The Porifera, or Sponges, were formerly supposed to belong to the

vegetable kingdom, but their animal nature is now fully ascertained, for

modern researches have proved that the soft glairy substance with which

their skeleton is invested during life consists of "sarcode," similar to

that which forms the soft parts of the Foraminifera and Polycystina. It

is by this animated or organic gelatine, which can generally be pressed

out with the finger, and in some species is copious even to nauseousness,

that the solid parts of the sponge are deposited, and from it the whole

growth of the mass proceeds. The framework or skeleton of the Porifera is

usually composed of horny fibres of unequal thickness, which ramify and

interlace in every possible direction, anastomosing with each other so as

to form innumerable continuous cells and intricate canals, the walls of

which in the recent sponge are crusted over with the gelatinous living

cortex.

[Illustration: Single interspace or open cell, and surrounding finer

meshwork of the skeleton of a sponge.]

[Illustration: Needle-like and starred spicula of a Tethea. (Highly

magnified.)]

Generally this fibrous mass is interwoven with numerous mineral spicules

of a wonderful elegance and variety of forms, for their shapes are not

only strictly determinate for each species of sponge but each part of

the sponge, it is believed, has spiculæ of a character peculiar to

itself. Sometimes they are pointed at both ends, sometimes at one only,

or one or both ends may be furnished with a head like that of a pin, or

may carry three or more diverging points, which sometimes curve back

so as to form hooks. Sometimes they are triradiate, sometimes stellar;

in some cases smooth, in others beset with smaller spinous projections

like the lance of the saw-fish. In many species they are embedded in the

horny framework; in others, as, for instance, in Tethea Cranium, or in

Halichondria, they project from its surface like a tiny forest of spears.

They are generally composed of silex or flint, but in the genus Grantia

they consist of carbonate of lime. Though the skeleton of most sponges is

formed both of horny fibres and of mineral spicules yet the proportions

of these two component parts vary considerably in different species. In

the common sponge, for instance, the fibrous skeleton is almost entirely

destitute of spicules, a circumstance to which it owes the flexibility

and softness that render it so useful to man, while they predominate

in the Halichondriæ, and sometimes even, as in the Grantiæ, completely

supersede the horny fabric.

[Illustration: Minute portion of the surface of Tethea Cranium,

magnified, spicula projecting beyond the surface.]

[Illustration: Halina papillaris.

Currents passing inwards through the pores (_a a_), traversing the

internal canals (b), and escaping by the larger vents (_c_, _d_).]

On examining a sponge, the holes with which the substance is everywhere

pierced may be seen to be of two kinds; one of larger size than the rest,

few in number, and opening into wide channels and tunnels which pierce

the sponge through its centre; the other minute, extremely numerous,

covering the wide surface, and communicating with the innumerable

branching passages which make up the body of the skeleton. Through the

smaller openings or pores the circumambient water freely enters the

body of the sponge, passes through the smaller canals, and, ultimately

reaching the larger set of vessels, is evolved through the larger

apertures or oscula. Thus by a still mysterious agency (for the presence

of cilia has as yet been detected but in one genus of full-grown marine

sponges) a constant circulation is kept up, providing the sponge with

nourishing particles and oxygen, and enabling its system of channels

to perform the functions both of an alimentary tube and a respiratory

apparatus.

Dr. Grant describes in glowing terms his first discovery of this highly

interesting phenomenon: "Having put a small branch of sponge with some

sea-water into a watch-glass, in order to examine it with the microscope,

and bringing one of the apertures on the side of the sponge fully into

view, I beheld for the first time the spectacle of this living fountain,

vomiting forth from a circular cavity an impetuous torrent of liquid

matter, and hurling along in rapid succession opaque masses, which it

strewed everywhere around. The beauty and novelty of such a scene in the

animal kingdom long arrested my attention, but after twenty-five minutes

of constant observation, I was obliged to withdraw my eye from fatigue,

without having seen the torrent for one instant change its direction or

diminish in the slightest degree the rapidity of its course. I continued

to watch the same orifice at short intervals for five hours, sometimes

observing it for a quarter of an hour at a time, but still the stream

rolled on with a constant and equal velocity."

Subsequent observations have proved that the living sponge has the power

of opening and closing at pleasure its oscula, which are capable of

acting independently of each other, thus fully establishing the animal

nature of these simple organisations, in whom latterly even traces of

sensibility have been detected, such as one would hardly expect to meet

with in a sponge. For these creatures, as we are entitled to call them,

are able to protrude from their oscula the gelatinous membrane which

clothes their channels, and on touching these protruded parts with a

needle, they were seen by Mr. Gosse to shrink immediately--a proof that

the sponge, however low it may rank in the animal world, is yet far from

being so totally inert or lifeless as was formerly imagined.

The propagation of the sponges is provided for in a no less wonderful

manner than their respiration and nourishment. Minute globular particles

of sarcode sprout forth as little protuberances from the interior of

the canals. As they increase in size, they are gradually clothed with

vibratile cilia, and, finally detaching themselves, are cast out through

the oscula into the world of waters. Here their wanderings continue for

a short time, until, if they be not devoured on the way, they reach some

rock or submarine body on which, tired of their brief erratic existence,

they fix themselves for ever, and, bidding adieu to all further rambles,

lead henceforth the quiet sedentary life of their parents. In this manner

the sponges, which otherwise would have been confined to narrow limits,

spread like a living carpet over the bottom of the seas, and in spite of

their being utterly defenceless, maintain their existence from age to

age. At the same time they serve to feed a vast number of other marine

animals, for the waters frequently swarm with their eggs, and these

afford many a welcome repast to myriads of sessile molluscs, annelides,

polyps, and other creatures small or abstemious enough to be satisfied

with feasting on atoms.

Sponges inhabit every sea and shore, and differ very much in habit of

growth. For whilst some can only be obtained by dredging at considerable

depths, others live near the surface, and others, again, attach

themselves to the surfaces of rocks and shells between the tide marks.

Like the corals, they revel in every variety of shape and tint, imitate

like them every form of vegetation, and adorn like them the submarine

grounds with their fantastic shrubberies. The fine collection of West

Indian sponges exhibited in the Crystal Palace, but to which fancy must

add the additional ornament of colour, may serve to give some idea of

their prodigal versatility of growth. More than sixty different species

have been discovered in the British waters alone, and as they go on

increasing in numbers, size, and beauty, until they attain their highest

development along the shores of the tropical ocean, they no doubt hold

a conspicuous rank among the living wonders of the sea. The branched

sponges, with a compact feltred tissue, are more common than others in

the colder maritime domains, where the species of a loose texture, which

grow in large massive forms, either do not exist or are very rare. Many

sponges are of considerable size, such as the vase-like tropical species

known under the name of Neptune's cup; others are almost microscopical;

and while by far the greater number grow superficially from a solid base,

some penetrate like destructive parasites into the texture of other

animals. Thus the _Halichondria celata_ establishes itself in the small

holes which some of the smaller annelides drill in the shell of the

oyster, eat further and further into the unfortunate mollusc's vitals,

causing the softer parts of the shell to rot away, and spread through

its whole substance, like the dry-rot fungus through a solid beam of

timber, until, sinking under the weight of his misery, the poor victim

perishes, and his loosened shell is cast to the mercy of the waves. On

the other hand, some marine Acorn-shells nestle habitually in a sponge,

the normal construction of the base of the shell being altered to suit

the peculiarities of its habitation, so that in this instance, as in many

others, there is a foreseen relation between two very dissimilar animals.

Amongst the reticulated fibres of its spongy dwelling, the Acorn-shell

finds a secure refuge in its infant state, and is soon enclosed by the

growing fabric of the sponge-animal, except a small opening, which is

kept clear by the vortex occasioned by the constant motion of its feelers

or tentacula.

But very few of the manifold species of sponges are of any use to man.

The common sponge of commerce (_Spongia communis_), so serviceable in

our households, is most abundant in the Lycian seas, where it is found

attached to rocks at various depths between three fathoms and thirty.

When alive, it is of a dull bluish black above, and dirty white beneath.

There are several qualities, possibly indicating as many distinct species.

"The most valued kinds," says Edward Forbes, "are sought for about the

Gulf of Macri, along the Carian coast, and round the opposite islands.

The species which live immediately along the shore near the water's edge,

though often large, are worthless. These are of many colours; some of

the brightest scarlet or clear yellow form a crust over the faces of

submarine rocks; others are large and tubular, resembling holothuriæ

in form and of a gamboge colour, which soon turns to dirty brown when

taken out of the water; others are again lobed or palmate, studded with

prickly points, and perforated at intervals with oscula. These grow to

a considerable size, but, like the former, are useless, since their

substance is full of needles of flint."

Large quantities of excellent sponge (_Spongia usitatissima_) are

likewise imported from the West Indies.

CHAP. XIX.

MARINE PLANTS.

The Algæ.--Zostera marina.--The Ulvæ and Enteromorphæ.--The Fuci.--The

Laminariæ.--Macrocystis pyrifera.--Description of the Submarine

Thickets at Tierra del Fuego.--Nereocystis lutkeana.--The Sargasso

Sea.--The Gathering of edible Birds'-nests in the marine Caves of

Java.--Agar-Agar.--The Florideæ.--The Diatomaceæ.--Their importance in

the economy of the Seas.

The dry land develops the most exuberant vegetation on the lowest

grounds, the plains and deep valleys, and the size and multiplicity of

plants gradually diminish as we ascend the higher mountain regions, until

at last merely naked or snow-covered rocks raise their barren pinnacles

to the skies: but the contrary takes place in the realms of ocean; for

here the greater depths are completely denuded of vegetation, and it

is only within 600 or 800 feet from the surface that the calcareous

nullipores begin to cover the sea-bottom, as mosses and lichens clothe

the lofty mountain-tops. Gradually corallines and a few algæ associate

with them, until finally about 80 or 100 feet from the surface begins the

rich vegetable zone which encircles the margin of the sea. The plants

of which it is composed do not indeed attain the same high degree of

development as those of the dry land, being deprived of the beauties of

flower and fruit: but as the earth at different heights and latitudes

constantly changes her verdant robe, and raises our highest admiration

by the endless diversity of her ornaments, thus also the forms of the

sea-plants change, whether we descend from the brink of ocean to a

greater depth, or wander along the coast from one sea to another; and

their delicate fronds are as remarkable for beauty of colour and elegance

of outline, as the leaves of terrestrial vegetation.

The difference of the mediums in which land- and sea-plants exist

naturally requires a different mode of nourishment, the former

principally using their roots to extract from a varying soil the

substances necessary for their perfect growth, while the latter absorb

nourishment through their entire surface from the surrounding waters, and

use their roots chiefly as holdfasts.

The constituent parts of the soil are of the greatest importance to

land-plants, to whose organisation they are made to contribute; while to

the sea-plant it is generally indifferent whether the ground to which it

is attached be granite, chalk, slate, or sandstone, provided only its

roots find a safe anchorage against the unruly waters.

Flat rocky coasts, not too much exposed to the swell of the waves, and

interspersed with deep pools in which the water is constantly retained,

are thus the favourite abode of most algæ, while a loose sandy sea-bottom

is generally as poor in vegetation as the Arabian desert.

But even on sandy shores extensive submarine meadows are frequently

formed by the Grass Wrack (_Zostera marina_), whose creeping stems,

rooting at the joints and extending to a considerable depth in the sand,

are admirably adapted for seeming a firm position on the loose ground.

Its long riband-like leaves, of a brilliant and glossy green, wave freely

in the water, and afford shelter and nourishment to numerous marine

animals and plants. In the tropical seas it forms the submarine meadows

on which the turtles graze, and in the North of Europe it is used for the

manufacture of cheap bedding. It also furnishes an excellent material for

packing brittle ware.

Sea-weeds are usually classed in three great groups, green,

olive-coloured, and red; and these again are subdivided into numerous

families, genera, and species.

On the British coasts alone about 400 different species are found,

and hence we may form some idea of the riches of the submarine flora.

Thousands of algæ are known and classified, but no doubt as many more at

least still wait for their botanical names, and have never yet been seen

by human eye.

