MULTITUDINOUS LIFE
“This great and wide sea, wherein are things creeping innumerable,
both small and great beasts.”--Ps. civ. 25.
“The dense immensity
Of ever-stirring Life, in thy strange forms
Of fish and shell and worm and oozy mud.”--KINGSLEY.
Some thirty or forty years ago the knowledge which man had of the
“Great Deep” was practically _nil_.
We know a good deal more now, thanks to the famous voyage of the
_Challenger_, and to many other observations, though still the full sum
of our information is small compared with the much that we do not know.
In the year 1872 the good ship _Challenger_ quitted British shores for
her long tour of discovery. During nearly three years and a half she
cruised about the world, dipping her instruments into the water at
frequent intervals, measuring the depths, studying the temperatures,
making note of other conditions, and bringing up from the ocean-bed
materials whereby to judge of the state of that dark nether-world,
hidden from our eyes by intervening miles of water.
Three and a half years of steady work; hundreds upon hundreds of
soundings; thousands upon thousands of miles traversed; tens of
thousands of specimens hauled up; days and weeks and months devoted to
unremitting study of those specimens! This is what the _Challenger_
Expedition meant. No wonder our knowledge of the Under-Ocean has grown
by leaps.
And yet no wonder it is still confined within narrow limits. So
enormous is the extent of the Ocean,--so few comparatively are the
parts which have been under close examination!
Imagine a monster giant striding with vast steps over the sea, and at
intervals of a mile or two dipping a long arm into the depth, to bring
away a handful of whatever might lie upon the bed below. No doubt he
might and would thus learn a good deal that he had not known before.
Still, at the best, tens of thousands of square miles would lie around
in all directions, untouched by his searching fingers.
This is very much what the Expedition was able to do. A handful here
and a handful there was brought up, as a specimen of what might be
found below. But tens of thousands of square miles, to north and south
and east and west, remained untouched.
None the less, from these occasional “dips,” however few by comparison
with reaches not examined, we know far more than our forefathers could
have dreamt of as within the bounds of possibility.
Instruments, many and complicated, are used in deep-sea researches--far
too many and too complicated to be described here. Two or three may be
mentioned.
Sounding-machines proper are largely employed, sometimes carrying
water-bottles, and always brass tubes, weighed down by “sinkers,” which
remain behind when the tubes are drawn up full of mud or ooze.
Small dredges are dragged along the sea-bottom, gathering whatever may
lie there loosely, and bringing it to the surface.
Trawls also are necessary, with beams from ten to seventeen feet in
length. Such trawls, held by strong steel cables thousands of fathoms
long, can often lift seven tons of material.
Into the bottom of a dredge-bag and of a trawl-net fine cloth is
frequently sewn, so that mud and small animals may not slip through and
be lost.
[Illustration: DRAGGING THE TOW-NET TO CATCH MINUTE SURFACE ANIMALS
Note sailors with small nets]
[Illustration]
[Illustration: BEAM-TRAWL AND TOW-NET EMPLOYED IN DEEP-SEA RESEARCH
_Face page 188_
]
Immense supplies have been thus dredged and hauled up from the
bottom of the sea. Muds and oozes, sands and pebbles, stones and
rocks, shelly deposits, volcanic deposits, remains innumerable of
dead plants, remains still more abundant of animals, including
earbones of whales and teeth of sharks, and more rarely other parts
of animal-skeletons--large, small, microscopic, these all have been,
with infinite care, with infinite patience, sorted and examined and
classified.
Teeth and earbones! But where are the great shark-skeletons? Where are
the mighty bone frameworks of whales?
If a whale’s earbones lie here, surely here also must have sunk
the enormous carcase. Yet all the rest has vanished. All has been
dissolved--disintegrated--eaten up, as it were, by the black and silent
waste of water. Sea-water has an extraordinary dissolving power, much
intensified by added pressure at great depths, and few substances can
long withstand that power. Not even the massive skeletons of sharks
and whales, with the exception of the teeth and earbones, which are
formed of peculiarly hard material.
And never once, throughout the whole cruise, was any single bone of Man
brought up from the ocean-bed.
After all is this surprising? Where even whale-skeletons are mastered,
small chance can remain for a human skeleton to stand out long against
absorption.
The marvel is how tiny foraminifer shells can last as they do. The
majority no doubt disappear. Unless they reach the bottom quickly, and
are there covered up and protected, they must soon be dissolved.
Yet that vast numbers do thus escape we know by the masses of ooze
found over the sea-bottom; by the fifty millions or more of square
miles of the ocean-floor carpeted with coral muds and sands, and with
oozes of foraminifera and kindred shells.
Only down to a depth of about two miles. Beyond that, carbonate-of-lime
shells are seldom found. It is believed that these light shells take
as much as three or four days to sink one mile; and in about two miles
they all succumb to the power of sea-water. But the hard little diatom
cases are present in all depths, more especially in Earth’s colder
regions, where they abound most freely.
The ocean-bed has been described as one huge sepulchre, full of the
remains of once-living creatures. And this is true; yet by itself it
gives a very one-sided view. Not less is the ocean-bed to be described
as a world of abounding Life.
