passing a bowling hitch round the
posterior part of the animal. But when they attempted to hoist it out of
the water the rope penetrated deeply into the flesh, and separated it
into two parts, the head with the arms and tentacles dropping into the
sea and making off, while the fins and posterior parts were brought on
board: they weighed about forty pounds.
[Illustration: Plate XXIV.--Gigantic Cuttle-fish caught by the French
Corvette Alecton, near Teneriffe.]
The crew were eager to pursue, and would have launched a boat, but the
commander refused, fearing that the animal might capsize it. The object
was not, in his opinion, one in which he could risk the lives of his
crew. PL. XXIV. is copied from M. Berthelot's coloured representation of
this scene. "It is probable," M. Moquin-Tandon remarks, commenting on
M. Berthelot's recital, "that this colossal mollusc was sick or
exhausted by some recent struggle with some other monster of the deep,
which would account for its having quitted its native rocks in the
depths of the ocean. Otherwise it would have been more active in its
movements, or it would have obscured the waves with the inky liquid
which all the Cephalopods have at command. Judging from its size, it
would carry at least a barrel of this black liquid, if it had not been
exhausted in some recent struggle."
"Is this mollusc a calmar?" asks the same writer. "If we might judge
from the figure drawn by one of the officers of the Alecton during the
struggle, and communicated by M. Berthelot, the animal had terminal
fins, like the calmars; but it has eight equal arms, like the
cuttle-fish. Now the calmars have ten, two of them being very long. Was
this some intermediate species between the two? Or must we admit, with
MM. Crosse and Fisher, that the animal had lost its more formidable
tentacles in some recent combat?"[13]
The fifth family, _Octopodidæ_, contains _Eledone_, _Octopus_,
_Pinnoctopus_, _Cirroteuthis_, _Philonexis_, and _Scærgus_.
The _Octopoda_, without tentacles, have eight long arms, united at the
base by a web; the suckers in two rows, which are sessile; the eyes
fixed; shell, two short stiles enclosed in the mantle; the body united
to the head by a broad neck-band; no side-fins; shell internal and
rudimentary in the British species; body oval, warty, and without fins,
in _Octopus_; small and oblong, arms tapering and webbed, and suckers in
a single row, in _Eledone_ (Fig. 321).
[Illustration: Fig. 321. Eledone, Octopus vulgaris (Lamarck).]
In his great work, Professor Owen proposes to divide the Cephalopods
into two groups, which he calls _Dibranchiata_, characterised by the
presence of two branchiæ, which would bring together all the naked
Cephalopods, including Sepia, Loligo, Octopus, Kassia, and Ommastrephos;
and _Tetrabranchiata_, having four branchiæ, to which the _Nautilus_,
and most of the fossil Cephalopods, such as the _Ammonites_, belong.
Most of the first group are represented in the British seas, but the
second are altogether absent.
[Illustration: Fig. 322. Octopus macropus (Risso).]
[Illustration: Fig. 323. Octopus brevisses (D'Orbigny).]
[Illustration: Fig. 324. Octopus horridus (D'Orbigny).]
The _Decapoda_ are of all sizes. Dr. Grant describes the body, or
mantle, of _Sepiola vulgaris_, found on our coast, as measuring about
six lines in length, and as much in breadth, while the head measures
four lines in length, and, from the magnitude of the eyes, must be equal
in breadth with the body. In _Onychoteuthis_, distinguished for its
uncinated suckers, they are found of the size of a man. In Cook's first
voyages, the naturalists to the expedition, "Banks and Solander," to
quote Professor Owen's account, "found the dead carcase of a gigantic
species of this kind floating in the sea between Cape Horn and the
Polynesian Islands, in 30° 44' S. lat., and 110° 10' W. long. It was
surrounded by sea birds, which were feeding on its remains. From the
parts of this specimen which are still preserved in the Hunterian
Museum, and which have always strongly excited the attention of
naturalists, it must have measured at least six feet from the end of the
tail to the end of the tentacles."
In the genus _Eledone_ the arms are reunited at their base by a very
short membrane, with only a single row of suckers. The two best-known
species of this group inhabit the Mediterranean. The one is _Eledone
moschatus_, known in Italy under the name of Muscardino, from the strong
odour of musk which it emits, even after death and desiccation; the
other is _Eledone cirrhosus_, a small species, bluish-grey on the back,
and whitish under the belly.