The _Green_ sea-weeds, or Chlorospermeæ, generally occur near high-water

mark, and love to lead an amphibious life, half in the air and half in

salt-water. The delicate Enteromorphæ, similar to threads of fine silk,

and the broad brilliant Ulvæ, which frequently cover the smooth boulders

with a glossy vesture of lively green, belong to this class. Many of them

are remarkable for their wide geographical distribution. Thus the _Ulva

latissima_ and the _Erderomorpha compressa_ of our shores thrive also

in the cold waters of the Arctic Sea, fringe the shores of the tropical

ocean, and project into the southern hemisphere as far as the desolate

head-lands of Tierra del Fuego. But few animals or plants possess so

pliable a nature, and such adaptability to the most various climates.

The _Olive-coloured_ group of sea-weeds, or Melanospermeæ, plays a much

more considerable part in the economy of the ocean. The common fuci,

which on the ebbing of the tide impart to the shore cliffs their peculiar

dingy colour, belong to this class; as well as the mighty Laminariæ,

which about the level of ordinary low water, and one or two fathoms

below that limit, fringe the rocky shore with a broad belt of luxuriant

vegetation.

The first olive-coloured sea-weed we meet with on the receding of the

flood is the small and slender _Fucus canaliculatus_, easily known by

its narrow grooved stems and branches, and the absence of air-vessels.

Then follows _Fucus nodosus_, a large species, with tough thong-like

stems, expanding at intervals into knob-like air-vessels, and covered

in winter and spring with bright yellow berries. Along with it we find

the gregarious _Fucus vesiculosus_, with its forked leaf traversed by a

midrib, and covered with numerous air-vessels situated in pairs at each

side of the rib. Finally, about the level of half-tide, a fourth species

of fucus appears, _Fucus serratus_, distinguished from all the rest by

its toothed margin and the absence of air-vessels.

These four species generally occupy the littoral zone of our sea-girt

isle, being found in greatest abundance on flat rocky shores,

particularly on the western coasts of Scotland and Ireland, where they

used formerly to be burnt in large quantities for the manufacture of kelp

or carbonate of soda, which is now obtained by a less expensive process.

In Orcadia alone more than 20,000 persons were employed during the whole

summer in the collection and incineration of sea-weeds, a valuable

resource for the poverty-stricken islanders, of which they have been

deprived by the progress of chemical science.

The fuci are, however, still largely used, either burnt or in a fermented

state, as a valuable manure for green crops. Thus every year several

small vessels are sent from Jersey to the coast of Brittany, to fetch

cargoes of sea-weeds for the farmers of that island.

A RUSSIAN OFFICIAL, ATTENDED BY A SOLDIER, COLLECTING ALGÆ ON THE SHORES

OF THE NORTH PACIFIC.

The annexed plate is taken from the frontispiece of the magnificent

folio volume by Messrs. Ruprecht and Postels, on the Algæ of the North

Pacific. This work, in which even the largest of the marine plants of

that region are represented of their natural size, was published at

the expense of the Russian Government, and copies were presented to

some of the principal libraries of Europe.

In the middle distance, a Russian official belonging to one of the

settlements is seen gathering algæ, attended by a soldier.

In the front of the picture the water is supposed to be so clear as to

show distinctly the growth of sea-weeds of various kinds, which clothe

the submarine rocks in that region. Some species of these have been

added to the number shown in the original composition.

In the centre, with the light fully upon them, are streaming plants

of a gigantic _Alaria_, whose fronds sometimes extend to a length

of 40 feet. Immediately beneath it, to the right, is the curiously

perforated _Agarium Gmelini_, the singular perforations of which are

indicated by small white patches.

To the right is the curious "flower-bearing" sea-weed known as the

Sea Rose, _Constantinea Rosa marina_, the flower-like growth of

which, combined with the pink colour of its seeming flowers, is very

remarkable.

In front, and rather to the right of the last, is a dark mass of the

splendid _Iridæa Mertensiana_, the dark velvety masses of which, of a

deep crimson colour, are often more than a foot across.

To the right of the last, in the corner, is one of the most beautiful

of the ulvæ, _Ulva fenestrata_, a name which may be popularised as the

"windowed" ulva, in allusion to its extremely perforated character,

the openings being of considerable size, and often separated from

each other only by the slenderest divisions, thus forming a kind of

vegetable lace-work.

[Illustration: A RUSSIAN OFFICIAL ATTENDED BY A SOLDIER COLLECTING ALGÆ

ON THE SHORES OF THE NORTH PACIFIC.]

The largest of indigenous sea-weeds are the _Laminaria saccharina_ and

_digitata_, or the sugary and fingered oar-weeds. Their stout woody

stems, and broad tough glossy leaves of dark olive-green, often twelve

or fourteen feet long, must be familiar to every one who has sojourned

on the coast. When gliding over their submerged groves in a boat, their

great fronds floating like streamers in the water afford the interesting

spectacle of a dense submarine thicket, through whose palm-like tops the

fishes swim in and out, emulating in activity the birds of our forests.

But our native oar-weeds, large as they seem with regard to the other

fuci among which they grow, are mere pygmies when compared with the

gigantic species which occur in the colder seas.

None of the members of this family grow in the tropical waters, but

they extend to the utmost polar limits, and seem to increase in size

and multiplicity of form as they advance to the higher latitudes. The

northern hemisphere has generally different genera from the southern. To

the former belong the gigantic Alarias with their often forty feet long

and several feet broad fronds, the singularly perforated Thalassophyta,

and the far-spreading Nereocystis, which is only found in the Northern

Pacific; while the genera Macrocystis and Lessonia are denizens of the

Southern Ocean.

In the numerous channels and bays of Tierra del Fuego, the enormous and

singular _Macrocystis pyrifera_ is found in such incredible masses as

to excite the astonishment of every traveller. "On every rock," says

Mr. Darwin, perhaps the best observer of nature that ever visited those

dreary regions, and certainly their most poetical describer, "the plant

grows from low-water mark to a great depth, both on the outer coast and

within the channels. I believe, during the voyages of the Adventure

and Beagle, not one rock near the surface was discovered which was not

buoyed by this floating weed. The good service it thus affords to vessels

navigating near this stormy land is evident, and it certainly has saved

many a one from being wrecked. I know few things more surprising than

to see this plant growing and flourishing amidst those great breakers

of the western ocean, which no mass of rock, let it be ever so hard,

can long resist. The stem is round, slimy, and smooth, and seldom has a

diameter of so much as an inch. A few taken together are sufficiently

strong to support the weight of the large loose stones to which in the

inland channels they grow attached; and some of these stones are so

heavy, that when drawn to the surface they can scarcely be lifted into a

boat by one person."

"Captain Cook, in his second voyage says, that 'at Kerguelen's Land

some of this weed is of most enormous length, though the stem is not

much thicker than a man's thumb. I have mentioned that, on some of

these shoals on which it grows, we did not strike ground with a line

of twenty-four fathoms; the depth of water, therefore, must have been

greater. And as this weed does not grow in a perpendicular direction,

but makes a very acute angle with the bottom, and much of it afterwards

spreads many fathoms on the surface of the sea, I am well warranted to

say that some of it grows to the length of sixty fathoms and upwards.'

"Certainly at the Falkland Islands, and about Tierra del Fuego, extensive

beds frequently spring up from ten and fifteen fathoms water. I do

not suppose the stem of any other plant attains so great a length as

360 feet, as stated by Captain Cook. Its geographical range is very

considerable; it is found from the extreme southern islets near Cape

Horn, as far north on the eastern coast as lat. 43°, and on the western

it was tolerably abundant, but far from luxuriant, at Chiloe, in lat.

42°. It may possibly extend a little further northward, but is soon

succeeded by a different species.

"We thus have a range of 15° in latitude, and as Cook, who must have been

well acquainted with the species, found it at Kerguelen's Land, no less

than 140° in longitude.

"The number of living creatures, of all orders, whose existence

intimately depends on the kelp, is wonderful. A large volume might be

written, describing the inhabitants of one of these beds of sea-weed.

Almost every leaf, except those that float on the surface, is so thickly

incrusted with corallines as to be of a white colour. We find exquisitely

delicate structures, some inhabited by simple hydra-like polypi, others

by more organised kinds and beautiful compound ascidiæ. On the flat

surfaces of the leaves, various patelliform shells, trochi, uncovered

mollusks, and some bivalves are attached. Innumerable crustacea frequent

every part of the plant. On shaking the great entangled roots, a pile

of small fish, shells, cuttle-fish, crabs of all orders, sea-eggs,

star-fish, beautiful holothuriæ (some taking the external form of the

nudibranch mollusks), planariæ, and crawling nereidous animals of a

multitude of forms, all fall out together. Often as I recurred to a

branch of the kelp, I never failed to discover animals of new and curious

structure. In Chiloe, where, as I have said, the kelp did not thrive very

well, the numerous shells, corallines, and Crustacea were absent, but

there yet remained a few of the Flustraceæ, and some compound ascidiæ;

the latter, however, were of different species from those in Tierra del

Fuego. We here see the fucus possessing a wider range than the animals

which use it as an abode.

"I can only compare these great aquatic forests of the southern

hemisphere with the terrestrial ones in the intertropical regions. Yet,

if the latter should be destroyed in any country, I do not believe nearly

so many species of animals would perish, as under similar circumstances

would happen with the kelp. Amidst the leaves of this plant numerous

species of fish live, which nowhere else would find food or shelter; with

their destruction the many cormorants, divers, and other fishing-birds,

the otters, seals, and porpoises, would soon perish also; and lastly the

Fuegian savage, the miserable lord of this miserable land, would redouble

his cannibal feast, decrease in numbers, and perhaps cease to exist."

For many a day's sail before reaching Cape Horn, large bundles of the

macrocystis detached by the storm announce to the navigator that he is

approaching the desolate coasts of Tierra del Fuego.

"We succeeded," says Professor Meyen, in his _Reise um die Welt_,

"in getting hold of one of these floating islands, which, amid loud

acclamations, was hauled upon deck by the exertions of five men. It was

quite impossible to disentangle the enormous mass; we could only detach,

to the length of about sixty feet, what we considered to be the chief

stem; the branches were from thirty to forty feet long, and as thick

as the principal trunk from which they sprang. We estimated the total

length of the plant at about two hundred feet; the pear-shaped air

vessels at the basis of the leaves were often six or seven inches long,

and the leaves themselves measured seven or eight feet. On these swimming

fucus-islands lived a vast multitude of various animals; thousands upon

thousands of barnacles and sertulariæ, of crustaceans and annelides.

"The admiration which the gigantic sea-weeds of Tierra del Fuego excited

in our minds equalled that which had been raised by the exuberant

vegetation of the virgin forests of Brazil. One single plant of the

_Macrocystis pyrifera_ would suffice, like one of the mammoth-trees of

those luxuriant woods, to cover a large space of land with its leaf-like

substance. The quantity of small algæ, of sertularias, cellarias, and

other minute animals dwelling on these swimming islands, surpasses in

variety the multitude of parasitical plants bedecking the trees in a

tropical forest. It seems as if, in these desolate and dreary regions,

the generative powers of the planet were solely confined to the gigantic

growth of submarine vegetation."

On the rocky coasts of the Falkland Islands are found no less

astonishing masses of enormous sea-weeds, chiefly belonging to the

genera Macrocystis, Lessonia, and Durvillea. Rent from the rocks to

which they were attached, and cast ashore, they are rolled by the heavy

surf into prodigious vegetable cables, much thicker than a man's body

and several hundred feet long. Many of the rarest and most beautiful

algæ may be here discovered, which have either been wrenched from

inaccessible rocks far out at sea, along with the larger species, or have

attached themselves parasitically to their stems and fronds. Many of

them remind the botanist, by some similarity of form, of the sea-weeds

of his distant home, while others tell him at once that he is far away

in another hemisphere. The gigantic lessonias particularly abound about

these islands. Their growth resembles that of a tree. The stem attains

a height of from eight to ten feet, the thickness of a man's thigh, and

terminates in a crown of leaves two or three feet long, and drooping like

the branches of a weeping-willow. They form large submerged forests, and,

like the thickets of the macrocystis, afford a refuge and a dwelling to

countless sea animals.

