JELLY FISHES.
It has been remarked that we get our best ideas of geography from the
newspaper-man’s special correspondence in war time. Certainly, at such
times certain places that are not even marked on ordinary maps are
thrust into such prominence that they become familiar to thousands
who otherwise would never have known of their existence. In a similar
fashion many scraps and fragments of useful knowledge that will stick
in the memory will be picked up by the newspaper reader who is simply
bent on following the moves in the great political game. For instance,
it is not many years since a well-known Scots peer, in order to cast
ridicule upon his opponents, enlightened the world upon the subject
of Jelly-fish organization. The party he held up to scorn resembled
Jelly-fishes in his estimation because they were invertebrate--they
possessed no backbone, and could make no progress against the tide,
but were forced to float aimlessly with the current. The political
small-fry took up the parable from the venerable duke, some reproducing
it with variations that appeared marvellous indeed to the mere
naturalist; but it was soon quite generally known without recourse to
text-books, that the Jelly-fish was not a vertebrate animal, and that
it had no muscular power sufficient to enable it to move against the
tide.
Now these facts in the natural history of the _Medusæ_, elementary
though they be, are such as in the ordinary way might have taken
generations to get fixed on the public mind. Many persons who spend
their autumnal holiday at the seaside, become fairly familiar with
the more or less broken and lifeless forms of one or two common
species, as they get drifted upon the beach and are unable to get off
again; but they have probably little idea of the beauty and elegance
of these frail creatures when fully expanded and pulsating with life a
short distance from the shore.
There are two things which stand in the way of a more familiar
knowledge of these Jelly-fish, on the part of the public. First,
they are almost entirely composed of water, and, having no muscular
tissue, are soft and flabby to the touch--a characteristic which
inspires feelings of abhorrence in the average man or woman. A man may
courageously face a dangerous wild beast, and yet shrink with loathing
and disgust from contact with a slug or a Jelly-fish--though, with
strange inconsistency, he may swallow a living oyster with gusto!
Having found a stranded Jelly-fish on the beach, he will probably turn
it over with his stick, call to mind the Duke of Argyll’s political
simile, and pass on.
The second reason is that certain common forms have an unpleasant trick
of stinging slightly. This is a power given to them for the purpose of
paralysing small creatures they secure as food, but they have sometimes
mistakenly exerted it upon a timorous thin-skinned bather, against whom
they have drifted.
There are, however, only two or three of our native species that
have that power, and though they have been known from ancient days
as Sea-nettles, Stingers, and Stangers, there is no doubt that their
virulence has been greatly exaggerated. This exaggeration probably owes
something to the graphic word-picture of the late Professor Forbes,
in which he described the Hairy Stinger (_Cyanea capillata_). In
picturesque language he depicted it as “a most formidable creature, and
the terror of tender-skinned bathers. With its broad, tawny, festooned
and scalloped disk, often a full foot or more across, it flaps its
way through the yielding waters, and drags after it a long train of
riband-like arms, and seemingly interminable tails, marking its course,
when the body is far away from us. Once tangled in its trailing ‘hair,’
the unfortunate, who has recklessly ventured across the monster’s
path, soon writhes in prickly torture. Every struggle but binds the
poisonous threads more firmly round his body, and then there is no
escape, for when the winder of the fatal net finds his course impeded
by the terrified human wrestling in his coils, seeking no combat with
the mightier biped, he casts loose his envenomed arms and swims away.
The amputated weapons, severed from their parent body, vent vengeance
on the cause of their destruction, and sting as fiercely as if their
original proprietor gave the word of attack.”
No doubt Forbes had good grounds for his statement in the experience of
one of these delicate and nervous persons who suffer more mentally than
physically, and whose imaginative powers would create a horror out of
their contact with a spider, or even its web. The mischief is that the
bookmakers, who have no practical knowledge of their subjects, go on
quoting Forbes approvingly, and on this slight foundation characterise
the whole jelly-fish race as stinging creatures. It seems very probable
that some of the larger tropical forms that have the stinging power
are far more virulent than those inhabiting British seas; but I have
handled the Hairy Stinger and lifted it from the water with my bare
hands and experienced no discomfort from the operation.