The habits of _Eledone moschatus_ have been carefully studied by M.
Verany. The able naturalist of Nice preserved many of these animals
during a month, in a great aquarium, noting their habits. When in a
state of tranquillity, the _Eledone_ clung to the sides of the glass
tank in which it was kept. Its head is then inclined forwards, with the
sac hanging behind; the locomotive tube, turned upwards, presents the
orifice between the arms. In this state the animal is yellowish in
colour, its eyes dilated, its inspirations regular. But if irritated, a
remarkable change takes place: its body assumes a fine maroon colour,
and it is covered with numerous tubercles; the eye becomes contracted, a
column of water is forcibly ejected from the locomotive tube at the
aggressor, and the respiration becomes precipitate, jerky, and
irregular. The creature would take a strong inspiration, and, having
collected its force, suddenly throw a jet of water to a distance of more
than three feet. This state of passion, which the slightest touch is
sufficient to produce, endures for half an hour or more. When it ceases,
the animal resumes its form and primitive colours; but the least shock
impressed on the water is sufficient to give it a deeper tint, which
passes like a flash of lightning over the skin of this singular proteus.
The Eledone sleeps by day as well as by night, attaching itself in its
sleep to the walls of its prison, leaving its arms to float around, the
two inferior ones extending backwards, and the sac inclining over them;
its eyes are then contracted, and in part covered by the eyelids. Its
respiration is regular and slow, and any ejection of water very rare;
its colour is then of a livid grey, and vinous red below, with whitish
spots, while the brown spots have now entirely disappeared. While still
asleep, it is watchful and attentive to all the dangers which could
surprise it. The extremities of the arms floating round its body are
ready to announce the approach or contact of any other object. Even the
most delicate touch is perceived immediately, and it shrinks from the
hand which seeks to approach. Under every circumstance the Eledone
exhales a strong odour of musk, which it preserves long after death.
When the Eledone swims, which it rarely does unless pressed by some
urgent necessity, it carries the sac in advance, the arms floating
behind--the six upper ones being on a horizontal line, the two others
approaching each other below. Thus arranged, it presents, in consequence
of its flattened form, a very large resisting surface to the water, its
progress being due to the alternate dilatation and contraction of the
body, which expels the water through the locomotive tube, and by
reaction produces a rapid and jerking movement. Sometimes the arms aid
the movement; the eyes of the animal are then much dilated, and its
colour a clear livid yellow, finely shaded with red, and covered with
bright spots.
[Illustration: Fig. 325. Pinnoctopus corolliformis (D'Orbigny).]
[Illustration: Fig. 326. Cirrotheutis Mittleri (Eschricht).]
It is a singular fact that the creature notably changes colour under any
exertion, so that the animal at rest and in motion are two different
beings. When walking under water the tube is directed behind, its arms
are spread out, the head is raised, and the body slightly inclined
forward; its mantle is then of a pearly grey, and the spots take the
tint of wine lees. When at rest the shades disappear.
The _Pinnoctopus_ (Fig. 325), another genera of this family, have the
body oblong, with lateral expansions, as represented in the accompanying
figure.
In _Cirrotheutis_ the arms are completely united in their whole extent
by a thin membrane furnished with cirri, which alternate with certain
suckers arranged in one row. Only one species of this genera is known as
an inhabitant of northern seas, which is represented in Fig. 326.
The sixth family, _Argonautidæ_, contains only _Argonauta_.
The Argonauta, or Paper-nautilus. Floating gracefully on the surface of
the sea, trimming its tiny sail to the breeze, just sufficient to ruffle
the surface of the waves, behold the exquisite living shallop. The
elegant little bark which thus plays with the current is no work of
human hands, but a child of Nature: it is the Argonaut, whose tribes,
decked in a thousand brilliant shades of colour, are wanderers of the
night in innumerable swarms on the ocean's surface.