A similar abundance of colossal algæ is found in the Northern Pacific,

about the Kurile and Aleutic Islands, and along the deeply indented and

channel-furrowed north-west coast of America.

Thus the _Nereocystis lutkeana_ forms dense forests in Norfolk Bay and

all about Sitcha. Its stem, resembling whipcord, and often above 300

feet long, terminates in a large air-vessel, six or seven feet long, and

crowned with a bunch of dichotomous leaves, each thirty or forty feet in

length. Dr. Mertens assures us that the sea-otter, when fishing, loves

to rest upon the colossal air-vessels of this giant among the sea-weeds,

while the long tenacious stems furnish the rude fishermen of the coast

with excellent tackle. The growth of the nereocystis must be uncommonly

rapid, as it is an annual plant, and consequently develops its whole

gigantic proportions during the course of one brief summer.

Before proceeding to the third chief group of marine plants, the red

sea-weeds, or Rhodosperms, I must mention the enormous fucus banks, or

floating meadows of the Atlantic, which form undoubtedly one of the

greatest wonders of the ocean.

We know that the mighty Gulf Stream, which rolls its indigo-blue floods

from America to the opposite coasts of the Old World, flows partly

southwards in the neighbourhood of Azores, and is ultimately driven

back again to America. In the midst of these circuitous streams, from

22° to 36° N. lat., and from 35° to 65° W. long., extends a sea without

any other currents than those resulting from the temporary action of

the winds. This comparatively tranquil part of the ocean, the surface

of which surpasses at least twenty times that of the British Isles, is

found more or less densely covered with floating masses of _Sargassum

bacciferum_. Often the sea-weed surrounds the ship sailing through these

savannas of the sea, in such quantities as to retard its progress, and

then again hours may pass when not a single fucus appears. While Columbus

was boldly steering through the hitherto unknown fields of the Sargasso

Sea, the fears of his timorous associates were increased by this singular

phenomenon, as they believed they had now reached the bounds of the

navigable ocean, and must inevitably strike against some hidden rock, if

their commander persevered in his audacious course.

It is an interesting fact that the Sargasso Sea affords the most

remarkable example of an aggregation of plants belonging to one single

species. Nowhere else, according to Humboldt, neither in the savannas

of America, nor on the heaths or in the pine forests of Northern Europe,

is such a uniformity of vegetation found as in those boundless maritime

meadows.

"The masses of sea-weeds," says Meyen, "covering so vast an extent

of ocean have ever since the time of Columbus been the object of

astonishment and inquiry. Some navigators believe, that they are driven

together by the Gulf Stream, and that the same species of Sargassum

plentifully occurs in the Mexican Sea; this is however perfectly

erroneous.

"Humboldt was of opinion that this marine plant originally grows on

submarine banks, from which it is torn by various forces; I for my part

have examined many thousands of specimens, and venture to affirm that

they never have been attached to any solid body. Freely floating in the

water, they have developed their young germs, and sent forth on all sides

roots and leaves, both of the same nature."

Thus the Sargassum seems to be the indigenous production of the sea where

it appears, and to have floated there from time immemorial. Its swimming

islands afford an abode and nourishment to a prodigious amount of animal

life. They are generally covered with elegant sertularias, coloured

vorticellas, and other strange forms of marine existence. Various naked

or nudibranchiate mollusks and annelides attach themselves to the fronds,

and afford nourishment to hosts of fishes and crustaceans, the beasts of

prey of this little world.

Similar aggregations of sea-weeds are also met with in the Indian and

Pacific Oceans, in the comparatively tranquil spaces encircled by

rotatory currents. Their rare occurrence on the surface of the sea may

serve as a proof of the restless motion of its waters. Were the ocean not

everywhere intersected by currents, it would most likely be covered with

sea-weeds, opposing serious, if not invincible obstacles to navigation.

The _Red_ sea-weeds, Rhodosperms or Florideæ, are by far the most

numerous in species, and undoubtedly the most beautiful and perfect of

all the algæ. They love neither light nor motion, and generally seek the

shade of larger plants on the perpendicular sides of deep tide-pools

removed from the influences of the tides and gales. They mostly grow

close to low-water mark, and are to be seen only for an hour or two at

the spring-tides, during which, as is well known, the deepest ebbs take

place. To this group belong the wonderfully delicate polysiphonias,

callithamnias, plocamias, and delesserias, whose elegant rosy scarlet

or purple leaves are the amateur's delight, and when laid out on paper

resemble the finest tracery, defying the painter's art to do justice to

their beauty. It likewise numbers among its genera the chalky corallines

and nullipores, which on account of the hardness of their substance were

formerly considered to be polyps, but whose true nature becomes apparent

on examining their internal structure.

The _Chondrus crispus_, or Carrigeen, which grows in such vast quantities

on the coasts of the British Isles, also belongs to the rhodosperms,

though when growing, as it frequently does, in shallow tide-pools,

exposed to full sunlight, its dark purple colour fades into green or

even yellowish white. When boiled it almost entirely dissolves in the

water, and forms on cooling a colourless and almost tasteless jelly,

which of late years has been largely used in medicine as a substitute

for Iceland moss. Similar nutritious gelatines, which also serve for the

manufacture of strong glues, are yielded by other species of rhodosperms,

among others by the _Gracillaria spinosa_ of the Indian Ocean, which the

Salangana (_Hirundo esculenta_), a bird allied to the swallow, is said

principally to use for the construction of her edible nest.

The steep sea-walls along the south coast of Java are clothed to the very

brink with luxuriant woods, and screw-pines strike everywhere their roots

into their precipitous sides, or look down by thousands from the margin

of the rock upon the unruly sea below. The surf of incalculable years has

worn deep caves into the chalk cliffs, and here the Salangana builds her

nest. Where the sea is most agitated whole swarms are observed flying

about, and purposely seeking the thickest wave-foam. From a projecting

cape, on looking down upon the play of waters, may be seen the mouth of

the cave of Gua Rongkop, sometimes completely hidden under the waves, and

then again opening its black recesses, into which the swallows vanish, or

from which they dart forth with the rapidity of lightning. While at some

distance from the coast the blue ocean sleeps in undisturbed repose, it

never ceases to fret and foam against the foot of the mural rocks, where

the most beautiful rainbows glisten in the eternally rising vapours.

Who can explain the instinct which prompts the birds to glue their

nests to the high dark vaults of those deep, and apparently so

inaccessible, caverns? Did they expect to find them a safe retreat from

the persecutions of man? Then surely their hopes were vain, for where is

the refuge to which his insatiable avidity cannot find the way? At the

cavern of Gua-gede, the brink of the precipitous coast lies eighty feet

above the level of the sea at ebb-tide; the wall first bends inwards,

and then, at a height of twenty-five feet from the sea, throws out a

projecting ledge which is of great use to the nest-gatherers, serving

as a support for a rotang ladder let down from the cliff. The roof of

the cavern's mouth lies only ten feet above the sea, which, even at

ebb-tide, completely covers the floor of the cave, while at flood-tide

the opening of the vast marine grotto is entirely closed by every wave

that rolls against it. To penetrate into the interior is thus only

possible at low water, and during very tranquil weather; and even then it

could not be done, if the rugged roof were not perforated and jagged in

every direction. The boldest and strongest of the nest-gatherers wedges

himself firmly in the hollows, or clings to the projecting stones, while

he fastens rotang ropes to them, which then depend four or five feet

from the roof. To the lower ends of these ropes long rotang cables are

attached, so that the whole forms a kind of suspension bridge throughout

the entire length of the cavern, alternately falling and rising with

its inequalities. The cave is 100 feet broad and 150 long as far as

its deepest recesses. If we justly admire the intrepidity of the St.

Kildans, who, let down by a rope from the high level of their rocky

birthplace, remain suspended over a boisterous sea, we must needs also

pay a tribute of praise to the boldness of the Javanese nest-gatherers.

Before preparing their ladders for the plucking of the birds' nests,

they first offer solemn prayers to the goddess of the south-coast, and

sometimes deposit gifts on the tomb where the first discoverer of the

caverns and their treasures is said to repose. Thus in all zones and in

every stage of civilisation, man is directed by an inward voice to seek

the protection of the invisible powers when about to engage in a great

and perilous undertaking.

As I have already mentioned, the Salangana builds her nest of sea-weeds,

which she softens in her stomach and then disgorges. During its

construction new layers, which soon grow hard in the air, are continually

deposited on the margin, until it has attained the proper size. When

gathering time approaches, some of the pluckers daily visit the cavern

to examine the state of the brood. As soon as they find that most of

the young are beginning to be provided with feathers, their operations

commence. These nests form the first quality; those in which the young

are still completely naked, the second; while those which only contain

eggs, and are consequently not yet ripe, rank third. The nests with

young whose feathers are completely developed are over-ripe, black, and

good for nothing. All the young and eggs are thrown into the sea. The

gathering takes place three times a year; the birds breed four times

a year. In spite of these wholesale devastations their numbers do not

diminish; as many of the young have no doubt flown away before the day of

execution, or other swallows from still unexplored caverns may fill up

the void. In this manner about 50 piculs are annually collected, which

the Chinese pay for at the rate of 4000 or 5000 guilders the picul. Each

picul contains on an average 10,000 nests. Dividing these 500,000 nests

among three gatherings, and reckoning two birds to each nest, we find

that more than 333,000 swallows inhabit at the same time the Javanese

coast caverns.

In the interior of the island, in the chalkstone grottos of Bandong, the

Salangana also breeds, but in far inferior numbers, as here the annual

collection amounts on an average to no more than 14,000 nests. In these

inland caves swallows and bats reside together, but without disturbing

each other, as the former when not breeding leave their caverns at

sunrise, disappear in the distance, and only return late in the evening,

when the bats are already enjoying their vespertine or nocturnal flight.

In Sumatra and some other islands of the Indian archipelago, birds'-nests

are likewise collected, but nowhere in such numbers as in Java. They are

brought to the Chinese market, where they are carefully cleaned before

being offered for sale to the consumer. The addition of costly spices

renders them one of the greatest delicacies of Chinese cookery, but as

for themselves they are nothing better than a fine sort of gelatine.

The Japanese have long been aware that these costly birds' nests are

in fact merely softened algæ. They consequently pulverise the proper

species of sea-weeds, which are abundantly found on their own coasts,

boil them to a thick jelly, and bring them to market under the name of

_Dschin-schan_, as artificial birds'-nests. The Dutch call it Agar-agar,

and make great use of it; simple boiling sufficing to convert the dried

substance into a thick uniform jelly, which is both nourishing and easy

of digestion. Thus we see that the algæ, which the Romans considered

so perfectly worthless that, when they wished to express their utter

contempt of an object, they declared it to be still viler than the vile

sea-weed, are by no means deserving of so hard a sentence. Man himself

might be much more justly reproached for neglecting the abundant stores

of nourishment which nature has gratuitously provided for him on all flat

and rocky coasts. For not only the species I have mentioned are eatable,

but also some of the commonest fuci of our seas (_Fucus nodosus_, _F.

vesiculosus_, _Laminaria saccharina_), as well as the gigantic alarias

and durvilleas of the colder oceanic regions. And yet how rare is their

use, notwithstanding the increasing wants of a rapidly growing population!

[Illustration: Surirella constricta.

A. Front view. B. Binary subdivision.--(Highly magnified.)]

Besides the larger forms of vegetation, the ocean contains a vast

number of microscopical plants. Among these the most remarkable are

the Diatomaceæ, simple vegetable cells enclosed in a flinty envelope,

consisting of two plates closely applied to each other like the two

valves of a mussel. The forms of these minute organisms are no less

curious than those of the Foraminifera, for they exhibit regular

mathematical figures, and their surface is often most delicately

sculptured. Multiplying by spontaneous fissure, many of the Diatoms are

met with entirely free after the process of duplicative subdivision

has once been completed, while others, such as the Licmophora, or

Fan-bearer, an elegant native species, habitually remain coherent one to

another, producing clusters or filaments of various shapes, connected

by a gelatinous investment or by a stalk-like appendage, which serves

to attach them to other plants or to stones and to pieces of wood.

