ANIMAL LIFE IN THE SEA--MEDUSAE--FOOD OF THE WHALE--PHOSPHORIC LIGHT--
CAUSE THEREOF--LUMINOSITY OF THE OCEAN.
Reference has elsewhere been made in this volume to the immense amount
of animal life that exists in the ocean, not only in the form of fish of
all sizes, but in that of animalcules, which, although scarcely visible
to the naked eye, are, in some cases, so innumerable as to give a
distinct colouring to the water.
The _Medusae_, or, more familiarly, sea blubbers, are seen in the waters
that lave our own shores. They are of various sizes, from that of a
large plate to a pin-head. They are almost colourless, like clear
jelly, and when carelessly observed, seem to be dead objects drifting
with the tide; but a closer observation shows that they are possessed of
life, though not of a particularly active kind, and that they swim by
alternate contractions and expansions of their bodies. These creatures
constitute a large part of the whale's food. Some of them are flat,
some semi-globular, others are bell-shaped, while some have got little
heads and small fins. Of these last it is said that each little
creature has no fewer than three hundred and sixty thousand minute
suckers on its head with which it seizes its prey. When we think of the
exceeding smallness of the creatures thus preyed upon, and consider the
fact that each little thing must obtain food by making war upon some
creatures still smaller than itself, we are led almost in spite of
ourselves into that mysteriously metaphysical question--infinitesimal
_divisibility_; which may be translated thus--the endless division and
subdivision of atoms. This subject has puzzled the heads of the
profoundest philosophers of all ages; we will not, therefore, puzzle our
readers with it any further.
Scoresby tells us that the colour of the Greenland Sea varies from
ultramarine blue to olive-green, from the purest transparency to
striking opacity; and that these colours are permanent, and do not
depend on the state of the weather, but on the quality of the water. He
observed that whales were found in much greater numbers in the green
than in the blue water; and he found, on examining the former with the
microscope, that its opacity and its colour were due to countless
multitudes of those animalcules on which the whale feeds.
We need scarcely remark that it is utterly beyond the power of man to
form anything approaching to a correct conception of the amount of
_life_ that is thus shown to exist in the ocean. Although it has
pleased the Creator to limit our powers, yet it has also pleased him to
leave the limit of those powers undefined. We may not, indeed, ever
hope in this life to attain to perfect knowledge, nevertheless, by
"searching" we may "find out wisdom;" and certain it is, that, although
there undoubtedly must be a point of knowledge on any given subject
which man cannot reach, there is in man a power incessantly to extend
his knowledge and increase his powers of conception, by each successive
effort that he makes in his course from the cradle to the grave.
Even although we were told the exact number of the little creatures that
inhabit the sea, we could not, by any simple effort of the mind, however
powerful, form a conception of what that number implied. We might shut
ourselves up like the hermits of old, abstract our thoughts from all
other things, and ponder the subject for weeks or months together, and
at the termination of our effort we should be as wise as we were at its
commencement, but no wiser. But by searching round the subject, and
comparing lesser things with greater, although we should still fail to
arrive at a full comprehension of the truth, we may advance our powers
of conception very considerably beyond the point attained by our first
effort; and which point, as we have said, could not be surmounted by a
hair's breadth by the mere exertion of simple or abstract thought.
Dr Scoresby's remarks on the subject of animal life in the ocean, are
so graphic and curious that we extract the passages verbatim from the
admirable memoir of that gentleman, written by his nephew. He says:
"I procured a quantity of snow from a piece of ice that had been washed
by the sea, and was greatly discoloured by the decomposition of some
peculiar substance upon it. A little of this snow dissolved in a
wine-glass appeared perfectly nebulous--the water being found to contain
a great number of semi-transparent spherical substances, with others
resembling small portions of fine hair. On examining these substances
with a compound microscope, I was enabled to make the following
observations:--
"The semi-transparent globules appeared to consist of an animal of the
medusa kind. It was from one-twentieth to one-thirtieth of an inch in
diameter. Its surface was marked with twelve distinct patches, or
nebulae, of dots of a brownish colour. These dots were disposed in
pairs, four pairs or sixteen pairs alternately, composing one of the
nebula. The body of the medusa was transparent. When the water
containing these animals was heated, it emitted a very strong odour, in
some respects resembling the smell of oysters when thrown on hot coals,
but much more offensive.
"The fibrous or hair-like substances were more easily examined, being of
a darker colour. They varied in length from a point to one-tenth of an
inch; and when highly magnified, were found beautifully moniliform.
Whether they were living animals, and possessed of locomotion, I could
not ascertain. They possessed the property of decomposing light, and in
some cases showed all the colours of the spectrum very distinctly.
