may well ask why the possession of electric power, the most strange, and
until recently the most inexplicable, attribute of any of the
inhabitants of the water, does not play a greater part in the marvellous
narratives of ancient voyages? The _remora_, or sucking-fish, magnified
a thousand times in imaginations excited by a world of strange and new
experience, was the besetting foe of mariners in Northern waters.
Clinging to the keel, it kept their barques for weeks in the _mare
pigrum_, the sluggish sea of drifting ice. Whales, rising like sandbanks
above the waves, tempted the weary crews to make fast to their
treacherous bulk, and then plunged to the bottom, carrying with them
both ships and sailors. Gigantic squids thrust their slimy arms down the
hatchways, and plucked sleeping seamen from their berths and strangled
them before their comrades’ eyes. But the “torpedo”—the paralyzer—though
as well known then to the fishers of the Mediterranean as it is now
known, under the name of the “crampfish,” or electric ray, to the
trawlers of Cornwall or the Channel, seems to have appealed less to the
fancies of the sailors of old, than the new though less mysterious
powers of the monsters, great and small, which rushed beneath their
keels in hyperborean seas. Possibly the powers of the “torpedo” were too
well known to excite curiosity, though it is difficult to believe that a
creature which sometimes reaches a bulk of 100 lbs. weight, and can emit
an electrical discharge strong enough to kill a duck, or to cause in the
human arm a “creeping sensation felt in the whole limb up to the
shoulder, accompanied by a violent trembling, and sharp pain in the
elbow,” followed by loss of sensation for an hour, was not as suggestive
to sailors’ fancies as the tentacles of the cuttle-fish, or the
sucking-discs of the _remora_. But if the fabulous terrors of the last
were enough to deter the boldest mariners who sailed beyond Thule, it is
matter for congratulation that early explorers were unacquainted with
the powers and proportions of a monster of still more formidable mould,
the electric eel of Southern America. Its mere aspect is lurid, sombre,
and repulsive. Its belly glows like red-hot iron, as if fresh from the
lake of living fire. Its back is dark and shiny, as if tinged by inky
Cocytus. Around its lips and jaws are glowing spots like bubbles of hot
metal. The colours meet in a line along the side; and the creature, when
drawn from the water, looks as though formed of two welded portions of
iron, the one hot, the other cold, just plunged into the blacksmith’s
cistern. Small eyes, blue and bleared, are set in the top of a blunt
ferocious head, from which the strong and muscular body tapers gradually
to a point at the tail. Such, at least, is the appearance of the two
electric eels at the Zoo, of whose power the writer, with curiosity
stimulated by Baron Humboldt’s unique description of these creatures in
the inland pools of tropical America, recently made trial. Neither the
size of the fish, nor their physical condition in the small tank in
which they exist at present, could reasonably be expected to produce
such results as the great traveller witnessed in the stagnant pools of
the llanos of Caraccas, when the Indians drove a herd of horses into the
water to face the electric discharges of the fish. “These yellowish
livid eels,” he writes, “resembling large aquatic snakes, swim near the
surface of the water, and crowd under the bellies of the horses and
mules. The struggle between animals of so different an organization
affords a very interesting sight. The Indians, armed with harpoons and
long slender reeds, closely surround the pool, and by their wild shouts
and long reeds prevent the horses from coming to the bank. The eels seek
to defend themselves by repeated discharges of their electric batteries,
and for a long time it seems as if theirs would be the victory. Several
horses sink under the violence of the invisible blows which they receive
in the most vital parts, and, benumbed by the force and frequency of the
shocks, disappear beneath the surface. Others, with mane erect and
haggard eyes, raise themselves and endeavour to escape, but are driven
back by the Indians. Within five minutes a couple of horses are killed.
The eel, which is five feet long, presses its body against the belly of
the horse, and attacks at once the heart, the viscera, and the group of
abdominal nerves. It is natural,” the author adds, “that the effect
which a horse experiences should be more powerful than that produced by
the same fish on man, when it touches him only at one of the
extremities. The horses are probably not killed, but stunned, and are
drowned amid the confusion of the struggle between the other horses and
eels.”
The truth of Humboldt’s account of the taking of the electric eels is
sometimes doubted. But apart from the credit due to the deliberate
utterances of one of the greatest minds of modern days, the accuracy of
whose views, even when he put them forward as mere probable surmise, is
being constantly verified by later experience, the powers of the
creatures, even of the small specimen brought to this country, are so
astonishing as to make Humboldt’s account not err on the side of the
marvellous.