Though individually invisible to the naked eye, they appear, when thus

congregated, as patches of a green or brownish slimy mass, or as little

glittering tufts a line or two in height. Some of their numerous species

are natives of fresh water, but by far the majority are denizens of

the sea, where they are found from the equator to the poles. The brown

scum floating upon the surface of the antarctic waters near the mighty

ice barrier which arrested Sir James Ross's progress to the south pole

was found to consist almost solely of Diatomaceæ, and they are equally

abundant in the Arctic Ocean.

It is remarked by Dr. Hooker that the universal presence of this

invisible vegetation throughout the South Polar Seas is a most important

feature, since there is a marked deficiency in this region of higher

forms of vegetation, so that without the Diatoms there would neither be

food for aquatic animals nor (if it were possible for these to maintain

themselves by preying on one another) could the ocean waters be purified

of the carbonic acid which animal respiration would be continually

imparting to it. Thus it is not in vain that they abound in the most

inhospitable seas, where but for them no sea-bird would flap its wings,

and no dolphin dart through the desert waters.

[Illustration: Licmophora flabellata. (Highly magnified.)]

From the indestructible nature of their flinty coverings the Diatoms play

a no less conspicuous part in the geological history of our globe than

the calcareous Foraminifera.

Extensive rocky strata, chains of hills, beds of marl--once deposited

at the bottom of the ocean, and raised by subsequent changes of level

from the depth of the waters--contain the remains of these little

plants in greater or less abundance. No country is destitute of such

monuments, and in some they constitute the leading features in the

structure of the soil. Under the whole city of Richmond, in Virginia,

and far beyond its limits, over an area of unknown extent, they form a

stratum of eighteen feet in thickness, and similar deposits are found

to alternate in the neighbourhood of the Mediterranean with calcareous

strata chiefly composed of Foraminifera. At first sight it may seem a

gross exaggeration to attribute so vast an agency to beings individually

so minute, but when we recollect how quickly they multiply by division,

and how their activity dates from the first dawn of organic creation,

their architectural powers no longer seem incredible. In forty-eight

hours a single diatom may multiply to 8,000,000, and in four days to

140,000,000,000,000, when the silicious coverings of its enormous

progeny will already suffice to fill up a space of two cubic feet. No

wonder, then, that during the course of ages these microscopic plants

have been able to form prodigious strata wherever circumstances favoured

their propagation. In no case is the power of numbers more forcibly

exemplified, for where can we find results more vast, proceeding from

the infinite multiplication of the smallest individuals, than that whole

tracts of country should literally be built up of the skeletons of

Foraminifera and Diatomaceæ?

[Illustration: Hooded Merganser.]

CHAP. XX.

THE GEOGRAPHICAL DISTRIBUTION OF MARINE LIFE.

The Dependence of all created Beings upon Space and Time.--The

Influences which regulate the Distribution of Marine Life.--The

four Bathymetrical Zones of Marine Life on the British Coasts,

according to the late Professor Edward Forbes of Edinburgh.--Abyssal

Animals.--_Bathybius Haeckelii._--Deep-Sea Sponges and

Shell-Fish.--Vivid Phosphorescence of Deep-Sea Animals.--Deep-Sea

Shark Fishery.--The "Challenger."

The wanderer to distant lands sees himself gradually surrounded by a new

world of animals and plants. On crossing the Alps, for instance, the

well-known vegetable forms of our native country leave us one after the

other; the beech, the fir, the oak, no longer meet the eye, or appear

but rarely, and of more stunted growth, while in their stead citron and

olive-trees decorate the landscape; and finally, on the shores of the

Mediterranean the world of palms begins to disclose its beauties.

Thus during a long journey our early companions drop off one after the

other, until at last we see ourselves surrounded by a crowd of new

associates, who were strangers to us at the beginning of our pilgrimage.

We may cross the earth from pole to pole, or follow the sun in his

diurnal course; in all directions, from north to south and from east to

west, Nature will be found to change her garments as we proceed, and

never to resume again those she has once cast off. The plants and animals

of the temperate and cold regions of the north are different from those

of the analogous regions in the southern hemisphere; and in the tropical

zone each part of the world nourishes its peculiar inhabitants.

Similar changes meet our eye on ascending from the plains to the

summits of high mountains. At the foot of Etna flourishes the luxuriant

vegetation of a warmer sky, the palmetto (_Chamærops humilis_) and

the pomegranate, even the cotton shrub and the sugar-cane; higher up,

the cool shade of magnificent chestnut woods refreshes our path; then

follows the stately oak; until finally we attain the dreary height where

all vegetation ceases in the dreadful cold of an eternal winter. With

every thousand feet we rise above the level of the sea, we seem to have

advanced nearer and nearer to the pole.

This wonderful change of form, which decorates the various regions of the

earth with such an endless variety of organised existence, alike prevails

in the realms of ocean. Here we find every larger sea-basin nourishing

its peculiar inhabitants, and discover at various vertical distances

beneath the surface of the sea, changes in organic nature similar to

those we observed at different distances above its level.

Thousands of extinct animal and vegetable forms, which have successively

flourished and disappeared, teach us the important lesson, that all

created beings are made but for a season. It is only during a determined

epoch of planetary life that each genus or species finds that combination

of outward circumstances, under which it is able to attain its highest

perfection. But imperceptibly, in the course of ages, the external world

modifies its nature; families once flourishing in a different atmosphere

decline and wither; they are no longer able to maintain themselves

against new forms of life starting up in all the vigour of youth, and

disappear from the scene, supplanted by races which must one day vanish

in their turn.

Organic life is no less dependent on place than it is on time. Of the

numberless animal and vegetable forms that people the earth, each

finds in only one spot the scene of its greatest size and its greatest

profusion. Some endowed with a more pliable or energetic nature occupy a

large space upon the surface of the globe; we find them in the enjoyment

of healthy existence scattered far and wide over whole hemispheres, while

others are obliged to content themselves with the narrowest birthplace,

and are not seldom confined to a single bay, or a single mountain side.

A great part of the magic charm of nature is owing no doubt to this

deep and mysterious connexion between the soil and its productions.

Here all is harmony; we feel it in our hearts; and our eye delights in

the consonance of forms and colours, as our ear in the concord of sweet

sounds. And where is the mortal artist whose paintings could rival the

ever-changing panorama which the Master of all worlds unfolds through all

zones, from pole to pole? His pictures constantly fade away; but they

are perpetually succeeded by new creations of equal beauty. Happy the

man whose eye is open to their charms! Every ramble through the woods and

fields is to him a banquet of pure and inexhaustible delight.

The causes which confine the life of animals and plants to circumscribed

localities are in many cases easily to be traced. The warmth or coldness

of the sea, resulting from currents, geographical position, and depth;

tranquil or disturbed, pure or troubled waters; abundance or scarcity

of food, solidity or softness of the ground, sufficiently explain why

many species of marine animals appear in some places in considerable

numbers, while in others they are totally wanting. A superficial view of

their organisation often shows us at once the physical properties their

_habitat_ must necessarily possess. By looking at a fucus we immediately

see whether it requires the protection of tranquil waters, or is able to

bid defiance to the floods; whether it is made to anchor upon the rock,

or to sink its roots into a more yielding soil.

In many cases, however, the causes which regulate the distribution of the

sea-animals are still enveloped in darkness, and we no more know why the

tropical seas bring forth in some places numerous coral-reefs, and none

at all in other to all appearance just as favourably situated localities,

than we do why the tea-plant is confined to a small corner of Asia, or

the Peruvian cinchonas to a narrow girdle on the Andes.

Evidently, besides the influences known to us, there are many other

hidden ones at work, whose conflicting powers draw round every living

creature a mysterious circle, whose bounds it is unable to transgress.

Their discovery belongs to the future, and certainly forms one of the

most interesting subjects for the naturalist's inquiries.

The geographical distribution of the terrestrial plants and animals is

undoubtedly much easier to be ascertained than that of the denizens of

the ocean. The naturalist is able to climb the highest mountains beyond

the extreme limit of vegetation, and far above their most towering peaks

his eye, piercing the transparent atmosphere, sees the condor soar in

solitary majesty; he can wander through the deepest glens, or even,

penetrating into the bowels of the earth, examine and collect the forms

of the subterranean flora; but it has not been given him to perambulate

the submarine meads, or to force his way leisurely through dense thickets

of algæ, and explore their hidden wonders.

Yet, in spite of these natural impediments, his inventive genius, fired

by his insatiable avidity of knowledge, has given him the means of

interrogating the abyss, and partly raising the veil behind which marine

life conceals its secret operations. Armed with a dredge, he fetches from

the bottom of the sea plants, polypi, mollusks, and annelides, and learns

to distinguish the various depths assigned for their abode; or he puts on

the helmet of the submarine diver, and passes whole hours in collecting

and observing beneath the clear waters of the sea; or he drops the

plummet hundreds of fathoms deep into the ocean, and draws it up again

coated with specimens of corals or Foraminifera.

To the late Professor Edward Forbes of Edinburgh science is indebted for

the first investigations of this nature that have been undertaken on a

greater scale; and, to give the reader some idea of the causes which

regulate the distribution of marine life, I cannot do better than cite a

few of the general results of that eminent naturalist's researches.[U]

[Footnote U: Natural History of the European Seas, by the late Professor

E. Forbes. Edited by R. Godwin Austen, 1859.]

As the animals and plants of the land are grouped together into distinct

zoological and botanical provinces, so likewise is the population of the

sea gathered into geographical groups, which, though well marked in their

more central and most developed portions, imperceptibly merge at their

margins into those of neighbouring realms. "These submarine provinces

have a more or less direct correspondence with those of the neighbouring

lands, though sometimes they differ very considerably from the latter in

their extent; since the physical features which may constitute boundaries

in the one, may not be sufficiently extended or developed in the other

to impede the spread of peculiar species of animals or plants. Marine

creatures, owing to their organisation and the transporting powers of

the element in which they live, are much more capable of diffusion, as

a whole, than the terrestrial organisms; hence we should expect to find

the regions they respectively inhabit, beneath the waves, of much vaster

dimensions than those occupied by similar geographical assemblages

of their terrestrial brethren; and such is to a great extent true.

Nevertheless, the inequalities of the sea-bed, the modifications of the

temperature of the ocean produced by currents pouring through it like

mighty rivers, the projection of promontories, and the more important

interruptions caused by the great gulfs and abysses of the deep, or by

vast and comparatively desert tracts of unprolific sand, which in many

places are spread out in extensive shallows, are all-powerful influences,

determining their diffusion within certain and more or less defined

limits."

The _structure of the coast_, as far as the mineral character of its

rocks is concerned, may seriously affect the distribution of particular

tribes. Since many shell-fish, for instance, bore only in limestone or

rocks containing abundance of lime, a very ordinary difference in the

nature of the strata must necessarily determine their presence or absence.

The _outline of a coast_ has also great influence in regulating the

diffusion of species. A much indented region is very favourable to

submarine life; a straight coast-line, exposed to the full rolling of the

surf, is usually unfavourable, though there are a few creatures which

delight in the dash of the waves, and hardily, though some of them are

small and exceedingly delicate, brave the full force of the ocean storms,

reminding us, as Mr. Godwin Austen quaintly remarks, "of those sturdy

people, not uncommon in this stormy life, who thrive best in troubles,

and feel happiest under conditions that make most men miserable."

The _nature of the sea-bottom_, according as it consists of mud, sand,

gravel, nullipore, broken shells, loose stones, or rock, determines, to a

great extent, the presence or absence of peculiar forms of shell-fish and

other invertebrata, and of fish also, since the distribution of the food

regulates that of the devourers.

The _rise and fall of the tides_ are most important in determining the

presence or absence of the species inhabiting the littoral zone. The

_currents_, besides their agency as modifiers of climate, act as means

of transport, by carrying the germs and larvæ of numerous creatures from

region to region.

