INSTINCTS, HABITS, AND ADAPTATIONS
=The Habits of Fishes.=--The habits of fishes can hardly be summarized
in any simple mode of classification. In the usual course of fish-life
the egg is laid in the early spring, in water shallower than that in
which the parents spend their lives. In most cases it is hatched as
the water grows warmer. The eggs of the members of the salmon and cod
families are, however, mostly hatched in cooling waters. The young
fish gathers with others of its species in little schools, feeds on
smaller fishes of other species or of its own, grows and changes until
maturity, deposits its eggs, and the cycle of life begins again, while
the old fish ultimately dies or is devoured.
=Irritability of Animals.=--All animals, of whatever degree of
organization, show in life the quality of irritability or response to
external stimulus. Contact with external things produces some effect
on each of them, and this effect is something more than the mere
mechanical effect on the matter of which the animal is composed. In the
one-celled animals the functions of response to external stimulus are
not localized. They are the property of any part of the protoplasm of
the body. In the higher or many-celled animals each of these functions
is specialized and localized. A certain set of cells is set apart for
each function, and each organ or series of cells is released from all
functions save its own.
=Nerve-cells and Fibres.=--In the development of the individual animal
certain cells from the primitive external layer or ectoblast of the
embryo are set apart to preside over the relations of the creature
to its environment. These cells are highly specialized, and while
some of them are highly sensitive, others are adapted for carrying
or transmitting the stimuli received by the sensitive cells, and
still others have the function of receiving sense-impressions and of
translating them into impulses of motion. The nerve-cells are receivers
of impressions. These are gathered together in nerve-masses or ganglia,
the largest of these being known as the brain, the ganglia in general
being known as nerve-centres. The nerves are of two classes. The one
class, called sensory nerves, extends from the skin or other organ of
sensation to the nerve-centre. The nerves of the other class, motor
nerves, carry impulses to motion.
=The Brain, or Sensorium.=--The brain or other nerve-centre sits
in darkness, surrounded by a bony protecting box. To this main
nerve-centre, or _sensorium_, come the nerves from all parts of the
body that have sensation, the external skin as well as the special
organs of sight, hearing, taste, and smell. With these come nerves
bearing sensations of pain, temperature, muscular effort--all kinds
of sensation which the brain can receive. These nerves are the sole
sources of knowledge to any animal organism. Whatever idea its brain
may contain must be built up through these nerve-impressions. The
aggregate of these impressions constitute the world as the organism
knows it. All sensation is related to action. If an organism is not to
act, it cannot feel, and the intensity of its feeling is related to its
power to act.
=Reflex Action.=--These impressions brought to the brain by the sensory
nerves represent in some degree the facts in the animal's environment.
They teach something as to its food or its safety. The power of
locomotion is characteristic of animals. If they move, their actions
must depend on the indications carried to the nerve-centre from the
outside; if they feed on living organisms, they must seek their food;
if, as in many cases, other living organisms prey on them, they must
bestir themselves to escape. The impulse of hunger on the one hand
and of fear on the other are elemental. The sensorium receives an
impression that food exists in a certain direction. At once an impulse
to motion is sent out from it to the muscles necessary to move the body
in that direction. In the higher animals these movements are more rapid
and more exact. This is because organs of sense, muscles, nerve-fibres,
and the nerve-cells are all alike highly specialized. In the fish the
sensation is slow, the muscular response sluggish, but the method
remains the same. This is simple reflex action, an impulse from the
environment carried to the brain and then unconsciously reflected back
as motion. The impulse of fear is of the same nature. Reflex action is
in general unconscious, but with animals, as with man, it shades by
degrees into conscious action, and into volition or action "done on
purpose."
=Instinct.=--Different animals show differences in method or degree of
response to external influences. Fishes will pursue their prey, flee
from a threatening motion, or disgorge sand or gravel swallowed with
their food. Such peculiarities of different forms of life constitute
the basis of instinct.
Instinct is automatic obedience to the demands of conditions external
to the nervous system. As these conditions vary with each kind of
animal, so must the demands vary, and from this arises the great
variety actually seen in the instincts of different animals. As the
demands of life become complex, so do the instincts. The greater the
stress of environment, the more perfect the automatism, for impulses to
safe action are necessarily adequate to the duty they have to perform.
If the instinct were inadequate, the species would have become extinct.
The fact that its individuals persist shows that they are provided with
the instincts necessary to that end. Instinct differs from other allied
forms of response to external condition in being hereditary, continuous
from generation to generation. This sufficiently distinguishes it from
reason, but the line between instinct and reason and other forms of
reflex action cannot be sharply drawn.
It is not necessary to consider here the question of the origin of
instincts. Some writers regard them as "inherited habits," while
others, with apparent justice, doubt if mere habits or voluntary
actions repeated till they become a "second nature" ever leave a trace
upon heredity. Such investigators regard instinct as the natural
survival of those methods of automatic response which were most useful
to the life of the animal, the individual having less effective methods
of reflex action perishing, leaving no posterity.
=Classification of Instincts.=--The instincts of fishes may be roughly
classified as to their relation to the individual into egoistic and
altruistic instincts.
_Egoistic instincts_ are those which concern chiefly the individual
animal itself. To this class belong the instincts of feeding, those
of self-defense and of strife, the instincts of play, the climatic
instincts, and environmental instincts, those which direct the animal's
mode of life.