It would be difficult, unless the opportunity existed of taking a plunge
into a tank large enough to swim in, and well stocked with electric
eels, to realize by personal experience the precise effect of the shocks
upon the horses; but a record of the writer’s sensations when in
personal contact with these uncanny creatures may perhaps give some
notion of the strength of their electric power. The largest of the pair
in Regent’s Park, about 4½ ft. in length, thick and deep, and probably
weighing from 16 lbs. to 18 lbs., was moving sluggishly on the bottom of
the tank, and was slowly raised to the surface by a landing-net. As its
side became visible, its resemblance to a “cooling cast” was even closer
than when seen from above. When grasped in the middle of the back, there
was just time to realize that it had none of the “lubricity” of the
common eel, when the first shock passed up the arm with a “flicker”
identical with that which a zig-zag flash of lightning leaves upon the
eye, and, as it seemed, with equal speed. A second and third felt like a
blow on the “funny-bone,” and the hand and arm were involuntarily thrown
back with a jerk which flung the water backwards on the pavement and
over the keeper who was kindly assisting in the enterprise. This slight
mishap recalled a far less agreeable result of a shock inflicted on a
previous inquirer, whose recoiling hand had struck the assistant a
severe blow in the face. Unwilling to be baffled by a fish less in size
than the salmon which form the common stock of a fishmonger’s window,
the writer once more endeavoured to hold the eel at any cost of personal
suffering. But the electric powers were too subtle and pervading to be
denied. The first muscular quiver of the fish was resisted; but at the
second, the sense of vibration set up became intolerable, and the
enforced release was as rapid and uncontrollable as the first. The
smaller eel was neither so vigorous nor so resentful as its fellow. But
though the first and second shocks did not compel the grasp to relax, a
third was equally intolerable with that given by the larger fish. The
electrical power seems to increase rapidly in the heavier eels. One of 5
ft. in length, which appeared to be nearly dead when it arrived at the
Gardens, and was therefore handled without ceremony, inflicted a shock
which, as the keeper stated, “nearly sent him on his back;” and the same
fish, when being carried by hand in a tub up to the rooms of the Royal
Society, sent a shock through the water which nearly caused the downfall
of fish and bucket alike. This power of projecting its electric
discharge, either through the water or by means of any conductor, to the
object which it desires to paralyze, may be well observed at the Zoo.
The usual way in which the shocks are received is by grasping a
copper-rod, which is placed in contact with the fish’s back. But it is
when in pursuit of the small fish which form its food that the “range”
of the eel’s battery is best seen. On the last occasion on which the
writer was present at the eel’s feeding-hour, eight or ten lively
gudgeon were taken from a pail, and placed in the eel’s tank. The small
fish at once dived to the bottom, as is their habit, and sought refuge
in the corners, or at the angle made by the meeting of the base and
sides of the stone cistern. Every one of the fish was killed by electric
shock before being eaten; but in the case of those in the corners, it
was impossible for the fish to bring the electric organ, which lies on
each side of the lower part of the tail, into direct contact. The eel,
therefore, swam past them, like a torpedo-boat which intends to
discharge its broadside torpedoes, and as the battery came opposite, the
fish gave a slight quiver, which instantaneously produced a violent
shock in the gudgeon, and turned it belly upwards. After three had been
killed and eaten, the shocks became weaker, and the other gudgeon seemed
only partly paralyzed by the first shock, and sometimes recovered and
swam away in a crippled condition until benumbed by a second shock. One
fish which was “shocked” and left for dead while the eel went in pursuit
of more, recovered after a few minutes, and was subsequently pursued,
received a direct shock from the eel’s side, and was killed. The
inference suggested by the writer’s own experience of the violence of
the shocks inflicted, though with different degrees of intensity, is
that the eel controls the power of the electrical discharge at will,
just as it controls any other function which has its initiative in
muscular action; and that the gudgeons received enough, and no more,
than was sufficient to paralyze them, and make them easy victims for the
slow-moving eel.
------------------------------------------------------------------------
DEEP-SEA LAMPS.
THE possibility of exhibiting the powers of electrical fishes in the
tanks at the Zoo, suggests the question whether, in the progress of
marine aquariums, we shall ever see the luminous creatures of the deep
seas exhibited alive before air-breathing mortals in this upper world.