The marine shell which Linnæus called the Argonaut enjoyed great renown
among the ancient Greeks and Romans. It was the subject of graceful
legends; it had inspired great poets; it occupied the attention of
Aristotle, who called it the _Nautilus_ and _Nauticos_, and of Pliny,
who called it _Pompylius_. Few animals, indeed, have been so celebrated,
so anciently known. The Greek and Roman poets saw in it an elegant model
of the ship which the skill and audacity of the man constructed who
first braved the fury of the waves; in the words of the poet, "armour of
triple oak and triple brass covered the heart of him who first confided
himself in a frail bark to the relentless waves:"
"Illi robur et æs triplex
Circa pectus erat, qui fragilem truci
Commisit pelago ratem
Primus...."
_Horace_, I. Car. iii. l. 9.
To meet the Pompylius was, according to the superstitious Roman, a
favourable presage. This little oceanic wanderer, in spite of the
capricious waves, was a tutelar divinity, who guarded the navigator in
his course, and assured him of a happy passage. Listen to the immortal
author of the first Natural History of Animals, the philosophical
Aristotle. "The Nautilus Polyp," says the learned historian, "is of the
nature of animals which pass for extraordinary, for it can float on the
sea; it raises itself from the bottom of the water, the shell being
reversed and empty, but when it reaches the surface it readjusts it. It
has between the arms a species of tissue similar to that which unites
the toes of web-footed birds. When there is a little wind, it employs
this tissue as a sort of rudder, letting it fall into the water with the
arms on each side. On the approach of the least danger it fills its
shell with water, and sinks into the sea."
Pliny gives it the name of Pompylius, and, after the example of
Aristotle, explains how it navigates, by elevating its two first arms, a
membrane of extreme tenuity stretching between them, while it rows with
the others, using its median arm as a rudder. The Greek poet, Oppian,
who lived in the second century of our era, and to whom we are indebted
for Poems on Fishing (_Halieutica_) and the Chase (_Cynegetica_), says
of it: "Hiding itself in a concave shell, the Pompylius can walk on
land, but can also rise to the surface of the water, the back of its
shell upwards, for fear that it should be filled. The moment it is seen,
it turns the shell, and navigates it like a skilful seaman: in order to
do this, it throws out two of its feet like antennæ between which is a
thin membrane, which is extended by the wind like a sail, while two
others, which touch the water, guide, as with a rudder, the house, the
ship, and the animal. If danger approaches, it folds up its antennæ, its
sail, and its rudder, and dives, its weight being increased by the water
which it causes to enter the shell. As we see a man who is victor in the
public games, his head circled by a crown, while vast crowds press
around, so the Pompylius have always a crowd of ships following in their
track, whose crews no longer dread to quit the land. O fish justly dear
to navigators! thy presence announces winds soft and friendly: thou
bringest the calm, and thou art the sign of it."
Oppian carried his admiration a long way. That the Argonaut is an
animated skiff is agreed on all hands; but, in making it almost a
bird--in according to it at once the faculty of gracefully navigating
the sea and floating in the atmosphere as an inhabitant of the regions
of air--he was passing the limits permissible to poetic license.
But the properties of the Nautilus has not alone struck the imagination
of the Greeks and Romans; it also attracted the attention of the
Chinese, who call it the boat-polyp. Rumphius informs us, that in India
the shell fetches a great price (Fig. 327). Women consider it a great, a
magnificent ornament. In their solemn fêtes dancers carry one of these
shells in the right hand, holding it proudly above their heads. Nor did
it require the dithyrambic praises with which the ancients have
surrounded it to recommend it to the admiration of modern naturalists.
Without exaggerating the graceful attributes with which it is gifted, it
is at once one of the most curious objects in Nature.
[Illustration: Fig. 327. Shell of Argonauta argo (Linnæus).]
[Illustration: Fig. 328. The Argonauta argo (Linnæus).]
Its body (Fig. 328) is ovoid in form, and it is furnished with eight
tentacles, covered with a double row of suckers. Of these tentacles, six
are narrow and slender, tapering to a point towards the extremity, while
two of them expand toward the extremity in the form of wings or sails.
These are all folded up when in a state of repose. The body itself is
contained in a thin, white, and fragile univalve shell, which is oval,
flattened on the exterior, but rolled up in a spiral in the interior,
the last turn of the shell being so large as to give it something of the
form of an elegantly-shaped shallop. Singularly enough, the body of the
animal does not penetrate to the bottom of the shell, nor is it attached
to it by any muscular ligament; nor is the shell moulded exactly upon
it, as is the case with most other testaceans.