The Rev. J. G. Wood improved upon Forbes, and described the pain
inflicted by _Cyanea_ as being at first like that following contact
with the stinging nettle of our hedgerows; getting more severe it
causes a sharp pain to flit right through the nervous system, the heart
and lungs suffer spasmodically. This state of affairs lasts for ten or
twelve hours, and then for several days the skin is so sensitive that
the sufferer can scarcely bear the contact of clothes; and it is months
before the shooting pains depart.
With such a character it is little wonder that the unscientific public
should decline an intimate acquaintance with the family. And yet the
story they have to tell is as marvellous as any that will be found in
the whole range of Mr. Lang’s Blue, Red, and Green Fairy Books. It is
the story of the insignificant and despised dwarf, who one day bursts
through his squalid exterior and stands revealed as the handsome prince
magnificently attired, whom all the princesses desire to marry. It
begins in the orthodox way with, Once upon a time there was a simple
and very tiny creature, with soft white flesh and no bones, who dwelt
on a rock on the sea-shore. He was just a little tube of jelly, and
though he had a mouth he had no head. His many arms were arranged
in a circle round his mouth, and from his body sprouted out several
creatures like himself, but much smaller. Learned men had examined
him and declared that his proper name was _Hydra tuba_. He remained
fixed to this rock from the autumn right through the winter’s storms,
and in the spring it was noticed that he was getting old, for a large
number of wrinkles appeared on his tubular body. Weeks went by and the
wrinkles became deeper and the edges of them turned up, so that the
upper part of the creature’s body looked like a dozen saucers piled up
one in the other. Then these saucers each grew a series of eight arms
from its edge, and the uppermost of the pile broke away from the others
and began to float off through the water. The next, and the next, and
every one of the remaining saucers floated off in the same fashion,
and those who watched them do so, say that they gradually grew into
glorious Marigolds or Sea-Jellies, with umbrella-like bodies of clear
jelly, marked on the top with rings and streaks of red, and all around
its edge each had a delicate fringe looking like the finest of silk.
And so they floated off to see the world and seek their fortunes.
[Illustration: LARVÆ OF AURELIA.]
The Jelly-fish produces ova, which develop _cilia_--eye-lash-like
processes, by means of which they swim through the water. Settling on
a rock or shell, they develop into _Hydra tuba_, with long tentacles,
as at _a_ _a_. Then comes the saucer-like stage, as at _b_; finally the
free-swimming segment, _c_, which ultimately becomes the huge creature
of our next illustration, which is so plentiful in our seas during
summer and early autumn.
Every person that has any acquaintance with Jelly-fishes at all knows
this species well--by sight. It is probable that many of those who
think they know it would be somewhat puzzled if asked to point out
the creature’s mouth and to give a rough outline of its organization.
It may be described roughly as umbrella-shaped. There is an arched
disk, from the centre of which, on the concave or lower surface there
depends a thick cylindrical body, the _manubrium_ or handle, sometimes
erroneously termed the _polypite_, which finally terminates in four
lobes assuming the form of trailing ribbons. In the centre of these
lobes is the creature’s mouth, and the stomach is continued from the
mouth _up_ the middle of the manubrium. Here digestion takes place,
and the nutriment thus obtained is carried up to the centre of the
umbrella, and thence distributed to all parts by means of nutrient
tubes which may be seen running straight from the centre to the
circumference.