Virgil’s Sybil set the depth of Tartarus at twice the skyward gaze to
the summit of Olympus. But the profundity of the ocean abyss is such
that in the deep Atlantic Olympus might be imposed upon itself, and Ossa
piled above, without rising to break the surface. The imagination almost
refuses to grasp the physical conditions in an abyss so profound as the
ocean bed off the coast of Porto Rico, wrapped, by a weight of waters
five miles deep, in perpetual darkness and everlasting cold, and under a
pressure of which figures can convey no practical conception. Even at
the average depth of 2,500 fathoms sunlight can never penetrate. The
temperature is only a few degrees above freezing-point, the water is
without movement, there is no plant-life, and the pressure is two and a
half tons on the square inch, or about twenty-five times greater than
that which drives a railway train. Yet it is now certain that where the
fancy painted a survival of the sterile and lifeless plains of an
unformed world, or at most the rude survivals of primitive fossils, the
bed of the deep sea teems with animal life, and the clinging darkness of
its waters is peopled by myriads of fragile and fantastic forms, and
lighted into a blaze by the effulgence from their bodies. Hard as it is
to conceive the bare existence of life under the conditions of the ocean
abyss, the mind pauses in astonishment at the completeness of the
triumph by which creatures apparently doomed to live in eternal night
are supplied not with mere slimy secretions of luminosity, but with rows
of bright and ever-burning lamps, in organs fitted with lenses and
reflectors, which shoot their beams sidelong through the circumfluent
ocean, or project shafts of light before their eyes to illuminate their
path.
The results of recent deep-sea exploration have been summarized by Mr.
Sydney J. Hickson, Fellow of Downing College, Cambridge, in a short work
on _The Fauna of the Deep Sea_, published in the “Modern Science
Series.”[1] Though the bulk and specialized character of the reports of
separate expeditions organized by the English, French, German, Italian,
and Norwegian governments, makes such a task one of no ordinary
difficulty, Mr. Hickson has succeeded in his wish to “give in a small
compass the more important facts of this great mass of literature in
such a form as may interest those who do not possess a specialist’s
knowledge.” The main conclusions are clearly presented with examples and
excellent illustrations, in number sufficient to convince without
bewildering. On one point we could desire a little more information.
There is no suggestion of the means by which creatures differing so
little in bodily frame and tissue from the shallow-water species, from
which they are apparently derived by migration into the deeps, support
the enormous pressure in their present home. Some explanation seems to
be required, though an incident in the recent erection of the Forth
Bridge seems to suggest that the modification of tissue to endure high
pressure may be acquired more rapidly than is supposed. The men employed
in the steel shells or caissons sunk to form the foundations of the
piers, worked in a pressure of air rather greater than the pressure of
the water outside, which would otherwise have penetrated between the
rims of the caissons and the ground. On those days on which they were
not employed, and came to the surface, they felt such pain in the joints
from the expansion of the air, which had been absorbed at high pressure,
that they begged to be allowed to go down into the caissons and spend
their off hours in the pressure to which they had grown accustomed. This
instance of partial migration into conditions of high pressure, seems
worthy of a place among the facts of deep-sea exploration. Yet it must
remain among the strangest features of life in the ocean abyss, that its
inhabitants show so little visible change of structure to meet what
seems the first and most overwhelming change of physical conditions. The
angler-fish and eels, crabs and prawns, star-fish and zoophytes of the
shallow waters are represented in the abyss by forms almost similar in
structure, though that some difference must exist is shown by the fact
that when brought up by the dredge from the depths of the ocean they are
killed and distorted by the diminution and disappearance of the vast
pressure in which they habitually live. “The fish which live at these
enormous depths,” writes Mr. Hickson, “are liable to a curious form of
accident. If, in chasing their prey, or for any other reason, they rise
to a considerable distance above the floor of the ocean, the gases of
their swimming-bladder become greatly expanded, and their specific
gravity reduced. If the muscles are not strong enough to drive the body
downwards, the fish, becoming more and more distended as it goes, is
gradually killed on its long and involuntary journey to the surface of
the sea. The deep-sea fish, then, are exposed to a danger that no other
animals in this world are subject to—namely, that of tumbling upwards.”
Footnote 1:
_The Fauna of the Deep Sea_, by Sydney J. Hickson, M.A., D.Sc. London:
Kegan Paul and Co.