The _influence of climate_ is conspicuously manifested in the diminution

of the number of genera and species as we proceed northwards to the Icy

Ocean.

The _composition of the waters_ has also a most important effect on the

distribution of aquatic animals, as the degree of saltness or freshness

determines the presence or absence of numerous forms of both fishes and

invertebrate animals; and last, not least, the _influence of depth_, in

which _pressure_ and the _diminution of light_ are doubtless important

elements, is everywhere manifest over the ocean, "for everywhere we

find creatures, whether animal or vegetable, distributed in successive

belts or regions, from high-water mark down to the deepest abysses from

which living beings have been drawn up. Peculiar types inhabit each of

the zones, and are confined within their destined limits, whilst others

are common to two or more, and not a few appear capable of braving all

bathymetrical conditions. Nevertheless, so marked is the appearance

of the inhabitants of any given region of depth, that the sight of a

sufficient assemblage of them from any one locality will enable the

naturalist at once to declare the soundings within certain limits, and

without the aid of line or plummet."

In the British seas _four_ distinct and well-marked zones of life succeed

each other in vertical extension. The first of these is the _littoral

zone_, equivalent to the tract between tide-marks, but quite as manifest

in those portions of the coast-line where the tides have a fall of only

a foot or two, or even less, as in districts where the fall is very

great. This important belt, which again forms four subdivisions, and is

inhabited by animals and plants capable of enduring periodical exposure

to the air, to the glare of light, the heat of the sun, the pelting of

rain, and often to being more or less flooded with fresh water when the

tide has receded, claims many genera as well as species peculiar to

itself. "The verge of continual air is generally distinguished by the

abundant presence of _Fucus canaliculatus_, among whose roots may be

found crowds of small varieties of the periwinkle, called _Littorina

rudis_, which indeed range out of the water considerably, and may be

found adhering to rocks many feet above high-water mark." The second

sub-region is marked by the abundance of a small dark rigid sea-weed,

called _Lichina_, painting the rock sides as if with a dingy stripe.

With it we find the larger forms of _Littorina rudis_, abundance of the

common limpet (_Patella vulgata_), the common mussel (_Mytilus edulis_),

and myriads of small seaside barnacles, often striping the sea-wall in

a broad white band. "Where the shore shelves a little, and rocky ledges

decline gradually into the sea, the common mussel delights to live,

firmly anchored by its byssal cable in the crevices of rocks or among

masses of gravel, the pebbles of which are tied together by its silky

filaments." The rock sides and the floors of transparent pools are here

often thickly coated with a nullipore, forming a hard pale red crust.

The region of half-tide forms a third subdivision of the littoral zone,

and is exceedingly prolific in marine animals and plants. "Here we find

_Fucus articulatus_, with its graceful even-edged rich brown fronds,

mingled occasionally with the less elegant _Fucus nodosus_. Here limpets

throng, and dog-periwinkles (_Purpura lapillus_) crawl observantly,

seeking to bore more passive mollusks and extract their juicy substance.

This is the home of the best of periwinkles, the large black _Littorina

littorea_, gathered in thousands for the London market. On our western

coasts we find it in company with the purple-striped top-shell (_Trochus

umbilicatus_), and towards the south with the larger _Trochus crassus_.

Here also sea-anemones love to expand their many-armed disks, often

glowing with the most brilliant colours." A fourth sub-region succeeds,

the lowest belt above low-water mark, and is distinguished by the

presence of the black saw-toothed sea-weed (_Fucus serratus_), so much

used in the packing of lobsters for market. On its fronds creeps the

lowest in grade of the periwinkles, the variously tinted _Littorina

neritoides_, exhibiting every colour in its obtuse and thickened shell.

[Illustration: Limpet.]

[Illustration: Periwinkle.]

"At the verge of low-water mark, immediately below it, wherever the coast

is rocky, there are all round the British shores, within a space of a few

inches, a remarkable series of more or less distinctly defined belts,

each consisting of a different species of sea-weed. These in succession

are, the _Laurencia pinnatifida_ uppermost; then the green _Conferva

rupestris_; then the elegant and firm, often iridescent, fronds of

_Chondrus crispus_; and, lowermost, the thong-weed or _Himanthalia

lorea_."

Succeeding the shore-band, or littoral zone, we have the _region of

the great laminaria or tangle forests_, or in sandy places the waving

meadows of zostera, or grass-wrack. It extends from the edge of low

water to a depth varying in different localities, but seldom exceeding

fifteen fathoms, and is itself divided into sub-regions, marked by

belts of differently tinted algæ. This zone above all others swarms

with life, and is the chief residence of fishes, mollusks, crustaceans,

and invertebrata of all classes, remarkable for brightness and variety

of colouring. "Here," says Mr. Godwin Austen, "is the chosen haunt of

the nudibranchiate mollusks, animals of exceedingly delicate texture,

extraordinary shapes, elegance of organs, and vividness of painting.

Their bodies exhibit hues of a brilliancy and intensity such as can match

the most gorgeous setting of a painter's palette. Vermilion red, intense

crimson, pale rose, golden yellow, luscious orange, rich purple, the

deepest and the brightest blues, even vivid greens and densest blacks,

are common tints, separate or combined, disposed in infinite varieties

of elegant patterns, in this singular tribe. Our handsomest fishes

are congregated here, the wrasses especially, some of which are truly

gorgeous in their painting. Here are gobies and more curious blennies,

swimming playfully among these submarine groves. Strange worms crawl

serpent-like about their roots, and formidable crustacea are the wild

beasts who prowl amid their intricacies. The old stalks, and the surfaces

of the rocky or stony ground on which they usually grow, are incrusted

like the trunks of ancient trees or faces of barren rocks with lichenous

investments. But whereas in the air these living crusts are chiefly if

not all of vegetable origin, in the sea they are more often constructed

out of animal organisms. Some of them are sponges, others are true

zoophytes, others polyzoa or bryozoa, beings that have proved to belong

to the class of mollusks, however unlike they may seem to shell-fish.

"In the middle and lower part of the Laminarian region around our shores

the tangles become less plentiful as we descend, and at last become

exceptional and disappear. But other sea-weeds are very abundant,

especially those that delight in red or purple hues. Tender sea-mosses,

exquisitely delicate in form and colouring, abound. Where none of these

are very plentiful, we often find the coral-weed or nullipore in vast

quantities, and assuming many strange modifications of form. Among these

vegetable corals numbers of shells and articulate animals delight to

live, and probably not a few feed upon their stony fronds. The Lima, a

shell-fish related to the scallop, gathers the broken branches by means

of prehensile tentacles, and constructs for itself a comfortable nest

lined with a woven cloth of byssal threads. Numerous fishes resort to

these rugged pastures in order to deposit their spawn among the gnarled

branchlets."

To the laminarian succeeds the _coralline zone_, extending in most

places some thirty fathoms or more. Plants, indeed, are rare, but here

the horny plant-like sertularias love to rear their graceful feathery

branches, and form miniature gardens of fairy-like delicacy and beauty;

and here carnivorous mollusks, whelks above all, prowl in great numbers.

Bivalves of remarkable elegance, especially clams and scallops, are

found buried in multitudes beneath its gravels and muddy sands; and no

less plentifully congregate the spider-crabs, with many other peculiar

crustaceans. As a natural consequence of this well-furnished table,

fishes abound, and many of our deep sea and white fisheries owe their

value to the zoological features of the coralline zone.

Last and lowest of our regions of submarine existence is that of

_deep-sea corals_, so named on account of the great stony zoophytes

characteristic of it in the oceanic seas of Europe. Many sea-stars and

sea-urchins are likewise found in this region, in the depths of which the

number of peculiar creatures is few, yet sufficient to give it a marked

character.

[Illustration: Whelk.]

[Illustration: Gurnard.]

The aspect of the British submarine fauna is in general more remarkable

for elegance of form and neat simplicity than for glaring or vivid hues.

"The smaller kinds of sponges are not seldom brilliantly dyed, but the

more conspicuous kinds are tawny or brownish. The sea-anemones are

elegantly variegated with rich colours, but the majority of zoophytes are

not strikingly tinted. The star-fishes, as a group, are most remarkable

among the invertebrata for gorgeous painting, but our sea-urchins

are sombre when compared with their relatives from warmer seas. The

jelly-fish are occasionally tinged with delicate hues, and some of the

smaller kinds even showily ornamented; but those which most figure in

our waters are not conspicuous on account of colour, however elegant in

their contours. Our marine shells, though often pretty, are not gaudy or

attractive, except in rare instances. The same may be said with almost

equal truth of our marine crustaceans, though, on close inspection,

the elegance of device on the carapaces of many species is exceedingly

admirable."

Our fishes are not distinguished by brilliancy of colour. "Their hues

are quaker-like, though sufficiently lustrous for sober tinting. The

cod and flounder tribes are among the most characteristic, and such of

the more common fishes as belong to families of which we have but few

representatives are in most instances clothed in sober grey and silver.

Beauty of no mean description may, however, be displayed by these modest

vestments; as, for instance, in the mackerel and the herring. Our

gorgeously decorated wrasses form the chief exception to the general

rule, but these belong to a family more characteristic of the southern

seas. A like deficiency in the numbers of the gurnard and mackerel tribes

seriously affects the aspect of our piscine fauna when compared with

denizens of the Mediterranean." The sharks and rays too are comparatively

deficient, although a few species, as we have seen in a former chapter,

are, to the great annoyance of our fishermen, over-abundant. The sea-eels

are also few, though in the common conger and the larger sand-eel

(_Ammodytes lancea_) we have two very conspicuous species.

[Illustration: Sand-Eel.]

[Illustration: Grey Mullet.]

[Illustration: Red Mullet.]

[Illustration: Salmon.]

As the surface of the British islands exhibits a transition as it were

from a northern to a southern character, from the firs of Scotland to the

free-growing myrtles of the Devon coast, so the inhabitants of our seas

pass through a great variety of form, from a northern to a southern type.

While the rorqual of the Frozen Ocean not seldom strands on our northern

and eastern coasts; the flying-fish of the equinoctial seas sometimes

appears within view of our southern shores; and it is this peculiar

position of our insular empire, fronting the colder and the warmer seas,

which enriches its waters with such a variety of marine life. "Several

characteristic boreal forms find their southern limit within the northern

half of our waters, and there some of the most striking and abundant

kinds are chiefly developed in numbers, such as the cat-fish or sea-wolf

(_Anarhicas lupus_), the scythe (_Merlangus carbonarius_), the ling

(_Lota molva_), the cod (_Gadus morrhua_), the lump-sucker (_Cyclopterus

lumpus_), and even the herring (_Clupea harengus_). On the other hand,

along the southern shores of England we find fishes becoming frequent

which are distinctly of a southern type, such as the grey and red mullets

(_Mugil cephalus_ and _Mullus barbatus_), the sea-bream, and, far more

plentifully, the John Dory (_Zeus aper_) and the pilchard (_Clupea

pilchardus_)."[V]

[Footnote V: Godwin Austen, Natural History of the European Seas, pp.

103, 104.]

Although very inferior in beauty to the tropical fishes, our finny

tribes are far superior in flavour, and may well challenge the world to

produce their equals for the table. The turbot, cod, whiting, herring,

whitebait, mackerel, sole, and even the salmon, though it belongs rather

to fluviatile history than to the chronicles of the sea, may fairly be

cited to testify to the truth of this assertion; so that surely we have

no reason to complain of having been but indifferently provided for in

the geographical distribution of fishes, which of all marine productions

are the most important to man.

The researches of Forbes led him to believe that "as we descend deeper

and deeper, the denizens of the sea become fewer and fewer, indicating

our approach towards a silent and desolate abyss, where life is either

extinguished or exhibits but faint glimmerings to mark its lingering

presence;" but subsequent deep-sea soundings, performed with improved

dredging apparatuses, have led to the surprising result that the bottom

of the ocean, even in its abyssal depths, far from being a dreary void,

as was formerly imagined, is in reality a busy scene, absolutely teeming

with life. And in this case, as in so many others, we have a fine

instance of the truth of the observation that every new invention or

discovery casts a new light upon some other province of human knowledge;

for to the submarine telegraph we are indebted for the first certain

proof of the existence of highly organised animals living at abyssal

depths.