What does all this imply? Is the Argonaut a parasite? a fraudulent
disinheritor? a vile assassin, who, having surprised and killed the
legitimate proprietor of the shell, has installed itself in its place,
and in the proper house of its victim? Such crimes are not without
example in the natural history of animals--witness the proceedings of
the curious _hermit crab_, whose proceedings we shall glance at in a
future chapter. The parasitic character of the Nautilus was long
conceded by naturalists; but recent facts have corrected this opinion.
We have collected their shells, of all dimensions and of all ages,
inhabited always by the same animal, whose size is always proportioned
to the volume of the shell. More than that, it is now known that in the
egg of the Nautilus the rudiments of the shell exist. M. Chenu tells us,
that under the microscope Professor Duvernoy discovered a distinct shell
contained in the embryo. Sir Everard Home asserts the contrary; and no
opportunity presented itself for the complete solution of the question,
until Poli was placed by the King of Naples in a position to solve it.
The piscina of Portici was placed at his disposal. He witnessed the
curious mechanism by which the egg is expelled from the uterus, having a
shell, and satisfied himself, by following their development day by day,
that the shell existed in the embryo, and grew with the animal. He
satisfied himself also that the opinion enunciated by Aristotle, that at
no point did the animal adhere to the shell, was perfectly true.
Finally, in the curious series of experiments carried on by Madame
Power, in the port of Messina, the fragments of the frail bark of the
mollusc, which were broken off in taking it, were restored in a few
days, having been reproduced. It is, therefore, quite demonstrated that
the Nautilus, like other testaceous molluscs, itself secretes and
constructs its shell--its diaphanous skiff. The reader, however, must
not flatter himself that he can witness with his own eyes from the
shore, in our narrow channel, the charming picture of the Nautilus
painted by poets and natural historians: they never come near the shore.
They are timid and cautious creatures, dwelling almost always in the
open sea. They live in families, some hundreds of miles from the shore;
and it is during the night, or at most in the fading light of sunset,
that they assemble together to pursue their gambols on the surface of a
tranquil sea.
[Illustration: Fig. 329. Argonauta papyracea, as it swims by means of
its locomotive tube.]
However reluctant we may be to destroy the marvellous fictions of
ancients and moderns, we are compelled to declare that there is no truth
in the often-repeated statement that the Nautilus uses its palmated arms
as oars or sails. In order to swim on the surface, it comports itself as
all other Cephalopods do. It uses neither oars nor sails, and the
palmate arms only serve to envelop and retain its hold on its frail
shell. Its principal apparatus of progression is the _locomotive tube_
with which it is furnished, in common with all Cephalopods, and which is
in the Nautilus very long. Aided by this apparatus, it ejects the water
after it has served the purpose of respiration, and, in doing so,
projects itself against the liquid, as it were. While it advances
through the water under this impulse, its pendent arms, elongated and
reunited in bundles, extend the whole length of the shell. Fig. 329
shows the position of the different parts of the animal when it thus
breasts the waves. These arms are also powerful aids when the animal
creeps on the ground at the bottom of the sea.
[Illustration: Fig. 330. Argonauta papyracea in its shell.]
When the animal is disturbed it retires completely into its shell. From
that moment, the equilibrium being changed, the shell is overturned, and
the animal is nearly invisible. If frightened, it entirely submerges
itself, and sinks to the bottom.
These little beings share with other Cephalopods the strange faculty of
changing colour under the influence of some vivid impression; but their
graceful and delicate organization redeems them from the charge we have
brought against the cuttles. The Nautilus can blush, turn pale, and show
through its transparent shell its body changing in sudden shades; but it
never exhibits those bristling, unpleasant tubercles, the hideous
inheritance of the larger and coarser Cephalopods--the tyrants of the
sea.
The male Argonauts are very small, often not a tenth part of the size of
the females, which alone possess the shells.
The Nautilus carries its egg in the shell, and the little ones are also
hatched in this floating cradle. Four species are at present known: the
species described by Aristotle and Pliny, and the more ancient
naturalists; namely, _A. argo_, or _papyracea_ (Figs. 327 and 329),
which are inhabitants of the Mediterranean as well as the Indian Ocean
and the Antilles. Two others, _A. tubercula_, belonging exclusively to
the Indian Ocean, and _A. baillant_, which is met occasionally in the
Pacific and Atlantic Oceans.
