CHAPTER V.
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.
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.
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.
(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.
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.
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.
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.