"I afterwards examined the different qualities of sea water, and found
these substances very abundant in that of an olive-green colour; and
also occurring, but in lesser quantity, in the bluish-green water. The
number of medusae in the olive-green water was found to be immense.
They were about one-fourth of an inch asunder. In this proportion, a
cubic inch of water must contain 64; a cubic foot 110,592; a cubic
fathom 23,887,872; and a cubic mile about 23,888,000,000,000,000."
Of course we have, in the last two numbers, reached the utterly
incomprehensible; but Dr Scoresby goes into comparisons which help us a
little, at least to ascertain how hopelessly beyond our conceptions such
numbers are.
"From soundings made in the situation where these animals were found, it
is probable the sea is upwards of a mile in depth; but whether these
substances occupy the whole depth is uncertain. Provided, however, the
depth to which they extend be but two hundred and fifty fathoms, the
above immense number of one species may occur in the space of two miles
square. It may give a better conception of the amount of medusae in
this extent, if we calculate the length of time that would be requisite,
with a certain number of persons, for counting this number. Allowing
that one person could count a million in seven days, which is barely
possible, it would have required that eighty thousand persons should
have started at the creation of the world to complete the enumeration at
the present time!
"What a stupendous idea this gives of the immensity of creation, and of
the bounty of Divine Providence in furnishing such a profusion of life
in a region so remote from the habitations of men!
"The larger portion of these medusae, consisting of transparent
substances of a lemon-yellow colour, and globular form, appeared to
possess very little power of motion. Some of them were seen advancing
by a slight waving motion, at the rate of a hundred and eightieth of an
inch in a second; and others, spinning round with considerable celerity,
gave great interest and liveliness to the examination. But the
progressive motion of the most active, however distinct and rapid it
might appear under a high magnifying power, was, in reality, extremely
slow; for it did not exceed an inch in three minutes. At this rate they
would require one hundred and fifty-one days to travel a nautical mile.
"The vastness of their numbers, and their exceeding minuteness, are
circumstances, discovered in the examination of these animalcules, of
uncommon interest. In a drop of water examined by a power of 28.224
(magnified superficies) there were fifty in number, on an average, in
each square of the micrometer glass, of an eight hundred and fortieth of
an inch; and as the drop occupied a circle on a plate of glass
containing 529 of these squares, there must have been, in this single
drop of water, taken out of the yellowish-green sea, in a place by no
means the most discoloured, about 26,450 animalcules. Hence, reckoning
sixty drops to a dram, there would be a number in a gallon of water
exceeding, by one half the amount of the population of the whole globe!
It gives a powerful conception of the minuteness and wonders of
creation, when we think of more than twenty-six thousand animals living,
obtaining subsistence, and moving perfectly at their ease, without
annoyance to one another, in a single drop of water... A whale requires
a sea, an ocean, to sport in. About one hundred and fifty millions of
these animalcules would have abundant room in a tumbler of water!"
But besides furnishing food to the whale, and, no doubt, to many other
of the inhabitants of the deep, those medusae are the cause of the
phosphorescent light that sometimes glows on the ocean with resplendent
brilliancy. We see this light oftentimes on our own coasts. It is
usually of a pale bluish-white colour, more or less intense, apparently,
according to the condition of the creatures by which it is emitted. It
can only be seen at night. We have seen it on the west coast of
Scotland, so bright that the steamer in which we sailed left behind her
what appeared to be a broad highway of liquid fire.
At times it requires vigorous motion, such as takes place when an oar is
dipped, a stone thrown, or paddle-wheels dashed into the water; but at
other times, the mere motion of the ocean swell, even in calm weather,
is sufficient to stir up the lambent light and cause the crest of every
undulation to glitter as if tipped with burnished silver. In such
circumstances we have seen the ends of the oars of a boat silvered with
it when lifted out of the wave, and the drops which fell from them
before being redipped resembled the most beautiful diamonds.
Mr P.H. Gosse, in his interesting work, "The Ocean," gives the
following account of this luminosity of the sea, as witnessed by himself
on one occasion:
"In a voyage to the Gulf of Mexico, I saw the water in those seas more
splendidly luminous than I had ever observed before. It was indeed a
magnificent sight, to stand on the fore-part of the vessel and watch her
breasting the waves. The mass of water rolled from her bows as white as
milk, studded with those innumerable sparkles of blue light. The
nebulosity instantly separated into small masses, curdled like clouds of
marbles, leaving the water between of its own clear blackness; the
clouds soon subsided, but the sparks remained. Sometimes one of these
points, of greater size and brilliancy than the rest, suddenly burst
into a small cloud of superior whiteness to the mass, and be then lost
in it. The curdling of the milky appearance into clouds and masses, and
its quick subsidence, were what I had never before observed elsewhere."