Looked at from above, the _Aurelia_ will be seen to have its disk
symmetrically marked off into eight portions by these nutrient tubes,
each of which reaches the edge where there is a little notch, and then
continues round the margin. Now at the notch there is a ganglion, or
nerve centre, a kind of local brain, for the Jelly-fish is very low in
the scale of nervous organization, and possesses no central brain;
in fact, its ganglia are only the beginnings of a nervous system of
primitive type. At one time these spots were thought to be eyes,
and the Jelly-fishes were divided into naked-eyed and hooded-eyed
according to whether these sense organs were covered with a kind of
flap or not. It is now more clearly established that they are olfactory
organs, possibly in some cases they combine the functions of both
nose and eyes. They are known to naturalists as _tentaculocysts_. The
_Aurelia_ moves slowly through the water by the alternate expansion
and contraction of its umbrella-disk. The four crimson lunar marks
on the disk are the ovaries in which the eggs of the Jelly-fish are
produced. The eggs make their way through the stomach to the mouth of
the manubrium, where there are little cavities for their reception, and
here they stay until they have developed a fringe of cilia, when they
swim off. In this condition they are quite flat, and of old they were
regarded as a distinct species of animal under the name of _Planula_.
It afterwards becomes pear-shaped, tires of wandering, and settles
down on a rock or shell to undergo the series of developments we have
already described, every stage of which was formerly considered a
different animal and bore its special name.
[Illustration: MARIGOLD (_Aurelia aurita_).]
In spite of the structureless appearance presented by these
Jellies--owing to the presence of a thick layer of transparent
gelatinous material--they are endowed with true muscular fibres, which
are confined to the under surface of the umbrella, to the manubrium
and tentacles, and to a flap of the umbrella margin which is directed
inwards and known as the _velum_. It is by the contraction of the velum
that water is expelled from beneath, and this has the effect of forcing
the Jelly-fish in the opposite direction.
Somewhat similar to the _Aurelia_ in general form is the Hairy Stinger
(_Cyanæa capillata_), to which allusion has already been made. Its
umbrella is not so disk-like, but has a raised central dome, and its
edges are beautifully fringed with long threads. The lobes around
the mouth are developed into very long appendages, all frills and
furbelows. An allied species, _Cyanæa chrysaora_, has a very thick and
bulging manubrium, but no long streamers depending from it.
A very common form which swarms in harbours is _Thaumantias_, of which
there are several species. In these the jelly is very thick at the
crown of the umbrella, which is more bell-shaped than in _Aurelia_
or _Cyanæa_. The nutrient tubes are four, and the ovaries are beside
them. A very small species, _Turris digitalis_, is bell-shaped, with
a conical top and a deep fringe of tentacles round the margin. It
originates as a polypite on a so-called coralline similar to those
described in Chapter IV.
On our South-western shores we sometimes receive visits from
Jelly-fishes which must be regarded as distinguished foreigners. Among
these is the beautiful creature to which seamen give the name of
the “Portuguese Man o’ War” (_Physalia pelagica_). It is of a shape
entirely different from those we have noted. Instead of an umbrella
it has a spindle-shaped bladder distended with air and coloured with
blue, whilst along its upper surface there runs a beautiful pink frill
which serves as a sail. From the lower surface there hangs down a
cluster of long trailing corkscrews, beautifully coloured and capable
of stinging. Occasionally individuals from this floating colony develop
into Jelly-fish of distinct form, and swim away from the community.
[Illustration: THE “PORTUGUESE MAN O’ WAR” (_Physalia pelagica_).]
There seems no doubt of the stinging powers of this species, for Dr.
Bennett, a naturalist, has given us his account of the unpleasant
effects following upon his handling of this “Man o’ War.” He took hold
of the bladder, and the creature raised its long appendages, twining
them round his hands and stinging with great severity, and clinging so
tightly that he had difficulty in removing them. He says the pain was
like that caused by severe rheumatism, and extended up his arm to the
muscles of his chest. Symptoms of fever followed, with rapid pulse and
difficult breathing. This continued for three-quarters of an hour; but
even then he was not free, for his skin was marked with raised white
wheals for several hours. The tentacles, he says, can be thrown out
to a distance even of eighteen feet for the purpose of stinging its
prey. This species is often met by mariners in extensive fleets, so to
speak, and sometimes great numbers of them are wrecked upon the coasts
of Devon and Cornwall; occasionally they have been found on the eastern
shores of England, but they really belong to the Mediterranean and the
open ocean.