_Altruistic instincts_ are those which relate to parenthood and those
which are concerned with the mass of individuals of the same species.
The latter may be called the social instincts. In the former class, the
instincts of parenthood, may be included the instinct of courtship,
reproduction, home-making, nest-building, and care for the young. Most
of these are feebly developed among fishes.
The instincts of feeding are primitively simple, growing complex
through complex conditions. The fish seizes its prey by direct motion,
but the conditions of life modify this simple action to a very great
degree.
The instinct of self-defense is even more varied in its manifestations.
It may show itself either in the impulse to make war on an intruder
or in the desire to flee from its enemies. Among carnivorous forms
fierceness of demeanor serves at once in attack and in defense.
Herbivorous fishes, as a rule, make little direct resistance to their
enemies, depending rather on swiftness of movement, or in some cases on
simple insignificance. To the latter cause the abundance of minnows,
anchovies, and other small or feeble fishes may be attributed, for all
are the prey of carnivorous fishes, which they far exceed in number.
The instincts of courtship relate chiefly to the male, the female
being more or less passive. Among many fishes the male makes himself
conspicuous in the breeding season, spreading his fins, intensifying
his pigmented colors through muscular tension, all this supposedly to
attract the attention of the female. That this purpose is actually
accomplished by such display is not, however, easily proved. In the
little brooks in spring, male minnows can be found with warts on
the nose or head, with crimson pigment on the fins, or blue pigment
on the back, or jet-black pigment all over the head, or with varied
combination of all these. Their instinct is to display all these to
the best advantage, even though the conspicuous hues lead to their own
destruction.
The movements of many migratory animals are mainly controlled by the
impulse to reproduce. Some pelagic fishes, especially flying fishes
and fishes allied to the mackerel, swim long distances to a region
favorable for a deposition of spawn. Some species are known only in the
waters they make their breeding homes, the individuals being scattered
through the wide seas at other times. Many fresh-water fishes, as
trout, suckers, etc., forsake the large streams in the spring,
ascending the small brooks where they can rear their young in greater
safety. Still others, known as anadromous fishes, feed and mature in
the sea, but ascend the rivers as the impulse of reproduction grows
strong. An account of these is given in a subsequent paragraph.
[Illustration: FIG. 118.--Jaws of _Nemichthys avocetta_. Jordan and
Gilbert.]
=Variability of Instincts.=--When we study instincts of animals with
care and in detail, we find that their regularity is much less than has
been supposed. There is as much variation in regard to instinct among
individuals as there is with regard to other characters of the species.
Some power of choice is found in almost every operation of instinct.
Even the most machine-like instinct shows some degree of adaptability
to new conditions. On the other hand, in no animal does reason show
entire freedom from automatism or reflex action. "The fundamental
identity of instinct with intelligence," says Dr. Charles O. Whitman,
"is shown in their dependence upon the same structural mechanism (the
brain and nerves) and in their responsive adaptability."
=Adaptation to Environment.=--In general food-securing structures
are connected with the mouth, or, as in the anglers, are hung as
lures above it; spines of offense and defense, electric organs,
poison-glands, and the like are used in self-protection; the bright
nuptial colors and adornments of the breeding season are doubtfully
classed as useful in rivalry; the egg-sacs, nests, and other structures
or habits may serve to defend the young, while skinny flaps, sand
or weed-like markings, and many other features of mimicry serve as
concessions to the environment.
Each kind of fishes has its own ways of life, fitted to the conditions
of environment. Some species lie on the bottom, flat, as a flounder,
or prone on their lower fins, as a darter or a stone-roller. Some swim
freely in the depths, others at the surface of the depths. Some leap
out of the water from time to time, as the mullet (_Mugil_) or the
tarpon (_Tarpon atlanticus_).
[Illustration: FIG. 119.--Catalina Flying Fish, _Cypsilurus
californicus_ (Cooper). Santa Barbara.]
=Flight of Fishes.=--Some fishes called the flying-fishes sail through
the air with a grasshopper-like motion that closely imitates true
flight. The long pectoral fins, wing-like in form, cannot, however, be
flapped by the fish, the muscles serving only to expand or fold them.
These fishes live in the open sea or open channel, swimming in large
schools. The small species fly for a few feet only, the large ones for
more than an eighth of a mile. These may rise five to twenty feet above
the water.
The flight of one of the largest flying fishes (_Cypsilurus
californicus_) has been carefully studied by Dr. Charles H. Gilbert and
the writer. The movements of the fish in the water are extremely rapid.
The sole motive power is the action under the water of the strong tail.
No force can be acquired while the fish is in the air. On rising from
the water the movements of the tail are continued until the whole body
is out of the water. When the tail is in motion the pectorals seem in
a state of rapid vibration. This is not produced by muscular action
on the fins themselves. It is the body of the fish which vibrates,
the pectorals projecting farthest having the greatest amplitude of
movement. While the tail is in the water the ventral fins are folded.