But however obscure the structure which enables the deep-sea creatures
to withstand the pressure of the waters, the means by which they combat
the plague of darkness is evident and astounding. It is well known that
the number of phosphorescent animals, even in shallow tropical seas, is
such that they can illuminate not only the waters, but the air, to a
considerable distance. Sir Wyville Thompson states, that near the Cape
Verde Islands he saw the sea in such a blaze of phosphorescence that,
though there was no moon, “it was easy to read the smallest print,
sitting at the after-port in the cabin; while the bows shed, on either
side, rapidly widening wedges of radiance, so vivid as to throw the
sails and riggings into distinct lights and shadows.” But, great as is
the number of luminous creatures in the shallow waters, the percentage
among those dredged from the deeps is greater, though their brilliant
glow, when lying upon the decks of the exploring ships, is no guide to
the possible intensity of their light in the pressure under which they
live. Many of the deep-sea species possess light-projecting organs in
numbers and perfection unrivalled by the shallow-water forms. Some of
the fish have double rows of tiny lamps running the whole length of
their bodies, like the rows of port-holes in an ocean steamer’s sides.
These are supplemented by other sets of less clearly divided
light-organs, arranged in clusters and groups of fifty or a hundred.
Other deep-sea fishes have bull’s-eye lanterns set beneath their eyes,
projecting their light “full-a-head.” Sections cut through these
extraordinary organs show that above the phosphorus-burning vessel lies
first a layer of “reflectors,” and lastly, a lens for concentrating the
beams. Perhaps the strangest development of this power of illumination
is in an angler-fish, found at a depth of 14,700 feet. Like the other
“anglers,” it has a huge mouth armed with long uneven teeth, and a
pendent “fishing-rod” tentacle which attracts other fish like a bait. In
the shallow-water “anglers” this tentacle resembles something edible by
fish. In the deep-water species it is fitted with an organ which is
supposed to be a phosphorus lamp, and to play the part of a
“Will-o’-the-Wisp” in attracting little fishes to the angler’s jaws.
The phosphorescent power is by no means confined to the fishes proper of
the deep sea. Starfish and most of the various forms of zoophytes
possess it, though in less perfect organs. One poured out “clouds of a
pale-blue, highly luminous substance, which not only illuminated the
observer’s hands and surrounding objects in the vessel in which it was
confined, but finally communicated a luminosity to the water itself;”
another threw out light of a brilliant green, coruscating from the
centre, now along one arm, now along another. In view of the
phosphorescence even of the surface of the sea when full of luminous
creatures, it is not rash to conclude that the eternal night of the
abyss is in places lighted with sufficient brilliance by its
phosphorescent zoophytes and fishes. Where these are few or absent,
there must be darkness either partial or complete. Hence we are
presented with the perfectly reconcilable contradiction of deep-sea
creatures with eyes of high development, and others with no eyes at all;
one species possessing eyes with four thousand facets, while crabs and
prawns are found totally blind, like the fish of subterranean caverns.
Those which carry lamps themselves, or live among luminous creatures,
not only retain their eyes, but are supplied with organs of abnormal
power in order to use to the utmost the phosphorous beams. The presence
of bright colouring in the deep-sea forms is also explained in the same
way, so far as colour is related to the presence of light. There is
little difference in the hues of deep-sea and shallow-water species,
except that shades of red are more frequent in the former, possibly
because red is the complementary colour of the phosphorescent beams.
It is in the leading facts which make such minor developments possible
that the wonder and significance of these discoveries lie,—in the
defiance of such physical obstacles as are set to life by enormous
pressure, and in the artificial lighting of the abysmal darkness by the
invading creatures. Sir Richard Owen once suggested an extension of the
limits of terrestrial life, by pointing out that the light of the planet
Jupiter was suited to the form of the vertebrate eye. When the mind
which has once grasped the physical conditions of the ocean abyss, is
confronted with the triumph of living creatures over such surroundings,
it no longer lies with it to reject as impossible the surmise that life,
which so transcends the limits set by ordinary experience to its scope
on earth, may also extend to the planets.
------------------------------------------------------------------------
THE LION HOUSE AT THE ZOO.
[“_Hic habitat leones._”—Old Map of Central Africa.]
JUST fifty years ago, when the best means of keeping wild animals in
health and vigour when confined was still matter for experiment, an
interesting set of statistics of the length of life of the large
_felidæ_ in the Gardens was submitted to the Society by Mr. Rees. It
appeared from the records of the menagerie that lions, leopards, tigers,
and pumas only lived, on an average, for two years in the Gardens, which
gave a rate of mortality of about one per month. The value of lions and
tigers was then about £150 each, and of leopards and pumas £15.