In 1860 the submarine cable between Sardinia and Bona, on the coast of

Africa, having completely failed, was picked up from a depth exceeding

one thousand fathoms, and found encrusted with various shells and corals.

All previous observations with reference to the existence of living

creatures at extreme depths had been liable to doubt from two sources. In

the first place the methods of deep-sea soundings were still so imperfect

that there was always a possibility, from the action of deep currents

upon the sounding-line or from other causes, of a greater depth being

indicated than really existed; and, secondly, there was no absolute

certainty that the animals entangled on the sounding instrument had

actually come up from the bottom. They might have been caught on the way.

But now all doubt was removed. A submarine cable lies on the ground

throughout its whole length. Before laying it, its course is carefully

surveyed and the real depth accurately ascertained. Fishing it up is a

delicate and difficult operation, and during its progress the depth is

checked again and again. When, therefore, as in this case, the animals

dragged up with a cable from depths of upwards of one thousand fathoms

are found, not sticking loosely to it, but moulded upon its outer

surface, or cemented to it by horny or calcareous excretions, it is

evident that they must have lived and grown upon it at the bottom of the

deep sea.

The subsequent dredging cruises of H.M.SS. "Porcupine" and "Lightning" in

1868, 1869, and 1870, under the scientific direction of Dr. Carpenter,

Professor Wyville Thomson, and Mr. Gwyn Jeffreys, afforded additional

and convincing proofs that life abounds in the abyssal regions of the

ocean. During these several cruises 57 hauls of the dredge were taken at

depths beyond 500 fathoms, and 16 at depths beyond 1,000 fathoms, and

in all cases life was abundant. In 1869 two casts were taken in depths

greater than 2,000 fathoms, and proved equally successful in bringing up

specimens of deep-sea life. With the deepest cast, 2,435 fathoms, off

the mouth of the Bay of Biscay, living, well-marked, and characteristic

specimens of all the five invertebrate sub-kingdoms were taken. "And

thus," says Professor Wyville Thomson,[W] "the question of the existence

of abundant animal life at the bottom of the sea has been finally

settled, and for all depths, for there is no reason to suppose that the

depth anywhere exceeds between three and four thousand fathoms; and if

there be nothing in the conditions of a depth of 2,500 fathoms to prevent

the full development of a varied fauna, it is impossible to suppose that

even an additional 1,000 fathoms would make any great difference."

[Footnote W: The Depths of the Sea. London, 1873.]

It may be asked how the deep-sea animals bear the enormous pressure at

these great depths, which seems at first sight alone sufficient to put

any idea of life out of the question? There was a curious popular notion

that on descending deeper and deeper the sea water became gradually,

under the pressure, heavier and heavier, so that at last it became more

weighty than molten gold. But water is, in fact, almost incompressible;

so that its density at 2,000 fathoms is scarcely appreciably increased.

Any free air suspended in the water, or contained in any compressible

tissue of an animal at 2,000 fathoms, would of course be reduced to a

mere fraction of its bulk; but the animals subject to the pressure of

the deep seas, being permeated throughout their whole organisation by

incompressible fluids at the same pressure, are consequently as capable

of bearing it as we do the pressure of the atmosphere. The absence of

light seemed another circumstance incompatible with the existence of

animal life at abyssal depths, as all plants depend upon light for

their growth, and their absence apparently involves that of vegetable

food, which, as we all know, forms everywhere the substratum of animal

existence. We have as yet very little exact knowledge as to the distance

to which the sun's light penetrates into the water of the sea. According

to some recent experiments it would appear that the rays capable of

affecting a delicate photographic film are very rapidly cut off, their

effect being imperceptible at the depth of only a few fathoms; and though

probably some portions of the sun's light possessing certain properties

may penetrate to a much greater distance, it is certain that, beyond the

first fifty fathoms, plants to whose existence light is essential are

barely represented, and after two hundred fathoms entirely absent.

But though plant-life is thus limited to the more superficial parts of

the ocean, the analysis of sea water, taken in all localities and at all

depths, has shown that it everywhere contains a very appreciable and very

uniform quantity of organic matter in solution and in suspension. It

is thus quite intelligible that numberless protozoa--whose distinctive

character is that they are capable of being supported by the absorption

of organic matter through the surface of their bodies--are able to exist

in the dark abysses of the sea, and in their turn afford nourishment to

more highly organised animals.

After these general remarks on the creatures of the deep, I will now give

a brief account of their various groups.

Over an enormous extent the abyssal ocean bottom is found covered with a

sheet of almost formless beings, absolutely devoid of internal structure,

and consisting merely of living and moving expansions of jelly-like

matter. Whether this form of life, still more simple than the Amœba,[X]

to which Professor Huxley has given the name of _Bathybius Haeckelii_, be

continuous in one vast sheet or broken up into circumscribed individual

particles, it is equally an object of wonder; and as no living thing,

however slowly it may live, is ever perfectly at rest, it shows us that

the bottom of the sea is, like its surface, the theatre of perpetual

change.

[Footnote X: See Chapter XVIII., p. 380.]

Living among and upon this Bathybius we find a multitude of other

protozoa, foraminifera and other rhizopods, radiolarians, and sponges.

Such is the countless number of the Foraminifera inhabiting the deep

seas, that their remains form the chief mass of the soft oozy bottom of

the ocean. In the surface layer of the deposit the shells of _Globigerina

bulloides_, the prevailing species, are found fresh, whole, and living,

and in the lower layers dead and gradually crumbling down by the

decomposition of their organic cement and by the pressure of the layers

above. Countless generations are thus piled one upon the other; and each

successive stratum, weighing upon those of older date, is laying the

foundation of future rocks, which subsequent revolutions may perhaps

heave out of the deep and raise in towering pinnacles to the skies.

Sponges[Y] of wonderful beauty and lustre appear to extend in endless

variety over the whole of the bottom of the sea. Some (_Holtenia

Carpenteri_) anchor in the ooze by means of a perfect maze of delicate

glassy filaments, like fine white hair, spreading out in all directions

through the sea's fluid mud; while others (_Hyalonema_) send right down

a coiled whisp of strong spicules, each as thick as a knitting-needle,

which open out into a brush as the bed gets firmer, and fix the sponge

in its place somewhat on the principle of a screw-pile. "A very singular

sponge, from deep water off the Loffoden Islands, spreads into a thin

circular cake, and adds to its surface by sending out a flat border of

silky spicules, like a fringe of white floss silk round a little yellow

mat; and the lovely Euplectella, whose beauty is imbedded up to its

fretted lid in the grey mud of the seas of the Philippines, is supported

by a frill of spicules standing up round it like Queen Elizabeth's

ruff."[Z]

[Footnote Y: Ibid. pp. 385-389.]

[Footnote Z: The Depths of the Sea, p. 73.]

The stalked sea-stars, which, as the fossil pentacrinites and encrinites

testify, abounded in the past periods of the earth's history, were, until

now, supposed to be on the verge of extinction; but when we consider

that the first few scrapes of the dredge at great depths have brought

new species to light, we are entitled to believe that they constitute an

important element in the abyssal fauna, and probably pave large tracts

of the sea-bottom with a carpet of animated flowers. Freely-moving

sea-stars and sea-urchins have likewise been hauled up in great numbers

from abyssal depths; crustaceans have not been found wanting, and the

captured shell-fish have shown that the deep-sea molluscs are by no means

deficient in colour, though as a rule they are paler than those from

shallow water.

_Dacrydium vitreum_, dredged from 2,435 fathoms, a curious little

mytiloïd shell-fish, which makes and inhabits a delicate flask-shaped

tube of foraminifera and other foreign bodies cemented together

by organic matter and lined by a delicate membrane, is of a fine

reddish-brown colour dashed with green, and the animals of one or two

species of Lima from extreme depths are of the usual vivid orange scarlet.

Some of the abyssal molluscs have even been found provided with organs

of sight. A new species of Pleurotoma, from 2,090 fathoms, had a pair

of well-developed eyes on short foot-stalks, and a Fusus from 1,207

fathoms was similarly provided. The presence of organs of sight at these

great depths leaves little room to doubt that light must reach even

these abysses from some source, and as from many considerations it can

scarcely be sunlight, Professor Wyville Thomson throws out the suggestion

"that the whole of the light beyond a certain depth may be due to

phosphorescence, which is certainly very general, particularly among the

larvæ and young of deep-sea animals."

Thus many of the creatures dredged in the Northern Atlantic, off the

west coast of Ireland,[AA] in depths varying from 557 to 584 fathoms,

were most brilliantly phosphorescent. In some places nearly everything

brought up seemed to emit light, and the mud itself was perfectly

full of luminous specks. The alcyonarians, the brittle-stars, and

some annelids were the most brilliant. The Pennatidæ, the Virgulariæ,

and the Gorgoniæ shone with a lambent white light, so bright that it

showed quite distinctly the hour on a watch, while the light from

_Ophiacantha spinulosa_ was of a brilliant green, coruscating from the

centre of the disk, now along one arm, now along another, and sometimes

vividly illuminating the whole outline of the star-fish. While the

Ophiacantha shines like a star of the most vivid uranium green, the

sea-pen (_Pavonaria quadrangularis_) is resplendent with a pale lilac

phosphorescence like the flame of cyanogen gas, not scintillating like

the green light of Ophiacantha, but almost constant, sometimes flashing

out at one point more vividly, and then dying gradually into comparative

dimness, but still sufficiently bright to make every portion of the polyp

visible.

[Footnote AA: Ibid., Chapter III. Cruise of the "Porcupine," pp. 98-149.]

Such numbers of the Pavonaria were brought up at one haul of the dredge

in the Sound of Skye, that the "Porcupine" had evidently passed over a

forest of them. While the darkness of winter frowns over the surface

of the Northern Atlantic, the animated shrubs at its bottom are thus

glowing with light, and a kind of magical day prevails in depths which

were supposed to be shrouded with perpetual night. But it might have been

better for many of the luminous denizens of the abyss if a more obscure

existence had been their lot; for in a sea swarming with predaceous

crustaceans with great bright eyes phosphorescence must surely be a fatal

gift.

Off the coast of Portugal there is a great fishery of sharks

(_Centroscymnus Cœlolepis_), carried on at a depth of 500 fathoms. If an

animal so highly organised as a shark can thus bear without inconvenience

the enormous pressure of more than half a ton on the square inch existing

at that depth, it is a sufficient proof that the pressure is applied

under circumstances which prevent its affecting it to its prejudice,

and there seems to be no reason why it should not tolerate equally well

a pressure of one or two tons, or why many other fishes--though the

dredge, in consequence of their facility of locomotion, will hardly ever

be able to bring them to light--should not abound in the still waters of

the abyssal deep.

The "Challenger" Exploring Expedition will no doubt reveal to us still

many an unknown wonder of those interesting regions, and make us

acquainted with a world of new animals which even the profundity of the

ocean vainly strives to hide from the curiosity of man.

[Illustration]

CHAP. XXI.

THE PHOSPHORESCENCE OF THE SEA.

Its Causes.--Noctiluca miliaris.--Phosphorescent Annelides and

Beroës.--Intense Phosphorescence of the Pyrosoma atlantica.--Luminous

Pholades.--The luminous Shark.--Phosphorescent Algæ.--Citations from

Byron, Coleridge, and Crabbe.

He who still lingers on the shore after the shades of evening have

descended, not seldom enjoys a most magnificent spectacle; for lucid

flashes burst from the bosom of the waters, as if the sea were anxious

to restore to the darkened heavens the light it had received from them

during the day. On approaching the margin of the rising flood to examine

more closely the sparkling of the breaking wave, the spreading waters

seem to cover the beach with a sheet of fire. Each footstep over the

moist sands elicits luminous star-like points, and a splash in the water

resembles the awakening of slumbering flames.