[Illustration: TUBE-MOUTHED SARSIA.]
A common form on the south coasts is the Tube-mouthed Sarsia (_Sarsia
tubulosa_), of which we give a portrait. It is bell-shaped, with what
looks like a very long clapper hanging from its centre, and four long
tentacles from the edge. The clapper is, of course, the manubrium,
and contains the mouth and stomach, which it can stretch out to very
accommodating proportions. The bell is only about half an inch in
height, but the manubrium is more than twice that length.
[Illustration: FORBES’ ÆQUOREA.]
Scarcely to be found on our coasts away from Devon and Cornwall are two
species of _Æquorea_, of which the one represented is dedicated to the
memory of the late Professor Edward Forbes, who did so much to extend
the knowledge of marine life, especially in relation to jelly-fishes,
anemones, star-fishes, and mollusks. It is therefore designated
_Æquorea forbesiana_, and a man might well feel proud to have so
beautiful a creature named with his name. It is a little larger than
our figure. Its upper portion is of thick crystalline jelly, coloured
with a lovely sky-blue tint lower down. Below the blue region are a
number of curved lines of bright crimson--the nutrient channels--and
the four lobes of the manubrium are similarly coloured. There are
streaming tentacles around the margin which lay hold of minute
creatures that pass by. The early history of this form of Jelly-fish is
unknown--whether it passes through stages resembling those of _Aurelia_
or of _Turris_, or attains the medusa-form direct from the egg. Any of
our readers that may have the opportunity for observing this beautiful
creature, should make a point of recording what he sees. It may be of
great assistance in working out the true relation of this species to
other forms.
One that must be classed with the “Portuguese Man o’ War” as a visitor
to our south-western coasts, is called the Sallee-Man (_Velella
scaphoidea_), a kind of Jelly-raft, upon which is hoisted a little
sail, and whose margin is fringed with tentacles. As in _Physalia_,
the underside of this float consists of a colony of many individuals,
which from time to time develop into free-swimming jellies.
But in spite of the colour-glories and imposing size of these larger
forms, we have upon our shores swarms of a veritable gem that, in
its way, for delicate beauty outshines them all. It is the Globe
Beröe (_Pleurobrachia pileus_), sometimes called the Sea Gooseberry.
In early summer, when the seas are still, and everything for five
fathoms or more can be clearly seen through the crystal waters of
the Cornish coast, this fairy form may be clearly seen in spite of
its short diameter (half-inch) and its perfect transparency. You are
lazily drifting in a boat, but your eye catches minute flashes of
iridescent colour in the water, and you must lean over the boat’s side
to see what it is. You then discover a number of these crystal globes
passing gracefully and without seeming effort through the water, not
always in our plane, now upwards to the surface, then downwards out of
reach. You are fascinated by the exquisite beauty, and hope the one
you are watching will not pass out of sight. As if in response to your
unexpressed wish, it ceases its downward course, and whilst suspending
itself in the water begins to revolve laterally. Your astonishment
increases, for you now see that it is furnished with paddle-wheels,
or else it is an animated paddle-wheel itself. No; a turn convinces
you again it is globular in form, but the paddles are equally obvious.
How can it be? What machinery turns them? and what are the two almost
interminable threads of gossamer that trail behind, below, or above it?