The system which led to this great mortality was one of confinement in
small stuffy cages, in a room artificially heated throughout the year,
and much was hoped from a complete change of treatment which had just
begun.
[Illustration:
PUMAS. From a photograph by Gambier Bolton.
]
The new principle was one of “free exposure to the outer air, with no
artificial heat whatever,” and the range of dens now known as the
“Terrace,” on either side of which the bears are kept, was built for the
accommodation of the lions and tigers. The cages do not strike us as
particularly roomy or comfortable now, but at that time they were looked
upon as unusually spacious, and the unfortunate carnivora, which had
been boxed up in stuffy rooms and narrow cages, soon felt the benefit of
the change. The African leopards, which were emaciated and sickly before
their removal, became plump and sleek in a fortnight, and the appetite
of all materially increased. The most convincing proof of this
gratifying change was that a tigress, feeling hungry in the night,
killed a tiger, and a puma did the same, and partly devoured its mate.
The Society took the hint, and increased their rations, and for some
time the new method of lion-culture answered well.
The rough-and-ready expedient of exposing the great cats to all the
changes of an English climate had a greater measure of success than
might have been expected. One is apt to forget that though the tropics
are the main home of the tiger and the leopard, both wander far into the
northern mountains, and that the former, if brought originally from
Turkestan or China, can stand an English winter as well as the Chinese
monkeys. During the year after the removal of the animals to their new
house there was not a single death, and the system promised so well that
artificial heat was for a time discontinued, both in the Monkey House
and the Giraffe House, except that given by open fires. That the health
of all the animals improved is shown by the list of creatures which
lived in the Gardens, including brown and black bears, leopards, and
ocelots.
The present Lion House, with its fine outdoor summer palaces, and its
indoor winter cages, in a house warmed with hot water, is a combination
of the two previous systems, and so far as health goes it seems to leave
nothing to be desired. The Zoo of the future will probably contain lion
houses of vast size, in which the creatures are allowed to live together
in large numbers. This is the system adopted by the largest owner of
wild animals in the world, Mr. Carl Hagenbeck, of Hamburg and New York.
In his gardens at Hamburg, six lions, two Bengal tigers, and one from
Siberia, live harmoniously in society with a polar bear, a Thibetan
bear, and a number of leopards. The chance of a battle royal at meal
time seems too great to be risked; but Mr. Hagenbeck says, that provided
the animals are associated when quite young, and that each addition to
the family is a young one, there is no danger. Meantime the space and
freedom of the great cages, and the absence of that _ennui_ to which
animals are subject when confined separately, or even in pairs, have the
best effect on their growth and vivacity. In the Hamburg cage the polar
bear will play and romp with the tigers for hours, and most wonderful
exhibitions of strength may be seen daily in these wrestling matches
between such gigantic and dissimilar creatures.
Mr. Hagenbeck is the Moltke of the wild animal trade. His menagerie at
Chicago attracted more visitors even than the “gigantic wheel,” mainly
because the creatures had more liberty and more space than they enjoy in
any other “gardens”; and it is probable that he will effect a marked
change in the modes of animal exhibitions now in use.
Meantime, whether in summer or winter, the Lion House is perhaps better
worth seeing than any branch of the Society’s menagerie.
Few public characters are “at home” to visitors during so many hours of
the day as its inmates; who might with justice enter a protest against
the incivility of the public, which insists on taking the notice that
“The lions will be fed at three o’clock,” as a pressing invitation to be
spectators of their manners at mealtimes. Yet the economy of the Lion
House so far differs from the ordinary life of the other inmates of the
Zoo that, for an undiscerning public which wants excitement and has no
time for observation, there is every inducement to confine its visits to
a particular hour. The cattle-sheds, the Antelope House, the Monkey
Palace, or the Aviaries, present much the same appearance at any time of
the day. The pleasant round of comfort—eating, drinking, playing, or
sleeping—goes on without variety or long cessation. But the life of the
great carnivora is ordered differently, and with greater exactness. In
the morning, in the Lion House, all is quiet. The animals are resting or
sleeping, and the only visitors are artists or photographers, whom the
lions “oblige” with a sitting at a cheaper rate than any professional
models in the trade. We wonder in how many characters the old Nubian
lion, “Prince,” appeared? He has striven with Hercules, carried Una,
been vanquished by Samson, and shot by Nimrod. He has roared at Daniel,
and eaten martyrs innumerable; and he still lives on canvas to entertain
Androcles in his den, or dies, the last of his race, in the desert
cavern of some artist’s fancy.