nature, are facts well known to all. The lowest fish, the little
clear-bodied lancelet, possesses no brain whatever, and no organ
of hearing is developed, while the eyes are at the best of very
simple and rudimentary structure. In other fishes, again, the brain
and nervous system not only acquire a typical development, but
the senses also advance in perfection. The sense of sight is of
perfect kind, the eyes of fishes being adapted for seeing in the
dense medium in which they live; while the sense of smell is also
developed, although, curiously enough, the nostrils, in all except
two kinds of fishes--the hag-fishes and the curious Lepidosiren or
mud-fish--are pocket-like in nature, and do not open backward, as in
higher animals, into the mouth. The sense of taste is not exercised
in a high degree by fishes, and it is interesting to observe that the
sense of touch appears to reside especially in the sides of the body,
on which surfaces a well-marked line--the “lateral line”--may be
observed in most fishes. This lateral line is connected with a series
of canals or sacs abundantly supplied with nerves. The function
of these organs is believed to be that of exercising the sense of
touch; and from the manner in which many fishes swim against objects,
and bring the sides of their bodies in gentle contact with foreign
objects, there would seem to exist strong reasons for supporting the
above idea. That fishes “hear” is a well-known fact. No outer ear is
developed, but an internal ear--the essential part of the organ of
hearing--is found in all fishes except the little lancelet.
While the intelligence or instinct of fishes is not, generally
speaking, of a high order, there are not wanting instances to prove
that these animals may exhibit traits of character sometimes wanting
in higher groups of animals. Any one who has kept gold-fishes must
have noted that in time they become more and more familiar with the
hand that feeds them, and the experience of aquarium keepers goes to
prove that some fishes may even show signs of recognizing friends.
Like the human race, the class of fishes evinces many illustrations
of individuals and groups which differ more or less widely from their
more commonplace neighbors. To some of the more curious of these “odd
fishes” we may next direct attention.
A very singular little group of fishes, for example, is that known to
the naturalist by the name Lophobranchii; this term meaning literally
“tuft-gilled.” Included in this division are two curious families, of
one of which the sea-horses or Hippocampi are the representatives;
while to the other family belong their allies, the pipe-fishes. No
more interesting forms than these two groups can well be selected
from the great class of which they are little-known members. And the
interest with which they are regarded by zoologists extends beyond
the mere investigation of their outside form or appearance; since
they present, in many points of their economy and habits, very marked
deviations from what one may call the ordinary course of fish-life.
Imagine a little body from four to six inches in length, topped
by a head which in outline exactly resembles that of a horse, and
which tapers off below, or rather behind, into a lithe, flexible,
and pointed tail, and we may form a rough idea of the general
appearance of one of the sea-horses. This little body we shall find
to be covered with ganoid plates or scales of hard horny or bony
material, exhibiting ridges and angles all over its surface. Two
large brilliant eyes, each of which may be moved independently of the
other, add to the curious appearance of the head; while to the body
itself may be attached long streamers of sea-weed, serving to conceal
the little beings as they nestle amid their marine bowers, each
looking like some veritable creation of heraldic or mythological kind.
The flexible tail which terminates the body has the important office
of mooring or attaching the fishes to any fixed object. As we see
them in the aquarium, they are generally poised, as it were, on
the tail; the latter being coiled around a bit of sea-weed, while
the erect body and head look warily through the waters of their
miniature sea. When they detach themselves, they swim about in the
erect position by means of the two pectoral or breast fins, which
being placed close to the sides of the neck, project like veritable
ears, and assist in rendering the equine appearance of the head of
still more realistic nature. These fins move with a quick twittering
motion, and propel their possessor swiftly through the water; while
the back-fin, placed toward the hinder extremity of the body, also
assists them in swimming.