When the action of the tail ceases the pectorals and ventrals are
spread out wide and held at rest. They are not used as true wings,
but are held out firmly, acting as parachutes, enabling the body to
skim through the air. When the fish begins to fall the tail touches
the water. As soon as it is in the water it begins its motion, and
the body with the pectorals again begins to vibrate. The fish may, by
skimming the water, regain motion once or twice, but it finally falls
into the water with a splash. While in the air it suggests a large
dragon-fly. The motion is very swift, at first in a straight line,
but is later deflected in a curve, the direction bearing little or no
relation to that of the wind. When a vessel passes through a school of
these fishes, they spring up before it, moving in all directions, as
grasshoppers in a meadow.
[Illustration: FIG. 120.--Sand-darter, _Ammocrypta clara_ (Jordan and
Meek). Des Moines River.]
=Quiescent Fishes.=--Some fishes, as the lancelet, lie buried in
the sand all their lives. Others, as the sand-darter (_Ammocrypta
pellucida_) and the hinalea (_Julis gaimard_), bury themselves in the
sand at intervals or to escape from their enemies. Some live in the
cavities of tunicates or sponges or holothurians or corals or oysters,
often passing their whole lives inside the cavity of one animal. Many
others hide themselves in the interstices of kelp or seaweeds. Some
eels coil themselves in the crevices of rocks or coral masses, striking
at their prey like snakes. Some sea-horses cling by their tails to
gulfweed or sea-wrack. Many little fishes (_Gobiomorus_, _Carangus_,
_Psenes_) cluster under the stinging tentacles of the Portuguese
man-of-war or under ordinary jellyfishes. In the tide-pools, whether
rock, coral, or mud, in all regions multitudes of little fishes abound.
As these localities are neglected by most collectors, they have proved
of late years a most prolific source of new species. The tide-pools of
Cuba, Key West, Cape Flattery, Sitka, Unalaska, Monterey, San Diego,
Mazatlan, Hilo, Kailua and Waiahæ in Hawaii, Apia and Pago-Pago in
Samoa, the present writer has found peculiarly rich in rock-loving
forms. Even richer are the pools of the promontories of Japan, Hakodate
Head, Misaki, Awa, Izu, Waka, and Kagoshima, where a whole new fish
fauna unknown to collectors in markets and sandy bays has been brought
to light. Some of these rockfishes are left buried in the rock weeds
as the tide flows, lying quietly until it returns. Others cling to the
rocks by ventral suckers, while still others depend for their safety on
their powers of leaping or on their quickness of their movements in the
water. Those of the latter class are often brilliantly colored, but the
others mimic closely the algæ or the rocks. Some fishes live in the sea
only, some prefer brackish-water. Some are found only in the rivers,
and a few pass more or less indiscriminately from one kind of water to
another.
[Illustration: FIG. 121.--Pearl-fish, _Fierasfer acus_ (Linnæus),
issuing from a _Holothurian_. Coast of Italy. (After Emery.)]
[Illustration: FIG. 122.--Portuguese Man-of-war Fish, _Gobiomorus
gronovii_. Family _Stromateidæ_].
=Migratory Fishes.=--The movements of migratory fishes are mainly
controlled by the impulse of reproduction. Some pelagic fishes,
especially those of the mackerel and flying-fish families, swim long
distances to a region favorable for the deposition of spawn. Others
pursue for equal distances the schools of menhaden or other fishes
which serve as their prey. Some species are known mainly in the waters
they make their breeding homes, as in Cuba, Southern California,
Hawaii, or Japan, the individuals being scattered at other times
through the wide seas.
=Anadromous Fishes.=--Many fresh-water fishes, as trout and suckers,
forsake the large streams in the spring, ascending the small brooks
where their young can be reared in greater safety. Still others, known
as _anadromous_ fishes, feed and mature in the sea, but ascend the
rivers as the impulse of reproduction grows strong. Among such fishes
are the salmon, shad, alewife, sturgeon, and striped bass in American
waters. The most remarkable case of the anadromous instinct is found in
the king salmon or quinnat (_Oncorhynchus tschawytscha_) of the Pacific
Coast. This great fish spawns in November, at the age of four years and
an average weight of twenty-two pounds. In the Columbia River it begins
running with the spring freshets in March and April. It spends the
whole summer, without feeding, in the ascent of the river. By autumn
the individuals have reached the mountain streams of Idaho, greatly
changed in appearance, discolored, worn, and distorted. The male is
humpbacked, with sunken scales, and greatly enlarged, hooked, bent, or
twisted jaws, with enlarged dog-like teeth. On reaching the spawning
beds, which may be a thousand miles from the sea in the Columbia, over
two thousand in the Yukon, the female deposits her eggs in the gravel
of some shallow brook. The male covers them and scrapes the gravel
over them. The female salmon does as much as the male in covering the
eggs. Then both male and female drift tail foremost helplessly down the
stream; none, so far as certainly known, ever survive the reproductive
act. The same habits are found in the five other species of salmon in
the Pacific, but in most cases the individuals do not start so early
nor run so far. The blue-back salmon or redfish, however, does not fall
far short in these regards. The salmon of the Atlantic has a similar
habit, but the distance traveled is everywhere much less, and most of
the hook-jawed males drop down to the sea and survive to repeat the
acts of reproduction.
[Illustration: FIG. 123.--Tide-pools of Misaki. The Misaki Biological
Station, from the north side.]
_Catadromous_ fishes, as the true eel (_Anguilla_), reverse this order,
feeding in the rivers and brackish estuaries, apparently finding their
usual spawning-ground in the sea.