The same wonderful and beauteous aspect frequently gladdens the eye of

the navigator who ploughs his way through the wide deserts of ocean,

particularly if his course leads him through the tropical seas.

"When a vessel," says Humboldt, "driven along by a fresh wind, divides

the foaming waters, one never wearies of the lovely spectacle their

agitation affords; for, whenever a wave makes the ship incline sideways,

bluish or reddish flames seem to shoot upwards from the keel. Beautiful

beyond description is the sight of a troop of dolphins gambolling in the

phosphorescent sea. Every furrow they draw through the waters is marked

by streaks of intense light. In the Gulf of Cariaco, between Cumana and

the peninsula of Maniquarez, this scene has often delighted me for hours."

But even in the colder oceanic regions the brilliant phenomenon appears

from time to time in its full glory. During a dark and stormy September

night, on the way from the Sea-lion island, Saint George, to Unalaschka,

Chamisso admired as beautiful a phosphorescence of the ocean as he

had ever witnessed in the tropical seas. Sparks of light, remaining

attached to the sails that had been wetted by the spray, continued to

glow in another element. Near the south point of Kamtschatka, at a

water-temperature hardly above freezing point, Ermann saw the sea no less

luminous than during a seven months' sojourn in the tropical ocean. This

distinguished traveller positively denies that warmth decidedly favours

the luminosity of the sea.

At Cape Colborn, one of the desolate promontories of the desolate

Victoria Land, the phosphoric gleaming of the waves on the 6th September,

when darkness closed in, was so intense that Simpson assures us he had

seldom seen anything more brilliant. The boats seemed to cleave a flood

of molten silver, and the spray dashed from their bows, before the fresh

breeze, fell back in glittering showers into the deep.

Mr. Charles Darwin paints in vivid colours the magnificent spectacle

presented by the sea, while sailing in the latitudes of Cape Horn on a

very dark night.

There was a fresh breeze, and every part of the surface, which during

the day is seen as foam, now glowed with a pale light. The vessel drove

before her bows two billows of liquid phosphorus, and in her wake she was

followed by a milky train. As far as the eye reached, the crest of every

wave was bright, and the sky above the horizon, from the reflected glare

of these livid flames, was not so utterly obscure as over the rest of the

heavens.

While "La Venus" was at anchor before Simon's Town, the breaking of the

waves produced so strong a light that the room in which the naturalists

of the expedition were seated was illumined as by sudden flashes of

lightning. Although more than fifty paces from the beach where the

phenomenon took place, they tried to read by this wondrous oceanic light,

but the successive glimpses were of too short duration to gratify their

wishes.

Thus we see the same nocturnal splendour which shines forth in the

tropical seas, and gleams along our shores, burst forth from the arctic

waters, and from the waves that bathe the southern promontories of the

old and the new worlds.

But what is the cause of the beautiful phenomenon so widely spread over

the face of ocean? How comes it that at certain times flames issue from

the bosom of an element generally so hostile to their appearance?

Without troubling the reader with the groundless surmises of ancient

naturalists, or repeating the useless tales of the past, I shall at

once place myself with him on the stage of our actual knowledge of this

interesting and mysterious subject. It is now no longer a matter of doubt

that many of the inferior marine animals possess the faculty of secreting

a luminous matter, and thus adding their mite to the grand phenomenon.

When we consider their countless multitudes, we shall no longer wonder

at such magnificent effects being produced by creatures individually so

insignificant.

[Illustration: Noctiluca miliaris. (Highly magnified.)]

In our seas it is chiefly a minute gelatinous animal, the _Noctiluca

miliaris_, most probably an aberrant member of the infusorial group,

which, as it were, repeats the splendid spectacle of the starry heavens

on the surface of the ocean. In form it is nearly globular, presenting

on one side a groove, from the anterior extremity of which issues a

peculiar curved stalk or appendage, marked by transverse lines, which

might seem to be made use of as an organ of locomotion. Near the base

of this tentacle is placed the mouth, which passes into a dilatable

digestive cavity, leading, according to Mr. Huxley, to a distinct

anal orifice. From the rather firm external coat proceed thread-like

prolongations through the softer mass of the body, so as to divide it

into irregular chambers. This little creature, which is just large enough

to be discerned by the naked eye when the water in which it may be

swimming is contained in a glass jar exposed to the light, seems to feed

on diatoms, as their loricæ may frequently be detected in its interior.

It multiplies by spontaneous fission, and the rapidity of this process

may be inferred from the immensity of its numbers. A single bucket of

luminous sea-water will often contain thousands, while for miles and

miles every wave breaking on the shore expands in a sheet of living

flame. It was first described by Forster in the Pacific Ocean; it occurs

on all the shores of the Atlantic, and the Polar Seas are illuminated by

its fairy light. "The nature of its luminosity," says Dr. Carpenter, "is

found by microscopic examination to be very peculiar; for what appears to

the eye to be a uniform glow is resolvable under a sufficient magnifying

power into a multitude of evanescent scintillations, and these are given

forth with increased intensity whenever the body of the animal receives

any mechanical shock."

The power of emitting a phosphorescent light is widely diffused both

among the free-swimming and the sessile Cœlenterata. Many of the

Physophoridæ are remarkable for its manifestation, and a great number of

the jelly-fishes are luminous. Our own _Thaumantias lucifera_, a small

and by no means rare medusid, displays the phenomenon in a very beautiful

manner, for, when irritated by contact of fresh water, it marks its

position by a vivid circlet of tiny stars, each shining from the base of

a tentacle. A remarkable greenish light, like that of burning silver,

may also be seen to glow from many of our Sertularians, becoming much

brighter under various modes of excitation.

Among the Ctenophora the large _Cestum Veneris_ of the Mediterranean is

specially distinguished for its luminosity, and while moving beneath the

surface of the water gleams at night like a brilliant band of flame.

The Sea-pens are eminently phosphorescent, shining at night with a

golden-green light of a most wonderful softness. When touched, every

branchlet above the shock emits a phosphoric glow, while all the polyps

beneath remain in darkness. When thrown into fresh water or alcohol, they

scatter sparks about in all directions, a most beautiful sight; dying, as

it were, in a halo of glory.

But of all the marine animals the Pyrosomas, doing full justice to their

name (fire-bodies) seem to emit the most vivid coruscations. Bibra

relates in his "Travels to Chili" that he once caught half a dozen

of these remarkable light-bearers, by whose phosphorescence he could

distinctly read their own description in a naturalist's vade-mecum.

Although completely dark when at rest the slightest touch sufficed to

elicit their clear blue-green light. During a voyage to India, Mr.

Bennett had occasion to admire the magnificent spectacle afforded

by whole shoals of Pyrosomas. The ship, proceeding at a rapid rate,

continued during an entire night to pass through distinct but extensive

fields of these molluscs, floating and glowing as they floated on all

sides of her course. Enveloped in a flame of bright phosphorescent

light, and gleaming with a greenish lustre, the Pyrosomes, in vast

sheets, upwards of a mile in breadth, and stretching out till lost in the

distance, presented a sight, the glory of which may be easily imagined.

The vessel, as it cleaved the gleaming mass, threw up strong flashes of

light, as if ploughing through liquid fire, which illuminated the hull,

the sails, and the ropes, with a strange unearthly radiance.

In his memoir on the Pyrosoma, M. Péron describes with lively colours

the circumstances under which he first made its discovery, during a

dark and stormy night, in the tropical Atlantic. "The sky," says this

distinguished naturalist, "was on all sides loaded with heavy clouds;

all around the obscurity was profound; the wind blew violently, and the

ship cut her way with rapidity. Suddenly we discovered at some distance

a great phosphorescent band stretched across the waves, and occupying

an immense tract in advance of the ship. Heightened by the surrounding

circumstances, the effect of this spectacle was romantic, imposing,

sublime, rivetting the attention of all on board. Soon we reached the

illuminated tract, and perceived that the prodigious brightness was

certainly and only attributable to the presence of an innumerable

multitude of largish animals floating with the waves. From their swimming

at different depths they took apparently different forms: those at the

greatest depth were very indefinite, presenting much the appearance

of great masses of fire, or rather of enormous red-hot cannon balls;

whilst those more distinctly seen near the surface perfectly resembled

incandescent cylinders of iron.

"Taken from the water, these animals entirely resembled each other in

form, colour, substance, and the property of phosphorescence, differing

only in their sizes, which varied from three to seven inches. The

large, longish tubercles with which the exterior of the Pyrosomes was

bristled were of a firmer substance, and more transparent than the rest

of the body, and were brilliant and polished like diamonds. These were

the principal scene of phosphorescence. Between these large tubercles,

smaller ones, shorter and more obtuse, could be distinguished; these

also were phosphorescent. Lastly, in the interior of the substance of

the animal, could be seen, by the aid of the transparency, a number of

little, elongated, narrow bodies (viscera), which also participated in a

high degree in the possession of the phosphoric light."

In the Pholades or Lithodomes, that bore their dwellings in the hard

stone, as other shell-fish do in the loose sands, the whole mass

of the body is permeated with light. Pliny gives us a short but

animated description of the phenomenon in the edible date-shell of the

Mediterranean (_Pholas dactylus_):--

"It is in the nature of the pholades to shine in the darkness with

their own light, which is the more intense as the animal is more juicy.

While eating them, they shine in the mouth and on the hands, nay, even

the drops falling from them upon the ground continue to emit light, a

sure proof that the luminosity we admire in them is associated with

their juice." Milne-Edwards found this observation perfectly correct,

for wishing to place some living pholades in alcohol, he saw a luminous

matter exude from their bodies, which on account of its weight sank

in the liquid, covering the bottom of the vessel, and there forming a

deposit as shining as when it was in contact with the air.

Several kinds of fishes likewise possess the luminous faculty. The

sun-fish, that strange deformity, emits a phosphoric gleam; and a species

of Gurnard (_Trigla lucerna_) is said to sparkle in the night, so as to

form fiery streams through the water.

[Illustration: Short Sun-Fish.]

With regard to the luminosity of the larger marine animals, Ermann,

however, remarks that he so often saw small luminous crustacea in the

abdominal cavity of the transparent _Salpa pinnata_, that it may well

be asked whether the phosphorescence of the larger creatures is not in

reality owing to that of their smaller companions.

According to Mr. Bennett, "Whaling Voyage round the Globe," a species

of shark first discovered by himself is distinguished by an uncommonly

strong emission of light. When the specimen, taken at night, was removed

into a dark apartment, it afforded a very interesting spectacle. The

entire inferior surface of the body and head emitted a vivid and greenish

phosphorescent gleam, imparting to the creature by its own light a truly

ghastly and terrific appearance. The luminous effect was constant, and

not perceptibly increased by agitation or friction. When the shark

expired, (which was not until it had been out of the water more than

three hours,) the luminous appearance faded entirely from the abdomen,

and more gradually from other parts; lingering longest around the jaws

and on the fins.

The only part of the under surface of the animal which was free from

luminosity was the black collar round the throat; and while the inferior

surface of the pectoral, anal, and caudal fins shone with splendour,

their superior surface (including the upper lobe of the tail fin) was in

darkness, as were also the dorsal fins, and the back and summit of the

head.

Mr. Bennett is inclined to believe that the luminous power of this

shark resides in a peculiar secretion from the skin. It was his first

impression that the fish had accidentally contracted some phosphorescent

matter from the sea, or from the net in which it was captured; but the

most rigid investigation did not confirm this suspicion, while the

uniformity with which the luminous gleam occupied certain portions of the

body and fins, its permanence during life, and decline and cessation upon

the approach and occurrence of death, did not leave a doubt in his mind

but that it was a vital principle essential to the economy of the animal.

The small size of the fins would appear to denote that this fish is not

active in swimming; and, since it is highly predaceous and evidently of

nocturnal habits, we may perhaps indulge in the hypothesis, that the

phosphorescent power it possesses is of use to attract its prey, upon the

same principle as the Polynesian islanders and others employ torches in

night-fishing.