Some curious points in the internal structure of the sea-horses
warrant a brief notice. As already stated, the gills of an ordinary
fish are shaped each like a comb; the teeth of the comb being
represented by the delicate processes, each consisting in reality
of a network of blood-vessels, in which the blood is exposed to
the oxygen of the water, and is thus purified. In the sea-horses,
however, the gills do not present this comb-like appearance,
but exist in the form of separated tufts or bunches of delicate
filaments, which spring from the gill-supports or arches. From this
peculiarity the name “tuft-gilled,” already alluded to, is derived,
and the pipe-fishes agree in the structure of the gills with the
sea-horses. Then, also, as most readers are aware, the gills of
ordinary fishes are covered by a horny plate, appropriately named
the gill-cover, and it is by sharply compressing the gills with this
cover that the water used in breathing is ejected from the gills, so
as to make room for a fresh supply. In the sea-horses, however, the
gill-cover is not open or free at its under and hinder edges, but is
firmly attached all round to the neighboring tissues, and so rendered
immovable. At one point in its circumference, however, a small
aperture is left, through which the breathing-water escapes from the
gills.
The sea-horses are found abundantly in the English Channel, around
the coasts of France and Spain, in the Mediterranean Sea, and in the
tropical oceans. Several distinct species are known to zoologists,
but they closely resemble one another in the essential features just
noted. They are lively and intelligent little creatures, and become
familiar in time with their possessors. Fixed by their tails, they
may be seen actively to dart the head at any passing object adapted
for food; while, when they wish to free their bodies from the
attached position, they appear to manœuvre with the chin and head in
order to effect their purpose. Their food appears to consist of small
crustaceans, worms, etc.; and they are known to be especially fond of
such delicate titbits as are afforded by the eggs of other fishes.
Perhaps the most curious part of the history of the sea-horses
relates to their care of the young. Fishes generally take little
or no care of their offspring, and it is therefore the more
surprising to encounter in these little beings a singular example
of parental fidelity and attachment. Nor, as might be expected,
is it the mother-fish who is charged with the task of attending
the young. Contrary to the general rule, the male fish assumes the
part of nurse, and well and faithfully does he appear to discharge
his duties. At the root of the tail in the male sea-horse a
curious little pouch is seen. In this pouch the eggs laid by the
females--which want the pouch--are deposited, and are therein duly
hatched. Nor does the parental duty end here; for after the young are
hatched and swim about by themselves, they seek refuge in the pouch
during the early or infantile period of their life whenever danger
threatens them. This procedure forcibly reminds one of the analogous
habits of the kangaroos and their young; but the occurrence is the
more remarkable in the lower and presumably less intelligent fish.
Some experiments made on the sea-horses seem to demonstrate the
existence of a more than ordinary degree of attachment to the young.
Thus when a parent-fish was taken out of the water, the young
escaped from the pouch; but on the parent being held over the side of
the boat, the young at once swam toward him, and re-entered the pouch
without hesitation. Some authorities have not hesitated to express
an opinion that the young are nourished within the pouch by some
fluid or secretion of its lining membrane. But further observation is
certainly necessary before this latter opinion can be relied upon.
The pipe-fishes are very near neighbors of the sea-horses, and derive
their name from the thin elongated shape of their bodies, together
with the fact that the jaws are prolonged to form a long pipe-like
snout, at the extremity of which the mouth opens. These fishes are
very lively in all their movements, and dart through the water so
quickly that in many cases the eye is unable to follow them. Like the
sea-horses, the male pipe-fishes protect and tend their progeny, and
exhibit an equal attachment to their young.
These latter features are also well exemplified by the familiar
sticklebacks of our ponds and streams. The latter fishes actually
build nests for the reception and care of their eggs, the nests being
made chiefly or solely by the males; while on the latter, during the
process of hatching and in the upbringing of the young, devolves
the chief care of protecting and looking after the welfare of the
progeny. These instances of the care and duties which devolve on the
males, instead of on the mother-parents, appear to reverse the more
natural order which almost universally obtains in the case of both
lower and higher animals.