Many scientific travellers have carefully examined this subject, and we
believe that all agree in referring this beautiful appearance to the
medusae. One gentleman drew a bucketful of water from the sea when it
was in this condition, and found, on examining it in a dark place, that
the little creatures "could be distinctly seen emitting a bright speck
of light. Sometimes this was like a sudden flash, at others appearing
like an oblong or round luminous point, which continued bright for a
short time, like a lamp lit beneath the water and moving through it,
still possessing its definite shape, and then suddenly disappearing.
When the bucket was sharply struck on the outside, there would appear at
once a great number of these luminous bodies, which retained their
brilliant appearance for a few seconds, and then all was dark again.
They evidently appeared to have it under their own will, giving out
their light frequently, at various depths in the water, without any
agitation being given to the bucket. At times might be seen minute but
pretty bright specks of light, darting across a piece of water and then
vanishing; the motion of the light being exactly that of the cyclops
through the water. Upon removing a tumblerful from the bucket, and
taking it to the light, a number of cyclops were accordingly found
swimming and darting about in it."
We have given the above quotation at full length, because it proves, in
an interesting manner, the fact that phosphorescence, or luminosity, of
the sea is actually produced by multitudes of living creatures. We
cannot pass from it, however, without expressing our difference of
opinion in regard to the power of the medusae to emit their light "at
will."
It seems much more probable that the light is the result of passion and
action. When a man's feelings are strongly roused, whether pleasurably
or otherwise, he usually starts into action under a sudden impulse,
which sends the blood violently through his veins, causing his face to
become flushed and _red_. This reddening is not the result of will. It
is the unavoidable result of passionate impulse, and could not possibly
be produced by an effort of the will.
It is well known that electric fluid permeates the bodies of all
animals, more or less; and it is quite conceivable that under the
influence of nervous impulse one creature should become luminous, while
another only becomes red. Man leaps and sings for joy; and the result
is, that the actions cause his countenance to glow with _colour_. The
marine animalcule, experiencing a sudden influx of delight, darts hither
and thither under the strong impulse of its exuberant glee; and the
result is, that its little body gleams with _light_. Vigorous action is
the direct cause of the emission of light in the one case, just as
vigorous action is the direct cause of the suffusion of the countenance
in the other. But in both cases the primary cause is passion--at least
so it seems to us.
No doubt fear as well as joy may create vigorous action, and produce the
same result; but as we know that, as a general rule, there is much more
of joy than of fear dwelling at all times in the hearts of God's
creatures, we can well believe that the amount of luminosity produced in
the sea by the latter passion is immeasurably smaller than that produced
by the former. We are thus, therefore, set free to indulge in the
pleasing reflection that when we behold that magnificent gleaming of the
sea, which almost resembles liquid silver reflecting the stars of
heaven, we are witnessing the frolicsome and joyous gambols of those
myriads of little beings to whom the beneficent Creator has assigned the
ocean as their dwelling-place.
The theory which we have ventured to propound in regard to vigorous
impulse (whether of joy or fear) being the cause of eliciting
luminosity, is supported in some degree by the remark in our last
quotation, that when the bucket was sharply struck, there appeared at
once a number of luminous bodies, which shone for a few seconds, and
then disappeared. Undoubtedly the poor little things got a fright when
their residence was sharply assailed in such an unusual manner; their
energies were roused, and their light emitted. Then, as they gradually
calmed down, their light disappeared.
We are further told that when a drop of sulphuric acid was put into a
tumbler of water, "several bright flashes were seen." This, we venture
to think, was somewhat similar to the putting of a few drops of brandy
and water into the human stomach; the usual result of which is, as we
all know, to produce several bright flashes of wit, if not of light, or
of something at least meant to be remarkably luminous!
But this luminosity is not entirely confined to the minute creatures of
the sea. Some fish have the power of emitting light. Some species of
the shark emit a greenish light; and the sun-fish is said, when seen
down in the sea on a dark night, to glow like a white-hot cannon-ball.
Fish when dead and putrid frequently glow in the dark with a truly
magnificent light, as can be proved by every one who will take the
trouble to procure several kinds of fish, and keep them, for the purpose
of proving the fact, in a dark closet.
Of all the minute inhabitants of the deep, that which is to our mind the
most curious, both as to its nature and its stupendous works, is the
coral insect. This creature is much too important to be dragged in at
the tail of a chapter. We will, therefore, commence its history in a
new one.