* * * * *
The nautilus belongs to the section of Octopoda, and the class of
Acetabuliferous Cephalopods, having, as the name indicates, eight feet,
from ὀκτὼ, _eight_, and ποῦς, _foot_; at the same time the body
is entirely fleshy, and without fins. The genera of cuttles (_Sepia_)
and Calmars (_Loligo_) belong to another section of the same class;
namely, the Decapoda, because they have ten feet and a sort of internal
osselet, with fins, &c.
THE DISTRIBUTION OF THE MOLLUSCA.
We have thought it better to treat this subject in a separate chapter,
for its vast and complicated nature renders it otherwise difficult to
handle, except in a space which would exceed the limits of this work.
The different genera of the organic world are peculiar to, or most
frequent in, certain localities, and even species and varieties have
their limits. This habit pervades the entire range of organisms, from
the lowest plants to man, whose qualities are to a great extent the type
of the locality he inhabits. The geography of the Mollusca is perhaps
the best known to science. The labours of Mr. Louis Agassiz, Dr.
Sclater, and Professor Edward Forbes, have done much towards giving us a
clear idea of zoological geography. Climate alone is insufficient to
account for the distribution of animals: some higher cause rules here.
But while we admit this, still we must acknowledge that climate exerts
considerable influence in modifying the qualities of species.
The distribution of the Mollusca may be considered from three points of
view. First, as regards _geography_; second as regards _depth_; and
third as regards _time_; the last belongs to geology.
We shall now survey the principal divisions of the ocean; the line of
demarcation being drawn, not by latitude or longitude, but by genera and
species.
The Mollusca of the Arctic seas are well known to show considerable
analogy with those of the later Tertiary periods of Europe. Hence the
great interest connected with their comparison, as it affords,--provided
we are satisfied with this line of argument,--a proof that an Arctic
climate formerly existed in temperate regions. It is the northern Drift
of which we are speaking. Even when species are found living in Britain
identical with those of the Arctic regions, still there is often a
difference in the form or size of British and Arctic specimens; certain
species, such as _Cyprina Islandica_, being comparatively small in the
south of Britain, larger in Shetland, and attaining their greatest size
in Iceland.
The countries included in the Arctic molluscan province are Lapland,
Iceland, Greenland, the west coast of Davis' Straits, and Behring's
Straits. About two hundred species are enumerated by the various Arctic
voyagers, as found in these seas; of these about one-half are peculiar
to these seas, and the other half are either found living in the
temperate regions of Europe, or in their so-called glacial strata.
The Boreal province includes the North Atlantic, from Nova Scotia to
Iceland, and from thence to Faroe, Shetland, and the Norway coast.
The number of species is very large; and more than one-half are common
both to Scandinavia and the North American coast, while a great number
also are found on the British coast.
The province called Celtic by Professor Edward Forbes embraces the
coasts of Britain, Sweden, and Denmark.
Our British mollusca are about seven hundred in number; those bearing
shells are above five hundred. Of these about thirty are peculiar to
Britain. The shells of the Baltic are identical with those of this
province.
The Lusitanian province stretches from Madeira and the Canaries to the
coasts of Spain and Portugal, and includes also the Mediterranean. But
as one might expect, on close examination, the Mollusca in so large an
area differ so widely that we are forced to admit the existence of great
divisions.
The number of species found on the coast of Madeira by Mr. McAndrew was
one hundred and fifty-six, of which forty-four per cent. were identical
with British species, and eighty-three found near the Canaries.
The shells of the Mediterranean are six hundred in number, but it is
probable that more extensive dredging will result in great accessions
being made to this list. A very small number of species only are
identical with those now found in the West Indies.
Nine genera are peculiar to the Mediterranean.
In the character of its shells, the Black Sea resembles the
Mediterranean, but does not contain much more than a tenth of the number
of its species. The number of shells found on the Spanish and Portuguese
coasts is much smaller than one would expect, and can only be attributed
to the scanty explorations that have been made. As we might expect, the
number of species identical with those of Northern Europe is much
greater on the Atlantic than on the Mediterranean coast of Spain.
The sea of Aral, and the Caspian, contain a few peculiar species; but
they have been so little explored, that it is premature, we think, to
form them into a province. The proportions of salt contained in these
seas is much less than in the ocean.