Of the oddities which fish-life presents, probably none are more
remarkable than the archer or shooter fishes (Toxotes), which inhabit
the seas of Japan and of the Eastern Archipelago. When kept in
confinement, these fishes may be seen to shoot drops of water from
their elongated jaws at flies and other insects which attract their
attention. They have been observed to strike their prey with unerring
aim at distances of three or four feet. Another notable species
of shooting-fishes is the Chætodon. This latter form possesses a
prominent beak or muzzle, consisting of the elongated jaws; and from
this beak, as from the barrel of a rifle, the fish shoots its watery
missiles at the insects which alight on the vegetation fringing its
native waters.
The old saying which compares great helplessness to the state of a
“fish out of water” does not always find a corroborative re-echo
in natural history science. As every one knows, different fishes
exhibit very varying degrees of tenacity to life when removed from
their native element. Thus a herring dies almost immediately on
being taken out of water; while, on the other hand, the slippery
eels will bear removal from their habitat for twenty-four hours or
longer; and we have known of blennies--such as the shanny (Blennius
pholis)--surviving a long journey by post of some forty-eight hours’
duration, when packed amid some damp sea-weed in a box.
But certain fishes are known not merely to live when taken out of
water, but actually of themselves, and as part of their life and
habits, to voluntarily leave the water and disport themselves on
land. Of such abnormal fishes, the most famous is the climbing perch
or Anabas scandens of India, which inhabits the Ganges, and is also
found in other Asiatic ponds and rivers. These fishes may be seen to
leave the water and to make their way overland, supporting themselves
in their jerking gait by means of their strong spiny fins. They
appear to migrate from one pool to another in search of “pastures
new,” especially in the dry season, and when the water of their
habitats becomes shallow.
The Hindu name applied to these fishes means “climbers of trees”;
and although statements have been made both by travelers and natives
that the climbing perch has been found scaling the stems of trees,
these accounts, we fear, must be regarded as of equal value with the
native belief that the fishes fall in showers on the land from the
skies. Of the power of the fishes to live for five or six days out
of water, however, no doubt can be entertained; and their ability to
support life under these unwonted conditions is explained by the fact
that certain bones of the head are curiously contorted so as to form
a labyrinth, amid the delicate recesses of which a supply of water is
retained, for the purpose of keeping the gills moist.
Another group of fishes, also inhabiting India, and possessing powers
of existing “out of water,” is the Ophiocephalidæ (“snake-headed”);
a family allied to the Mullet group. It would appear, from some
observations on these fishes, that they are enabled not only to
live, like the climbing perch, out of water, but that they die if
kept below the surface of the water even for a comparatively short
time. Thus when an Ophiocephalus and a carp were placed together
in a vessel of water, a net being placed about two inches from the
surface, the carp swam, as might be expected, freely and continuously
below the surface, while the Ophiocephalus made vigorous efforts to
attain the surface, for the purpose of inhaling air directly from the
atmosphere. When not allowed to reach the surface, the Ophiocephali
died, suffocated, in periods varying from twenty minutes to two
hours. The explanation of the power possessed by the latter fish,
of being able to live out of water, resides in the fact that these
fishes possess two cavities in the throat, in which blood is purified
by the inhalation of atmospheric air. Thus the Ophiocephalus not only
can exist out of water, but escape from that medium must, in fact, be
viewed as an absolute necessity for the normal life of the animal.
The climbing perch appears also to exhibit this latter peculiarity of
requiring to escape periodically from the water, for this fish, like
the Ophiocephalus, may be actually drowned, if kept from obtaining a
supply of atmospheric air.