[Illustration: FIG. 124.--Squaw-fish, _Ptychocheilus oregonensis_
(Richardson). Columbia River.]
=Pugnacity of Fishes.=--Some fishes are very pugnacious, always
ready for a quarrel with their own kind. The sticklebacks show this
disposition, especially the males. In Hawaii the natives take advantage
of this trait to catch the Uu (_Myripristis murdjan_), a bright
crimson-colored fish found in those waters. The species lives in
crevices in lava rocks. Catching a live one, the fishermen suspend it
by a string in front of the rocks. It remains there with spread fins
and flashing scales, and the others come out to fight it, when all are
drawn to the surface by a concealed net. Another decoy is substituted
and the trick is repeated until the showy and quarrelsome fishes are
all secured.
In Siam the fighting-fish (_Betta pugnax_) is widely noted. The
following account of this fish is given by Cantor:[11]
"When the fish is in a state of quiet, its dull colors present nothing
remarkable; but if two be brought together, or if one sees its own
image in a looking-glass, the little creature becomes suddenly excited,
the raised fins and the whole body shine with metallic colors of
dazzling beauty, while the projected gill membrane, waving like a black
frill round the throat, adds something of grotesqueness to the general
appearance. In this state it makes repeated darts at its real or
reflected antagonist. But both, when taken out of each other's sight,
instantly become quiet. The fishes were kept in glasses of water, fed
with larvæ of mosquitoes, and had thus lived for many months. The
Siamese are as infatuated with the combats of these fish as the Malays
are with their cock-fights, and stake on the issue considerable sums,
and sometimes their own persons and families. The license to exhibit
fish-fights is farmed, and brings a considerable annual revenue to
the king of Siam. The species abounds in the rivulets at the foot
of the hills of Penang. The inhabitants name it 'Pla-kat,' or the
'fighting-fish'; but the kind kept especially for fighting is an
artificial variety cultivated for the purpose."
A related species is the equally famous tree-climber of India (_Anabas
scandens_). In 1797 Lieutenant Daldorf describes his capture of an
_Anabas_, five feet above the water, on the bark of a palm-tree. In the
effort to do this, the fish held on to the bark by its preopercular
spines, bent its tail, inserted its anal spines, then pushing forward,
repeated the operation.
=Fear and Anger in Fishes.=--From an interesting paper by Surgeon
Francis Day[12] on Fear and Anger in Fishes we may make the following
extracts, slightly condensed and with a few slight corrections in
nomenclature. The paper is written in amplification of another by Rev.
S. J. Whitmee, describing the behavior of aquarium fishes in Samoa.
[Illustration: FIG. 125.--Squaw-fish, _Ptychocheilus grandis_ Agassiz.
Running up a stream to spawn, the high water, after a rain, falling,
leaves the fishes stranded. Kelsey Creek, Clear Lake, California, April
29, 1899. (Photograph by O. E. Meddaugh.)--Page 164.]
The means of expression in animals adverted to by Mr. Darwin (excluding
those of the ears, which would be out of place in fishes) are: sounds,
vocally or otherwise produced; the erection of dermal appendages under
the influence of anger or terror, which last would be analogous to
the erection of scales and fin-rays among fishes. Regarding special
expressions, as those of joy, pain, astonishment, etc., we could
hardly expect such so well marked in fishes as in some of the higher
animals, in which the play of the features often affords us an insight
into their internal emotions. Eyes[13] destitute of movable eyelids,
cheeks covered with scales, or the head enveloped in dermal plates, can
scarcely mantle into a smile or expand into a broad grin. We possess,
however, one very distinct expression in fishes which is absent or but
slightly developed in most of the higher animals, namely, change of
color. All are aware that when a fish sickens, its brilliant colors
fade, but less so how its color may be augmented by anger, and a loss
of it be occasioned by depression, the result of being vanquished by a
foe. Some forms also emit sounds when actuated by terror, and perhaps
in times of anger; but of this last I possess no decided proofs.
Similar to the expression of anger in _Betta_ is that of the
three-spined stickleback (_Gasterosteus aculeatus_).[14] After a fight
between two examples, according to Couch, "a strange alteration takes
place almost immediately in the defeated party: his gallant bearing
forsakes him; his gay colors fade away; he becomes again speckled and
ugly; and he hides his disgrace amongst his peaceable companions who
occupy together that part of the tub which their tyrants have not taken
possession of; he is, moreover, for some time the constant object of
his conqueror's persecution."
Fear is shown by fish in many ways. There is not an angler unacquainted
with the natural timidity of fishes, nor a keeper in charge of a
salmon-pass, who does not know how easy it is for poachers to deter the
salmon from venturing along the path raised expressly for his use.
Among the coral reefs of the Andaman Islands I found the little
_Chromis lepisurus_ abundant. As soon as the water was splashed
they appeared to retire for safety to the branching coral, where no
large fish could follow them; so frightened did they become that on
an Andamanese diving from the side of the boat, they at once sought
shelter in the coral, in which they remained until it was removed
from the sea. In Burma I observed, in 1869, that when weirs are not
allowed to stretch across the rivers (which would impede navigation),
the open side as far as the bank is studded with reeds; these, as the
water passes over them, cause vibration, and occasion a curious sound
alarming the fishes, which, crossing to the weired side of the river,
become captured.