Everywhere, throughout the whole sea, in all parts, above and below
and between--near the surface, on the floor, in all intermediate
reaches--living creatures flourish in numbers past imagination.
Not everywhere equally. Here may be found a wonderful richness of
animal-life. There the explorer may alight on a barren region. Yet even
those parts more scantily supplied need not be always thus. Living
creatures in vast hordes, in enormous companies, drift to and fro, rise
upwards and sink downwards; and the district which to-day seems almost
devoid of life may to-morrow be thronged with active beings.
The Ocean’s inhabitants have been roughly divided into three Classes--
Deep-Sea Life, Intermediate Ocean Life, and Surface Ocean Life.
The first of these includes all animals which crawl upon the sea-bed,
or which live within about three hundred fathoms of it.
The second includes all animals which live between about three
hundred fathoms of the sea-bottom and three hundred fathoms of the
ocean-surface.
The third includes all animals which live within three hundred fathoms
of the surface, and those on shallow shores.
By far the greater number of living creatures appear to inhabit the
surface regions; and it may be that the next in number are those on and
near the ocean-bed. This, however, is uncertain. It is difficult to
judge about the intermediate depths. All creatures living there must be
extremely good swimmers, and they are very shy of nets.
We cannot readily picture to ourselves the manner of life which goes
on in those intermediate parts. Creatures there have, as it seems,
no connection with either the ocean-bed or with shallow shores--no
resting-place to which they may turn--in short, no home. Though one may
not realise the fact, few animals within our ken have not something in
the shape of a home, a _pied à terre_, to use a familiar term, though
that “terre” may be under water.
The very idea of a life spent always in swimming or floating through
boundless depths, never touching firm ground, having no kind of home or
retreat, suggests vagabondage, and sounds disconsolate.
It may be that the difficulty is at least partly met by those great
floating banks of living creatures which are often found.
Diatom-Banks have been already spoken of. But other animals of larger
growth also band together, forming vast companies. To each individual
in such a congeries the Floating Bank would be a home. It would matter
little to that individual whether the bank as a whole floated here or
drifted there, whether it rose at night to the surface of the sea, or
whether in daytime it sank lower to escape from the sun’s glare.
Many such banks of life belong strictly to the Surface Class rather
than to the Intermediate. But the want of a home applies equally to all
creatures who live a free and roving life in the Ocean, unattached to
shore or to sea-bed, whether they live above or below the three-hundred
fathom limit.
Another puzzling question has been as to how deep-sea creatures are
fed.
In Life on _terra firma_, generally, the work of plants is to make
ready food for animals. Many substances, which are needful for
animal-structure, cannot be taken in by them until broken up and
re-made by plants. And plants can only carry out this task in sunlight.
Where the light of the sun fails, there plant-life fails also.
But direct vegetable food is not always necessary. Arctic
animals--bears, seals, walruses,--cannot get it except at second
or third hand, through the bodies of other animals. Perhaps this
was forgotten by some who maintained that no animals could, by any
possibility, flourish in ocean’s greater depths.
Numberless observations have now thrust that theory on one side. By
the dredgings and trawlings of the _Challenger_, not to speak of later
explorations, it has been conclusively proved that, even down to great
depths, animal life is marvellously plentiful.
Two or three examples may be given. A single haul, made in water more
than a mile deep, brought up animals of two hundred different kinds.
Another haul, in a depth of two miles, had the same result. Another, in
a depth of three miles, brought up fifty different kinds. All these it
was known, by tokens learnt from close study and much experience, had
certainly lived near the bottom. Again, from depths of four miles many
creatures, including fishes, appeared. Even in a depth of over five
miles, signs of life were not lacking.
Who, after this, may venture to name a depth at which Life is
altogether impossible?
Although plants cannot live and grow in the darkness of nether ocean,
their decaying remains are incessantly raining downward from higher
levels. Animals in the intermediate parts, and perhaps also near
the sea-bed, can feed largely upon these falling sea-weeds. Immense
quantities are doubtless snapped up _en route_; but many also reach the
ocean-floor undevoured, since vegetable-remains often figure in the
muds and oozes brought up thence.
Deep-sea animals are very extensively eaters of mud and ooze and clay.
It does not sound like appetising fare, or what our grandparents used
to describe as “palatable.” But the palate of a deep-sea fish or crab
differs from that of a man; and since no better vegetable-food offers
itself, they are probably content.
That the said creatures do really subsist in a measure upon such
materials, is known for a fact. When drawn up to the surface, they are
found often to have their stomachs full of the mud or ooze or clay
which in that particular place carpets the ocean-bed.
Even in far shallower waters, not much removed from the “hundred-fathom
line,” though still beyond the region of living sea-weed, crabs dredged
up are found to have indulged freely in the same frugal rations.
There is of course no difficulty as to animal-food in any depth. The
fight for life goes on below, as above; and the weaker succumbs to the
stronger, or the less cunning to the more subtle, in the deep as within
reach of sunlight.