The curious Lepidosirens or mud-fishes, which occur in the Gambia of
Africa and the Amazon of South America, exhibit a greater peculiarity
of structure, which still more completely fits them for living out
of water. In the great majority of fishes, a curious sac or bag
known as the _swimming_ or _air bladder_ is found. The use of this
structure in ordinary fishes is to alter the specific gravity of the
animals; and, by the compression or expansion of the air or gases
it contains, to enable them to sink or rise in the water at will;
but it would also appear that indirectly it may aid in the breathing
of all fishes which possess the organ. In the mud-fishes, however,
the air-bladder becomes divided externally into two sacs, while
internally each sac exhibits a cellular structure resembling that
seen in the lungs of higher animals, with which structures, in fact,
the swimming-bladder of fishes actually corresponds. Then also this
elaborate air-bladder of the mud-fish communicates with the mouth
and throat by a tube, which corresponds to a windpipe. The nostrils
of the mud-fishes further open backward into the mouth; while, as
already mentioned, in all other fishes, save one genus, the nostrils
are simple, closed, pocket-like cavities. And it may lastly be noted
that the Lepidosirens are in addition provided with true gills, like
their ordinary and more commonplace neighbors.
These remarks serve to explain the “reason why” these fishes can
exist for months out of water. Thus, on the approach of the hot
season, the mud-fishes leave their watery homes and wriggle into the
soft mud of their native rivers. Here they burrow out a kind of nest,
coiling head and tail together; and as the mud dries and hardens,
the fishes remain in this temporary tomb; breathing throughout the
warm season like true land-dwellers, by means of the lung-like
air-bladder. When the wet season once more returns, the fishes are
aroused from their semi-torpid state by the early rains moistening
the surrounding clay; and when the pools and rivers once more attain
their wonted depth, the Lepidosirens emerge from their nests, seek
the water, breathe by means of their gills, and otherwise lead a true
aquatic existence. Another fish, the Ceratodus or “Barramunda” of
Australian rivers, possesses a similarly modified air-bladder, and is
thus enabled to breathe independently of its gills.
With such a combination of the characters of land and water animals,
it is little to be wondered at that the true position of the
mud-fishes and their neighbors in the zoological scale should have
formed a subject for much discussion. They appear, however, to be
true fishes, and not amphibians (or frog-like animals); and they
therefore may legally occupy a prominent position among the oddities
of their class.
Other curious beings included among the fishes are the so-called
globe-fishes (Diodon, etc.), which derive their name from their
power of distending their bodies with air at will; and their bodies
being usually provided with spines, they may be judged to present a
rather formidable front to any ordinary adversary in their expanded
condition. Then also we have the curious trigger-fishes (Balistes),
so named from the prominent pointed spine in front of the first
back-fin; this spine firmly holding its erect position until the
second spine or fin-ray be depressed, when the first spine is
released by mechanism resembling that of the trigger of a gun. The
obvious use of such an apparatus is clearly of a defensive kind; and
it is remarkable to find that man has imitated and reproduced, in one
of his common mechanical contrivances, a structure existing in all
its natural perfection in the fish.
Oddities in the way of curious fishes can receive no
better illustration than that afforded by the very curious
“telescope-fishes” of China. These beautiful little fishes are
kept alive in many of our large aquaria. At first sight the
telescope-fishes might be mistaken for the familiar gold-fishes,
but a cursory inspection of their appearance at once shows the
peculiarities of structure which have earned for these creatures
their distinctive name. The eyes are seen to be singularly prominent,
and protrude from the head to a marked extent, while they also
present certain alterations in intimate structure. The fins,
moreover, are double, this conformation being well exemplified in
the large and prominent tail-fin. The exact nature of these fishes
has been discussed by the French Academy of Sciences, in the records
of which it is stated that the Chinese have cultivated these fishes
from an ordinary species of the carp race, and that the peculiar
conformation of the eyes results from a diseased state, which, by
being transmitted from one generation to another, has become at last
a stable and definite character of the animals. This very probable
explanation of the origin of these peculiar eyes is supported by the
fact that certain carps inhabiting the canal Saint Martin at Paris
were found to possess prominent eyes; and a like appearance has been
observed in carps living in rivers into which the water of drains had
been allowed to flow.