Hooker, alluding to gulls, terns, wild geese, and pelicans in the
Ganges Valley, observes: "These birds congregate by the sides of pools
and beat the water with violence, so as to scare the fish, which then
become an easy prey--a fact which was, I believe, first indicated by
Pallas during his residence on the banks of the Caspian Sea."[15]
Fishes, under the influence of terror, dash about with their fins
expanded, and often run into places which must destroy them. Thus
droves and droves of sardines in the east, impelled by the terror
of pursuing sharks, bonitos, and other voracious fishes, frequently
throw themselves on the shores in enormous quantities. Friar Odoric,
who visited Ceylon about 1320, says: "There are fishes in those seas
which come swimming towards the said country in such abundance, that
for a great distance into the sea nothing can be seen but the backs
of fishes, which, casting themselves on the shore, do suffer men for
the space of three days to come, and to take as many of them as they
please, and then they return again into the sea."[16]
Pennant tells us that the river bullhead (_Cottus gobio_) "deposits
its spawn in a hole it forms in the gravel, and quits it with great
reluctance." General Hardwicke tells how the gouramy (_Osphromenus
gouramy_), in the Mauritius, forms a nest amongst the herbage growing
in the shallow water in the sides of tanks. Here the parent continues
to watch the place with the greatest vigilance, driving away any
interloping fish. The amphibious walking-fish of Mysore (_Ophiocephalus
striatus_) appears to make a nest very similar to that of the gouramy,
and over it the male keeps guard; but should he be killed or captured,
the vacant post is filled by his partner. (Colonel Puckle.) When very
young the fishes keep with and are defended by their parents, but so
soon as they are sufficiently strong to capture prey for themselves
they are driven away to seek their own subsistence. (See Fishes of
India, p. 362.) But it is not only these monogamous amphibious fishes
which show an affection for their eggs and also for their fry, but even
the little _Etroplus maculatus_ has been observed to be equally fond of
its ova. "The eggs are not very numerous and are deposited in the mud
at the bottom of the stream, and, when hatched, both parents guard the
young for many days, vigorously attacking any large fish that passes
near them."[17]
Although the proceedings of the members of the marine and estuary genus
of sea-cat (_Tachysurus_) and its allies show not quite so distinctly
signs of affection, still it must be a well-developed instinct which
induces the male to carry about the eggs in its mouth until hatched,
and to remove them in this manner when danger is imminent. I have taken
the ova just ready for the young to come forth out of the mouth and
fauces of the parent (male) fish; and in every animal dissected there
was no trace of food in the intestinal tract.
=Calling the Fishes.=--At many temples in India fishes are called to
receive food by means of ringing bells or musical sounds. Carew, in
Cornwall, is said to have called the gray mullet together by making a
noise like chopping with a cleaver. Lacépède relates that some fishes,
which had been kept in the basins out of the Tuileries for more than a
century, would come when called by their names, and that in many parts
of Germany trout, carp, and tench are summoned to their food by the
sound of a bell. These instances are mostly due to the fishes having
learned by experience that on the hearing certain sounds they may
expect food. But Lacépède mentions that some were able to distinguish
their individual names; and the same occurs in India. Lieutenant
Connolly[18] remarked upon seeing numerous fishes coming to the ghaut
at Sidhnath to be fed when called; and on "expressing our admiration
of the size of the fish, 'Wait,' said a bystander, 'until you have
seen Raghu.' The Brahmin called out his name in a peculiar tone of
voice; but he would not hear. I threw in handful after handful of
ottah (flour) with the same success, and was just leaving the ghaut,
despairing and doubting, when a loud plunge startled me. I thought
somebody had jumped off the bastion of the ghaut into the river, but
was soon undeceived by the general shout of 'Raghu, raghu,' and by
the fishes, large and small, darting away in every direction. Raghu
made two or three plunges, but was so quick in his motions that I was
unable to guess at his species." [It may be said in relation to these
stories quoted by Dr. Day, that they probably belong to the mythology
of fishes. It is very doubtful if fishes are able to make any such
discrimination among sounds in the air.]
=Sounds of Fishes.=--Pallegoix states that in Siam the dog's-tongue
(_Cynoglossus_) is a kind of sole; it attaches itself to the bottom of
boats, and makes a sonorous noise, which is more musical when several
are stuck to the same boat and act in concert (vol. i. p. 193). These
noises can scarcely be due to anger or fear. Sir J. Bowring (vol. ii.
p. 276) also remarks upon having heard this fish, "which sticks to the
bottoms of the boats, and produces a sound something like that of a
jew's-harp struck slowly, though sometimes it increases in loudness,
so as to resemble the full tones and sound of an organ. My men have
pointed me out a fish about four inches long as the author of the
music."
Some years since, at Madras, I (Dr. Day) obtained several specimens
of a fresh-water Siluroid fish (_Macrones vittatus_) which is termed
the "fiddler" in Mysore. I touched one which was on the wet ground, at
which it appeared to become very irate, erecting its dorsal fin, making
a noise resembling the buzzing of a bee. Having put some small carp
into an aquarium containing one of these fishes, it rushed at a small
example, _seized it by the middle of its back_, and shook it like a dog
killing a rat; at this time its barbels were stiffened out laterally
like a cat's whiskers.