The west of Africa affords a considerable number of fine shells; the
species most numerous being those of Murex, Conus, and Clavatula.
The south African province contains four hundred species; the
characteristic genera are Terebratella, Chiton, Patella, Trochus,
Fissurella, Cypræa, and Conus. A large number of these species are not
found elsewhere.
The Indo-Pacific province stretches from Australia to Japan; the
greater part of the east coast of Africa; the Red Sea; Persian Gulf; the
Asiatic coast, and the islands of the Indian Archipelago.
The molluscs of the Red Sea remind us of those of India; the percentage
of those found also in the Mediterranean being much less. The shells of
the Persian Gulf are but little known; one species, the brindled cowry
(_Cypræa princeps_), has been sold for fifty pounds.
The seas of New Zealand and Australia have been formed into a province.
As might be anticipated, their mollusca have little in common with those
of the rest of the globe.
The Japonic province includes the coast of Japan and the Corea.
The Aleutian province, the centre of which may be taken to be the
Aleutian islands, shows great analogy with the Boreal province of the
west, a considerable number of the shells being identical--a fact
especially interesting when we consider that very few species are found
common to both the south-eastern and south-western coasts of America.
The Californian province is very distinct from that of Panama; the most
numerous genera found there, are Chiton, Acmæa, Fissurella, Trochus, and
Purpura.
The marine shells of Panama are upwards of thirteen hundred; the region
included stretches from the Gulf of California to Peru. For our
knowledge of this province we are much indebted to the researches of Dr.
P. P. Carpenter, who has catalogued six hundred and fifty-four species,
as found at Mazattan.
The Peruvian province contains a long list of species, and extends from
Callao to Valparaiso.
The Magellanic province includes the extreme south of America and the
Falkland Islands. Many genera, the species of which are usually small,
here reach an enormous size, and afford, in many cases, the chief animal
food consumed by the quadrupeds and human population of that wild and
desolate coast.
The Patagonian province extends from St. Catharina to Point Melo on the
east coast.
The number of species found also in the Falkland Islands is very small;
but a large number are identical with Brazilian species; yet the
majority are peculiar.
The Caribbean province extends from Brazil to the West Indies, and
includes, also, the northern coast of South America and the Gulf of
Mexico; a total of fifteen hundred species is enumerated by Professor
Adams as belonging to the province.
The Transatlantic province, or that on the coast of the United States,
does not afford a large number of species, only two hundred and thirty
being known; of these, only fifteen are found in Europe.
The study of the terrestrial and fresh-water mollusca affords even
better grounds for their division into provinces; but we shall not enter
into it here, as it belongs to the Land World.
* * * * *
We shall now say a few words on the depth of the sea, or ocean, in which
Mollusca are found.
The observations of Milne Edwards, Audonin, and Professor Edward Forbes,
have led to the division of the sea into four zones.
The deep sea Coral zone, from fifty to one hundred fathoms; the
Coralline zone from fifteen to fifty fathoms; the Laminarian zone, which
stretches from fifteen fathoms to low water; and the Littoral zone,
between high and low water marks. The great stronghold of Crania,
Thetis, Neæra, Yoldia, Dentalium, and Scissurella, is in the deep sea
Coral zone; while Buccinum, Fusus, Pleurotoma, Natica, Aporrhais,
Philine, and Velutina, which are among the most ravenous and predatory
of molluscs, are found in the Coralline zone. They attack the bivalves,
whose shells among the relics of former seas, as in those of the
present, show evidence of an assault and a murder.
The principal genera of the Laminarian zone are the Nudibranchiata,
Aplysia, Trochus, Nacella, Rissoa, and Lacuna, which feed so much on the
seaweed of this region.
The Littoral zone, which being accessible as the tide recedes, is best
known, affords Cardium, Mytilus, Tellina, Solen, Trochus, Patella,
Littorina, and Purpura; or in plain English, cockles, mussels,
razor-fish, limpets, periwinkles and tingles;--species which are the
first to attract our attention, and which are so much used for food.
FOOTNOTES:
[Footnote 13: Is it necessary to say that even this account--apparently
so well authenticated, not to speak of the representation drawn on the
spot--should be taken "cum grano salis?"--ED.]