You watch your opportunity, and the next time one comes near the
surface you skilfully trap it in a glass jar, and then some of its
mystery is made clearer. The paddle-wheels are eight bands that
stretch from pole to pole, and across these at short intervals are
rows of “eye-lashes.” There is no rotatory motion of the bands, but
by the alternate depression and raising of the eye-lashes, an optical
illusion is produced. And yet the effect is the same as if these bands
revolved with fixed “floats;” the movements of the eye-lashes _row_ the
fragile vessel through the water, and with every movement the light
is reflected in prismatic tints that seem to pass in rapid flashes
along each of the eight bands. But whilst we have been investigating
the mystery of propulsion, what has become of those long attenuated
streamers? Broken off by our rough handling as we potted it? No; the
creature, as though sensible of danger, has carefully tucked them away
into suitable pockets. We can behold them through the clear jelly in
curved club-shaped receptacles. Look; here they come! The Beröe is
getting confident, and the tentacles stream out again to six times the
length of the animated globe. They can be lengthened or shortened at
the creature’s will; and each one is provided with an enormous number
of short side-branches, like tendrils on a vine. There is no pendulous
stomach and mouth hanging from the floating body, for the Beröe differs
from the Marigolds and Stingers, and is more closely allied with the
Sea-Anemones. Its mouth is at the top of the globe, and its digestive
cavity is central.
[Illustration: BERÖE AND YOUNG.]
I have described its appearance as seen from a boat, but it must not be
inferred that it cannot be obtained from the shore. A sharp eye will
see them in ports and harbours when gazing from low rocks or landing
slips. If our reader is desirous of watching these, a few should be
entrapped into a clear glass jar of sea-water, but other creatures
should not be introduced. I find that small crabs, prawns, or even
anemones are not to be trusted with _Pleurobrachia_, or these will
rapidly disappear.
The creatures we have brought together in this chapter under the
popular term Jelly-fish, really belong to very distinct groups of
animal life, and their developmental histories are different. Many of
them, in fact, are nothing more than buds from the branching Zoophytes
incorrectly called corallines that grow from shells and stones, and of
which we have had something to say in a previous chapter.
Agassiz has described a huge form of Stinger (_Cyanæa arctica_), with
an umbrella-disk like those we have mentioned, but measuring no less
than seven feet across, yet originating as a bud from a lowly coralline
not exceeding half an inch in stature. Others are not solitary
individuals, but companies of polyps that share the organ which bears
them through the waters. Such is the case with the _Physalia_ and
the _Velella_, the appendages of which consist not of one mouth and
stomach, but of many.
I remarked near the beginning of this chapter that the Jelly-fish was
very largely composed of water. Professor Owen, not content with having
to make an indefinite statement of that kind, went carefully into the
matter of pounds and ounces and grains. He said: “Let this fluid part
of a Medusa (Jelly-fish), which may weigh two pounds when recently
removed from the sea, drain from the solid parts of the body, and
these, when dried, will be represented by a thin film of membrane, not
exceeding thirty grains in weight.”
As a practical illustration of the value of having _that_ amount of
knowledge respecting such trivial things as Jelly-fish, the late Robert
Patterson, F.R.S., gives the following story, which was told to him as
a personal experience by an eminent zoologist, whose name he does not
mention.
“This gentleman had been delivering some zoological lectures in a
seaport town in Scotland, in the course of which he had adverted to
some of the most remarkable points in the economy of the Acalephæ.
After the lecture a farmer, who had been present, came forward and
inquired if he had understood him correctly, as having stated that
the Medusæ contained so little of solid material, that they might be
regarded as little else than a mass of animated sea-water. On being
answered in the affirmative, he remarked that it would have saved him
many a pound had he known that sooner, for he had been in the habit
of employing his men and horses carting away large quantities of
Jelly-fish from the shore, and using them as manure on his farm; and
he now believed they could have been of little more real use than
an equal load of sea-water. Assuming that so much as one ton weight
of Medusæ, recently thrown on the beach, had been carted away in one
load, it will be found that, according to the experiments of Professor
Owen, the entire quantity of solid material would be only about four
pounds of avoirdupois weight, an amount of solid material which, if
compressed, the farmer might, with ease, have carried home in one of
his coat pockets.”
Let me, in closing this very inadequate glimpse of a most interesting
group, add that many of these creatures contribute to that
phosphorescent appearance of the sea, which is such a wonder and a
revelation to those who behold it for the first time. The limits set
for the entire volume will not permit me to deal with all the British
species; but I trust sufficient has been said to awaken real interest
in these despised Stingers, Jellies, and Sea-blubbers.