Many fish when captured make noises, perhaps due to terror. Thus the
_Carangus hippos_, _Tetraodon_, and others grunt like a hog. Darwin
(Nat. Journ., vol. vii) remarks on a catfish found in the Rio Paraná,
and called the armado, which is remarkable for a harsh grating noise
when caught by hook and line; this noise can be distinctly heard when
the fish is beneath the water.
The cuckoo-gurnard (_Trigla pini_) and the maigre (_Pseudosciæna
aquila_) utter sounds when taken out of the water; and herrings,
when the net has been drawn over them, have been observed to do the
same: "this effect has been attributed to an escape of air from the
air-bladder; but no air-bladder exists in the _Cottus_, which makes a
similar noise."
The lesser weaver (_Trachinus_) buries itself in the loose soil at the
bottom of the water, leaving only its head exposed, and awaits its
prey. If touched, it strikes upwards or sideways; and Pennant says it
directs its blows with as much judgment as a fighting-cock. (Yarrell,
vol. i. p. 26.) Fishermen assert that wounds from its anterior dorsal
spines are more venomous than those caused by the spines on its
gill-covers.
As regards fighting, I should suppose that, unless some portion of the
body is peculiarly adapted for this purpose, as the rostrum of the
swordfish, or the spine on the side of the tail in the lancet-fishes,
we must look chiefly to the armature or covering of the jaws for
weapons of offense.
=Lurking Fishes.=--Mr. Whitmee supposes that most carnivorous fish
capture their prey by outswimming them; but to this there are numerous
exceptions; the angler or fishing-frog (_Lophis piscatorius_), "while
crouching close to the ground, by the action of its ventral and
pectoral fins stirs up the sand and mud; hidden by the obscurity thus
produced, it elevates its anterior dorsal spines, moves them in various
directions by way of attraction as a bait, and the small fishes,
approaching either to examine or to seize them, immediately become the
prey of the fisher." (Yarrell.) In India we find a fresh-water Siluroid
(_Chaca lophioides_) which "conceals itself among the mud, from which,
by its lurid appearance and a number of loose filamentous substances
on its skin, it is scarcely distinguishable; and with an immense open
mouth it is ready to seize any small prey that is passing along." (Ham.
Buchanan.) In March, 1868, I obtained a fine example of _Ichthyscopus
lebeck_ (Fishes of India, p. 261), which I placed in water having a bed
of mud; into this it rapidly worked itself, first depressing one side
and then another, until only the top of its head and mouth remained
above the mud, whilst a constant current was kept up through its gills.
It made a noise, half snapping and half croaking, when removed from its
native element.
In the Royal Westminster Aquarium, says Dr. Day, is a live example
of the electric eel (_Electrophorus electricus_) which has in its
electric organs the means of showing when it is affected by anger or
terror. Some consider this curious property is for protection against
alligators: it is certainly used against fishes for the purpose of
obtaining food; but when we remember how, when the Indians drive in
horses and mules to the waters infested by the eels, they immediately
attack them, we must admit that such cannot be for the purpose of
preying upon them, but is due to anger or terror at being disturbed.
(DAY.)
=Carrying Eggs in the Mouth.=--Many catfishes (_Siluridæ_) carry their
eggs in the mouth until hatched. The first and most complete account
of this habit of catfishes is that by Dr. Jeffries Wyman, which he
communicated to the Boston Society of Natural History at its meeting on
September 15, 1857. In 1859, in a paper entitled "On Some Unusual Modes
of Gestation," Dr. Wyman published a full account of his observations
as follows, here quoted from a paper on Surinam fishes by Evermann and
Goldsborough:
"Among the Siluroid fishes of Guiana there are several species which,
at certain seasons of the year, have their mouths and branchial
cavities filled either with eggs or young, and, as is believed, for the
purpose of incubation. My attention was first called to this singular
habit by the late Dr. Francis W. Cragin, formerly United States consul
at Paramaribo, Surinam. In a letter dated August, 1854, he says:
"'The eggs you will receive are from another fish. The different
fishermen have repeatedly assured me that these eggs in their nearly
mature state are carried in the mouths of the parent till the young are
relieved by the bursting of the sac. Do you either know or believe this
to be so, and, if possible, where are the eggs conceived and how do
they get into the mouth?'
"In the month of April, 1857, on visiting the market of Paramaribo, I
found that this statement, which at first seemed to be very improbable,
was correct as to the existence of eggs in the mouths of several
species of fish. In a tray of fish which a negro woman offered for
sale, I found the mouths of several filled with either eggs or young,
and subsequently an abundance of opportunities occurred for repeating
the observation. The kinds most commonly known to the colonists,
especially to the negroes, are _jara-bakka_, _njinge-njinge_, _koepra_,
_makrede_, and one or two others, all belonging either to the genus
_Bagrus_ or one nearly allied to it. The first two are quite common in
the market, and I have seen many specimens of them; for the last two I
have the authority of negro fishermen, but have never seen them myself.
The eggs in my collection are of three different sizes, indicating so
many species, one of the three having been brought to me without the
fish from which they were taken.
"The eggs become quite large before they leave the ovaries, and are
arranged in three zones corresponding to three successive broods, and
probably to be discharged in three successive years; the mature eggs
of a jara-bakka 18 inches long measure three-fourths of an inch in
diameter; those of the second zone, one-fourth; and those of the third
are very minute, about one-sixteenth of an inch.
