CHAPTER VIII. Sea Cucumbers and Jellyfishes

SEA CUCUMBERS AND JELLYFISHES

PLATE XXXIX

THE SEA CUCUMBER (1)

If you grope about in the dark nooks and corners of a rock-pool, quite close down to the water’s edge, when the tide is out, you may perhaps find a curious little creature which looks rather like a greyish-white cucumber, with an odd feathery tuft at one end of its body. This is a Sea Cucumber, or Sea Gherkin, and is chiefly remarkable because it seems to suffer very much at times from eating something which does not agree with it. Then it cures itself in a very odd way indeed. It gets rid of almost all the inside of its body, reducing itself to very little more than an empty bag of skin, with just a little tuft at one end! It throws off its teeth, it throws off the lining of its throat, it throws off all its digestive organs. You would think that it would kill itself by doing this, wouldn’t you? But it does not. And before very long new teeth, a new throat lining, and new digestive organs grow in the place of the old ones, so that in a few weeks’ time the animal is just as perfect as it was before!

1. SEA CUCUMBER.

2. THE COMMON JELLYFISH.]

It seems rather hard to believe that an animal can treat itself in such a manner as this, and yet continue to live, doesn’t it? But remember that “truth is stranger than fiction,” and that some of the strangest animals of all are found among those which live in the sea.

PLATE XXXIX

JELLYFISHES (2)

Jellyfishes are among the very oddest creatures which are found in the sea; for their bodies are made up almost entirely of sea-water! It is quite true, of course, that if you cut them in two the water does not run away. But then if you cut a cucumber in two the water does not run away; and yet cucumbers are made almost entirely of water. And the reason why it does not run away is just the same in each case. Both in the cucumber and in the jellyfish the water is contained in a very large number of very tiny cells; and if you cut either of them across you only divide a very small number of the cells, so that only a very small quantity of water escapes. But if you leave a jellyfish lying on the beach in the hot sunshine, and come back to look for it two or three hours later, you will not find it. All that you will find will be a ring-shaped mark in the sand, showing where the jellyfish had been lying, with just a few threads of animal matter in the middle. All the rest will have evaporated, because it was nothing else but water.

All the same, jellyfishes are very wonderfully made; and perhaps the most wonderful thing of all about them is the fringe of long, slender threads which hangs down from the edges of their bodies. For these are the fishing-lines by means of which they catch their prey. Jellyfishes feed on all sorts of tiny creatures--the fry of fishes, and the zoeas of shrimps and prawns, for instance--and if you were to see one of these swim up against those terrible threads, you would notice that it at once became paralysed, and that in a very few moments it would be dead. The fact is that all the way along these threads are set with hundreds and hundreds of tiny oval cells, each of which has a very slender dart, with a barbed tip, coiled up like a watch-spring inside it. And the cells are made in such a way that as soon as they are touched they fly open, and the little darts leap out. So, you see, if any small creature swims up against the threads numbers of darts at once bury themselves in its body. And, as these darts are poisoned, it dies in a very short time.

Jellyfishes can swim through the water by spreading and contracting their umbrella-shaped bodies, and you may sometimes see them travelling about in such enormous numbers that the water is perfectly thick with them.

PLATE XL

THE STINGING JELLYFISH (1)

Sometimes, after a strong south-westerly wind has been blowing for a day or two in the early part of the autumn, you may find a brownish yellow jellyfish lying upon the shore. It has a circular body about as big as a soup-plate, fringed all the way round with great masses of long yellow hairs. And if you find one of these creatures you are almost sure to find another before very long, and then another, and then another; for they nearly always swim about in shoals together.

Now, if you do meet with one of these jellyfishes, be very careful not to touch it with your bare hands. And if you should happen to be bathing, and to see one floating in the water near you, just get out of its way as fast as you possibly can. For those long yellow threads which hang down from the margin of its body sting just like nettles, and the least touch from them will cause a great deal of pain. If you have a thin skin, indeed, the sting of this terrible jellyfish may make you very seriously ill, and several weeks may pass before the effects of the poison pass away.

Yet the fishing-threads of this jellyfish are scarcely thicker than hairs, and the little darts which do so much mischief are so slender that you cannot see them at all without the help of a good strong microscope. Doesn’t it seem strange that such tiny weapons can be so dreadfully poisonous?

PLATE XL

THE SEA ACORN (2)

This is a very common jellyfish indeed; yet hardly anybody ever sees it. That is because it is very small and very transparent, so that as it swims about in the water it is almost invisible. And if it is flung up on the beach it dries up in a very few minutes. But if you want to look at it, you can very easily do so. On a warm, still day, when the sea is quite smooth, just dip a small net into the water, and work it gently to and fro. Then lift it out and examine the sides carefully, and you are almost sure to see three or four little lumps of jelly, not much bigger than peas. These are sea acorns, and if you put them into a glass vessel of perfectly clean sea-water, you will very soon find that they are swimming about. For though you cannot see the animals themselves, which are quite as transparent as the water, you will notice little flashes of coloured light, sometimes blue, sometimes green, sometimes yellow, and sometimes red, which just gleam out for about half a quarter of a second, and then disappear. You might almost think that a tiny rainbow had been dissolved in the water.

1. THE STINGING JELLYFISH.

2. THE SEA ACORN.]

The fact is this. Running round the oval body of the sea acorn are eight narrow bands, and on each of these are a number of very tiny scales, placed one above another, which keep on rising and falling again, like so many little trap-doors. These scales are really paddles, by means of which the animal drives itself through the water, and as they move up and down they catch the rays of light and break them up, just like that triangular piece of glass which we call a “prism.” And though you cannot see the jellyfish itself you can see these little flashes of coloured light, and so can trace the course of the little creature as it travels slowly along.

This curious jellyfish has only two fishing-threads, which hang down from the lower part of its body. But from each of these a number of little side-threads spring out, just like the “snoods” on the lines which fishermen use in the sea. And the animal is always throwing these out and drawing them in again, so that it really “fishes” for the tiny little creatures on which it feeds.