Some of the lower sea-plants also appear to be luminous. Thus, over a

space of more than 600 miles (between lat. 8° N. and 2° S.), Meyen saw

the ocean covered with phosphorescent Oscillatoria, grouped together

into small balls or globules, from the size of a poppy-seed to that of a

lentil.

But if the luminosity of the ocean generally proceeds from living

creatures, it sometimes also arises from putrefying organic fibres

and membranes, resulting from the decomposition of those living

light-bearers. "Sometimes," says Humboldt, "even a high magnifying power

is unable to discover any animals in the phosphorescent water, and yet

light gleams forth wherever a wave strikes against a hard body and

dissolves in foam. The cause of this phenomenon lies then most likely in

the putrefying fibres of dead mollusks, which are mixed with the waters

in countless numbers."

Summing up the foregoing in a few words, it is thus an indisputable fact,

that the phosphorescence of the sea is by no means an electrical or

magnetic property of the water, but exclusively bound to organic matter,

living or dead. But although thus much has been ascertained, we have as

yet only advanced one step towards the unravelling of the mystery, and

its proximate cause remains an open question. Unfortunately, science

is still unable to give a positive answer, and we are obliged to be

contented with a more or less plausible hypothesis. When we consider that

the phosphorescence most commonly resides only in the outward mucous

covering of the body, in which a number of particles cast off by the skin

are continually undergoing decomposition, the phenomenon seems to be a

simple chemical process, during which more or less phosphorus may be

disengaged, which by agitation or friction gives rise to the emission of

light. It is more difficult to explain those cases in which the entire

mass of the body is luminous (as in Pholas), or the muscular substance

(as in some Annelides), or the vibratory cilia (as in the Beroës); and

here we do better to confess our entire ignorance, than to resort to the

hypothesis of electrical discharges, extremely improbable in an element

which is so excellent an electrical conductor, and particularly when we

consider that no emission of light takes place in the few and powerful

electrical fishes we are acquainted with.

We know as little of what utility marine phosphorescence may be. Why do

the countless myriads of Mammariæ gleam and sparkle along our coasts? Is

it to signify their presence to other animals, and direct them to the

spot where they may find abundance of food? So much is certain, that so

grand and wide-spread a phenomenon must necessarily serve some end equally

grand and important.

As the phosphorescence of the sea is owing to living creatures, it must

naturally show itself in its greatest brilliancy when the ocean is at

rest; for during the daytime we find the surface of the waters most

peopled with various animals when only a slight zephyr glides over the

sea. In stormy weather, the fragile or gelatinous world of the lower

marine creatures generally seeks a greater depth, until the elementary

strife has ceased, when it again loves to sport in the warmer or more

cheerful superficial waters.

In the tropical zone, Humboldt saw the sea most brilliantly luminous

before a storm, when the air was sultry, and the sky covered with clouds.

In the North Sea we observe the phenomenon most commonly during fine

tranquil autumnal nights; but it may be seen at every season of the year,

even when the cold is most intense. Its appearance is, however, extremely

capricious; for, under seemingly unaltered circumstances, the sea may one

night be very luminous, and the next quite dark. Often months, or even

years, pass by without witnessing it in full perfection. Does this result

from a peculiar state of the atmosphere, or do the little animals love to

migrate from one part of the coast to another?

It is remarkable that the ancients should have taken so little notice of

oceanic phosphorescence. The "Periplus" of Hanno contains perhaps the

only passage in which the phenomenon is described. To the south of Cerne

the Carthaginian navigator saw the sea burn, as it were, with streams

of fire. Pliny, in whom the miracle (_miraculum_, as he calls it) of

the date-shell excited so lively an admiration, and who must often have

seen the sea gleam with phosphoric light, as the passage proves where he

mentions in a few dry words the luminous gurnard (_lucerna_) stretching

out a fiery tongue, has no exclamation of delight for one of the most

beautiful sights in nature. Homer also, who has given us so many charming

descriptions of the sea in its ever-changing aspects, and who so often

leads us with long-suffering Ulysses through the nocturnal floods, never

once makes them blaze or sparkle in his immortal hexameters.

Even modern poets mention the phenomenon but rarely. Camoens himself,

whom Humboldt, on account of his beautiful oceanic descriptions, calls,

above all others, the "poet of the sea," forgets to sing it in his

Lusiad. Byron in his "Corsair" has a few lines on the subject:

"Flash'd the dipt oars, and, sparkling with the stroke,

Around the waves phosphoric brightness broke;"

but contents himself, as we see, with coldly mentioning a phenomenon so

worthy of all a poet's enthusiasm. In Coleridge's wondrous ballad of

"The ancient Mariner" we find a warmer description:

"Beyond the shadow of the ship

I watch'd the water-snakes:

They moved in tracks of shining white,

And, when they rear'd, the elfish light

Fell off in hoary flakes.

"Within the shadow of the ship

I watch'd their rich attire--

Blue, glossy green, and velvet black:

They coiled and swam, and every track

Was a flash of golden fire."

These indeed are lines whose brilliancy emulates the splendour of the

phenomenon they depict, but even they are hardly more beautiful than

Crabbe's admirable description:

"And now your view upon the ocean turn,

And there the splendour of the waves discern;

Cast but a stone, or strike them with an oar,

And you shall flames within the deep explore;

Or scoop the stream phosphoric as you stand,

And the cold flames shall flash along your hand;

When, lost in wonder, you shall walk and gaze

On weeds that sparkle, and on waves that blaze."

Or than the graphic numbers of Sir Walter Scott:

"Awak'd before the rushing prow,

The mimic fires of ocean glow,

Those lightnings of the wave;

Wild sparkles crest the broken tides.

And flashing round, the vessel's sides

With elfish lustre lave;

While, far behind, their livid light

To the dark billows of the night

A blooming splendour gave."

CHAP. XXII.

THE PRIMITIVE OCEAN.

The Giant-Book of the Earth-rind.--The Sea of Fire.--Formation of a

solid Earth-crust by cooling.--The Primitive Waters.--First awakening

of Life in the Bosom of the Ocean.--The Reign of the Saurians.--The

future Ocean.

The greatest of all histories, traced in mighty characters by the

Almighty himself, is that of the earth-rind. The leaves of this giant

volume are the strata which have been successively deposited in the

bosom of the sea, or raised by volcanic powers from the depths of the

earth; the wars which it relates are the Titanic conflicts of two hostile

elements, water and fire, each anxious to destroy the formations of its

opponent; and the historic documents which bear witness to that ancient

strife lie before us in the petrified or carbonified remains of extinct

forms of organic existence--the medals of creation.

It is only since yesterday that science has attempted to unriddle the

hieroglyphics in which the past history of our planet reveals itself to

man, and it stands to reason that in so difficult a study truth must

often be obscured by error; but although the geologist is still a mere

scholar, endeavouring to decipher the first chapters of a voluminous

work, yet even now the study of the physical revolutions of our globe

distinctly points out a period when the molten earth wandered, a ball

of liquid fire, through the desert realms of space. In those times,

so distant from ours that even the wildest flight of imagination is

unable to carry us over the intervening abyss, the waters of the ocean

were as yet mixed with the air, and formed a thick and hazy atmosphere

through which no radiant sunbeam, no soft lunar light, ever penetrated

to the fiery billows of molten rock, which at that time covered the

whole surface of the earth. What pictures of desolation rise before our

fancy, at the idea of yon boundless ocean of fluid stone, which rolled

from pole to pole without meeting on its wide way anything but itself.

Ever and ever in the dark-red clouds shone the reflection of that vast

conflagration, witnessed only by the eye of the Almighty, for organic

life could not exist on a globe which exclusively obeyed the physical and

chemical laws of inorganic nature.

But while the fiery mass with its surrounding atmosphere was circling

through the icy regions of ethereal space (the temperature of which is

computed to be lower than 60° R. below freezing point), it gradually

cooled, and its hitherto fluid surface began to harden to a solid crust.

Who can tell how many countless ages may have dropped one after the other

into the abyss of the past, ere thus much was accomplished; for the dense

atmosphere constantly threw back again upon the fiery earth-ball the heat

radiating from its surface, and the caloric of the vast body could escape

but very slowly into vacant space?

Thus millions of years may have gone by before the aqueous vapours, now

no longer obstinately repelled by the cooling earth-rind, condensed

into rain, and, falling in showers, gave birth to an incipient ocean.

But it must not be supposed that the waters obtained at once a tranquil

and undisturbed possession of their new domain, for, as soon as they

descended upon the earth, those endless elementary wars began, which,

with various fortunes, have continued to the present day.

As soon as the cooling earth-rind began to harden, it naturally

contracted, like all solid bodies when no longer subject to the influence

of expanding heat, and thus in the thin crust enormous fissures and

rents were formed, through which the fluid masses below gushed forth,

and, spreading in wide sheets over the surface, once more converted into

vapours the waters they met with in their fiery path.

But after all these revolutions and vicissitudes which opposed the birth

of ocean, perpetually destroying its perpetually renewed formation,

we come at last to a period when, in consequence of the constantly

decreasing temperature of the earth-rind, and its increasing thickness,

the waters at last conquered a permanent abode on its surface, and the

oceanic empire was definitively founded.

The scene has now changed; the sea of fire has disappeared, and water

covers the face of the earth. The rind is still too thin, and the

eruptions from below are still too fluid to form higher elevations above

the general surface: all is flat and even, and land nowhere rises above

the mirror of a boundless ocean.

This new state of things still affords the same spectacle of dreary

uniformity and solitude in all its horrors. The temperature of the waters

is yet too high, and they contain too many extraneous substances, too

many noxious vapours arise from the clefts of the earth-rind, the dense

atmosphere is still too much impregnated with poisons, to allow the

hidden germs of life anywhere to awaken. A strange and awful primitive

ocean rises and falls, rolls and rages, but nowhere does it beat against

a coast; no animal, no plant, grows and thrives in its bosom; no bird

flies over its expanse.

But meanwhile the hidden agency of Providence is unremittingly active in

preparing a new order of things. The earth-rind increases in thickness,

the crevices become narrower, and the fluid or semi-fluid masses escaping

through the clefts ascend to a more considerable height.

Thus the first islands are formed, and the first separation between the

dry land and the waters takes place. At the same time no less remarkable

changes occur, as well in the constitution of the waters as in that of

the atmosphere. The farther the glowing internal heat of the planet

retires from the surface, the greater is the quantity of water which

precipitates itself upon it. The ocean, obliged to relinquish part of its

surface to the dry land, makes up for the loss of extent by an increase

of depth, and the clearer atmosphere allows the enlivening sunbeam to

gild here the crest of a wave, there a naked rock.

And now also life awakens in the seas, but how often has it changed its

forms, and how often has Neptune displaced his boundaries since that

primordial dawn. Alternately rising or subsiding, what was once the

bottom of the ocean now forms the mountain crest, and whole islands and

continents have been gradually worn away and whelmed beneath the waves of

the sea, to arise and to be whelmed again. In every part of the world we

are able to trace these repeated changes in the fossil remains embedded

in the strata that have successively been deposited in the sea, and

then again raised above its level by volcanic agencies, and thus, by a

wonderful transposition, the history of the primitive ocean is revealed

to us by the tablets of the dry land. The indefatigable zeal of the

geologists has discovered no less than thirty-nine distinct fossiliferous

strata of different ages, and as many of these are again subdivided into

successive layers, frequently of a thickness of several thousand feet,

and each of them characterised by its peculiar organic remains, we may

form some idea of the vast spaces of time required for their formation.

[Illustration: Trilobite.]

The annals of the human race speak of the rise and downfall of nations

and dynasties, and stamp a couple of thousand years with the mark of high

antiquity; but each stratum or each leaf in the records of our globe has

witnessed the birth and the extinction of numerous families, genera, and

species of plants and animals, and shows us organic Nature as changeable

in time as she appears to us in space. As, when we sail to the southern

hemisphere, the stars of the northern firmament gradually sink below the

horizon, until finally entirely new constellations blaze upon us from the

nightly heavens; thus in the organic vestiges of the palæozoic seas we

find no form of life resembling those of the actual times, but every class