"A careful examination of eight specimens of njinge-njinge about 9
inches long gave the following results:
"The eggs in all instances were carried in the mouths of the males.
This protection, or gestation of the eggs by the males, corresponds
with what has been long noticed with regard to other fishes, as, for
example, _Syngnathus_, where the marsupial pouch for the eggs or
young is found in the males only, and _Gasterosteus_, where the male
constructs the nest and protects the eggs during incubation from the
voracity of the females.
"In some individuals the eggs had been recently laid, in others they
were hatched and the foetus had grown at the expense of some other food
than that derived from the yolk, as this last was not proportionally
diminished in size, and the foetus weighed more than the undeveloped
egg. The number of eggs contained in the mouth was between twenty
and thirty. The mouth and branchial cavity were very much distended,
rounding out and distorting the whole hyoid and branchiostegal region.
Some of the eggs even partially protruded from the mouth. The ova were
not bruised or torn as if they had been bitten or forcibly held by the
teeth. In many instances the foetuses were still alive, though the
parent had been dead for many hours.
"No young or eggs were found in the stomach, although the mouth was
crammed to its fullest capacity.
"The above observations apply to njinge-njinge. With regard to
jarra-bakka, I had but few opportunities for dissection, but in several
instances the same conditions of the eggs were noticed as stated above;
and in one instance, besides some nearly mature foetuses contained in
the mouth, two or three were squeezed apparently from the stomach,
but not bearing any marks of violence or of the action of the gastric
fluid. It is probable that these found their way into that last cavity
after death, in consequence of the relaxation of the sphincter which
separates the cavities of the mouth and the stomach. These facts lead
to the conclusion that this is a mouth gestation, as the eggs are found
there in all stages of development, and even for some time after they
are hatched.
"The question will be very naturally asked, how under such
circumstances these fishes are able to secure and swallow their food. I
have made no observations bearing upon such a question. Unless the food
consists of very minute particles it would seem necessary that during
the time of feeding the eggs should be disgorged. If this supposition
be correct, it would give a very probable explanation of the only fact
which might be considered at variance with the conclusion stated above,
viz., that we have in these fishes a mouth gestation. In the mass
of eggs with which the mouth is filled I have occasionally found the
eggs, rarely more than one or two, of another species. The only way in
which their presence may be accounted for, it seems to me, is by the
supposition that while feeding the eggs are disgorged, and as these
fishes are gregarious in their habits, when the ova are recovered the
stray eggs of another species may be introduced into the mouth among
those which naturally belong there."
One of the earliest accounts of this curious habit which we have seen
is that by Dr. Günther, referring to specimens of _Tachysurus fissus_
from Cayenne received from Prof. R. Owen:
"These specimens having had the cavity of the mouth and of the gills
extended in an extraordinary manner, I was induced to examine the cause
of it, when, to my great surprise, I found them filled with about
twenty eggs, rather larger than an ordinary pea, perfectly uninjured,
and with the embryos in a forward state of development. The specimens
are males, from 6 to 7 inches long, and in each the stomach was almost
empty.
"Although the eggs might have been put into the mouth of the fish by
their captor, this does not appear probable. On the other hand, it
is a well-known fact that the American Siluroids take care of their
progeny in various ways; and I have no doubt that in this species and
in its allies the males carry the eggs in their mouths, depositing them
in places of safety and removing them when they fear the approach of
danger or disturbance."
=The Unsymmetrical Eyes of Flounders.=--In the two great families of
flounders and soles the head is unsymmetrically formed, the cranium
being twisted and both eyes placed on the same side. The body is
strongly compressed, and the side possessing the eyes is uppermost in
all the actions of the fish. This upper side, whether right or left, is
colored, while the eyeless side is white or very nearly so.
It is well known that in the very young flounder the body rests
upright in the water. After a little there is a tendency to turn to
one side and the lower eye begins its migration to the other side, the
interorbital bones or part of them moving before it. In most flounders
the eye seems to move over the surface of the head, before the dorsal
fin, or across the axil of its first ray. In the tropical genus
_Platophrys_ the movement of the eye is most easily followed, as the
species reach a larger size than do most flounders before the change
takes place. The larva, while symmetrical, is in all cases transparent.
[Illustration: FIG. 126.]
[Illustration: FIG. 127.
FIGS. 126, 127.--Larval stages of _Platophrys podas_, a flounder of the
Mediterranean, showing the migration of the eye. (After Emery.)]
In a recent study of the migration of the eye in the winter flounder
(_Pseudopleuronectes americanus_) Mr. Stephen R. Williams reaches the
following conclusions:
1. The young of _Limanda ferruginea_ (the rusty dab) are probably in
the larval stage at the same time as those of _Pseudopleuronectes
americanus_ (the winter flounder).
2. The recently hatched fish are symmetrical, except for the relative
positions of the two optic nerves.
3. The first observed occurrence in preparation for metamorphosis in
_P. americanus_ is the rapid resorption of the part of the supraorbital
cartilage bar which lies in the path of the eye.
4. Correlated with this is an increase in distance between the eyes
and the brain, caused by the growth of the facial cartilages.