WONDERS OF THE SHORE
--CHARLES KINGSLEY
See, on the shore, a shell bed, quite large, but comely enough to
please any eye. What a variety of colors and forms are there, amid
the purple and olive wreaths of wrack, and bladder-weed, and tangle
(ore-weed they call it in the south), and the delicate green ribbons
of the Zostera (the only English flowering plant which grows beneath
the sea). What are they all? What are the long, white razors? What
are the delicate green-gray cimeters? What are the tapering brown
spires? What the tufts of delicate yellow plants like squirrels’
tails and lobsters’ horns, and tamarisks, and fir-trees, and all
other finely cut animal and vegetable forms? What are the groups of
gray bladders, with something like a little bud at the tip? What are
the hundreds of little pink-striped pears? What those tiny babies’
heads covered with gray prickles instead of hair? The great red
star-fish, which the Ulster children call “the bad man’s hands”; and
the great whelks, which the youth of Musselburgh know as roaring
buckies, these we have seen before; but what, oh what, are the red
capsicums?
Yes, what are the red capsicums? and why are they poking, snapping,
starting, crawling, tumbling wildly over each other, rattling about
the huge mahogany cockles, as big as a child’s two fists, out of
which they are protruded? Mark them well, for you will perhaps never
see them again.
That red capsicum is the foot of the animal contained in the
cockle-shell. By its aid it crawls, leaps, and burrows in the sand,
where it lies drinking in the salt water through one of its siphons
and discharging it again through the other. Put the shell into a rock
pool, or a basin of water, and you will see the siphons clearly.
But I suppose your eyes will be rather attracted by that scarlet
and orange foot which is being drawn in and thrust out to a length
of nearly four inches, striking with its point against any opposing
object, and sending the whole shell backward with a jerk. The point,
you see, is sharp and tongue-like, only flattened, not horizontally,
like a tongue, but perpendicularly, so as to form, as it was
intended, a perfect sand-plow, by which the animal can move at will
either above or below the surface of the sand.
Enough of Cardium tuberculatum. Now for the other animals of the
heap; and first, for those long, white razors. They, as well as the
gray cimeters, are solens, razor-fish (Solen siliqua and S. ensis),
burrowers in the sand by that foot which protrudes from one end,
nimble in escaping from the Torquay boys, whom you will see boring
for them with a long iron screw on the sands at low tide. They are
very good to eat, these razor-fish; at least for those who so think
them; and abound in millions upon all our sandy shores.
Now for the tapering brown spires. They are Turritellæ, snail-like
animals (though the form of the shell is different), who crawl and
browze by thousands on the beds of Zostera, or grass wrack, which
you see thrown about on the beach, and which grows naturally in two
or three fathoms of water. Stay: here is one which is “more than
itself.” On its back is mounted a cluster of barnacles (Balanus
Porcatus), of the same family as those which stud the tide-rocks
in millions, scratching the legs of hapless bathers. Look at the
mouth of the shell; a long gray worm protrudes from it, which
is not the rightful inhabitant. He is dead long since, and his
place has been occupied by one Sipunculus Bernhardi, a wight of
low degree who connects “radiate” with annulate forms--in plain
English, sea-cucumbers with sea-worms. But however low in the scale
of comparative anatomy, he has wit enough to take care of himself;
mean, ugly, little worm as he seems. For, finding the mouth of the
Turritella too big for him, he has plastered it up with sand and mud
(Heaven alone knows how), just as a wry-neck plasters up a hole in
an apple tree when she intends to build therein, and has left only a
round hole, out of which he can poke his proboscis. A curious thing
is this proboscis, when seen through the magnifier. You perceive a
ring of tentacles round the mouth, for picking up I know not what;
and you will perceive, too, if you watch it, that when he draws it
in, he turns mouth, tentacles, and all inward, and so down into his
stomach, just as if you were to turn the finger of a glove inward
from the tip till it passed into the hand; and so performs, every
time he eats, the clown’s as yet ideal feat of jumping down his own
throat.