5. The migrating eye moves through an arc of about 120 degrees.
[Illustration: FIG. 128.--_Platophrys lunatus_ (Linnæus), the Wide-eyed
Flounder. Family _Pleuronectidæ_. Cuba. (From nature by Mrs. H. C.
Nash.)]
6. The greater part of this rotation (three-fourths of it in _P.
americanus_) is a rapid process, taking not more than three days.
7. The anterior ethmoidal region is not so strongly influenced by the
twisting as the ocular region.
[Illustration: FIG. 129.--Young Flounder, just hatched, with
symmetrical eyes. (After S. R. Williams.)]
8. The location of the olfactory nerves (in the adult) shows that the
morphological midline follows the interorbital septum.
9. The cartilage mass lying in the front part of the orbit of the adult
eye is a separate anterior structure in the larva.
10. With unimportant differences, the process of metamorphosis in the
sinistral fish is parallel to that in the dextral fish.
11. The original location of the eye is indicated in the adult by the
direction first taken, as they leave the brain, by those cranial nerves
having to do with the transposed eye.
12. The only well-marked asymmetry in the adult brain is due to the
much larger size of the olfactory nerve and lobe of the ocular side.
13. There is a perfect chiasma.
14. The optic nerve of the migrating eye is always anterior to that of
the other eye.
[Illustration: FIG. 130.--Larval Flounder, _Pseudopleuronectes
americanus_. (After S. R. Williams.)]
[Illustration: FIG. 131.--Larval Flounder, _Pseudopleuronectes
americanus_. (After S. R. Williams.)]
"The why of the peculiar metamorphosis of the _Pleuronectidæ_ is an
unsolved problem. The presence or absence of a swim-bladder can have
nothing to do with the change of habit of the young flatfish, for _P.
americanus_ must lose its air-bladder before metamorphosis begins,
since sections showed no evidence of it, whereas in _Lophopsetta
maculata_, 'the windowpane flounder,' the air-sac can often be seen
by the naked eye up to the time when the fish assumes the adult
coloration, and long after it has assumed the adult form.
"Cunningham has suggested that the weight of the fish acting upon the
lower eye after the turning would press it toward the upper side out
of the way. But in all probability the planktonic larva rests on the
sea-bottom little if at all before metamorphosing. Those taken by Mr.
Williams into the laboratory showed in resting no preference for either
side until the eye was near the midline.
"The fact that the change in all fishes is repeated during the
development of each individual fish has been used to support the
proposition that the flatfishes as a family are a comparatively recent
product. They are, on the other hand, comparatively ancient. According
to Zittel flatfishes of species referable to genera living at present,
_Rhombus_ (_Bothus_) and _Solea_, are found in the Eocene deposits.
These two genera are notable in that _Bothus_ is one of the least and
_Solea_ the most unsymmetrical of the _Pleuronectidæ_.
[Illustration: FIG. 132.--Face view of recently hatched Flounder.
(After S. R. Williams.)]
"The degree of asymmetry can be correlated with the habit of the
animal. Those fishes, such as the sole and shore-dwelling flounders,
which keep to the bottom are the most twisted representatives of the
family, while the more freely swimming forms, like the sand-dab, summer
flounder, and halibut, are more nearly symmetrical. Asymmetry must be
of more advantage to those fishes which grub in the mud for their food
than to those which capture other fishes; of the latter those which
move with the greatest freedom are the most symmetrical.
"This deviation from the bilateral condition must have come about
either as a 'sport' or by gradual modification of the adults. If by the
latter method--the change proving to be advantageous--selection favored
its appearing earlier and earlier in ontogeny, until it occurred in the
stages of planktonic life. Metamorphosis at a stage earlier than this
would be a distinct disadvantage, because of the lack of the customary
planktonic food at the sea-bottom. At present some forms of selection
are probably continually at work fixing the limit of the period of
metamorphosis by the removal of those individuals which attempt the
transformation at unsuitable epochs; for instance, at the time of
hatching. That there are such individuals is shown by Fullarton, who
figures a fish just hatched 'anticipating the twisting and subsequent
unequal development exhibited by the head of Pleuronectids.' Those
larvæ which remain pelagic until better able to compete at the
sea-bottom become the adults which fix the time of metamorphosis on
their progeny." (S. R. WILLIAMS.)
So far as known to the writer, the metamorphosis of flounders always
occurs while the individual is still translucent and swimming at the
surface of the sea before sinking to the bottom.
FOOTNOTES:
[11] Cantor, Catal. Malayan Fishes, 1850, p. 87. Bowring, Siam, p. 155,
gives a similar account of the battles of these fishes.
[12] Francis Day, on Fear and Anger in Fishes, Proc. Zool. Society,
London, Feb. 19, 1878, pp. 214-221.
[13] Couch (Illustrations, etc., p. 305) says: "The faculty of giving
forth brilliant light from the eyes is said to have been observed by
fishermen in the blue shark, as in a cat."
[14] Couch, "British Fishes," 1865, vol. iv. p. 172.
[15] Himalayan Journals, vol. i. p. 80.
[16] Hakluyt, vol. ii. p. 37.
[17] Jerdon, "Madras Journal of Literature and Science," 1849, p. 143.
[18] "Observations on the Past and Present Condition of Onjein,"
Journal of the Asiatic Society of Bengal, vi, p. 820.