CHAPTER VI. The Sea Worms

THE SEA WORMS

PLATE XXXI

THE SEA MOUSE (1)

If you go down among the rocks when the tide is out, and hunt in the muddy pools near low-water mark, you will be almost sure to find a very odd-looking creature indeed. It is generally between three or four inches long, and although it is called a “Sea Mouse” it looks very much more like a hairy slug; for its whole body is covered with a matted coat of bristles. But it is really a kind of sea worm. And it looks just about as dull and dingy as any creature can possibly be.

Yet in reality it is one of the most beautiful animals which are found in the sea, and if you want to see its beauty, all that you have to do is to wash it. For the bristly coat which covers its body is a kind of filter, which strains out the mud from the water which passes to the gills; and it soon becomes so choked with mud that you cannot see what the animal is really like at all. All that it wants, however, is a really good bath: so just take it to a pool of clear sea-water, and rinse it thoroughly. Then take it to another pool, and rinse it again. Then take it to a third pool, and rinse it again; and go on rinsing it till every atom of mud has been washed out of its hairy coating. And then, if you look at it in the bright sunshine, I am quite sure that you will be astonished to find what a lovely creature it really is. For all the colours of the rainbow, and ever so many more besides, seem to be chasing one another over its bristles, and altering with every movement and every change of light. Doesn’t it seem strange that an animal so beautiful as this should live with all its beauty covered up, so that hardly any eye can ever see it?

But these bristles have another use besides that of a filter. Each of them is really a kind of long, slender spear with a barbed tip, which can be used as a weapon of defence. If you were to look at one of these bristly spears through a good strong microscope you would see that it was edged on both sides with sharp little hooked teeth, looking very much like those of a shark. But you need not be in the least afraid to handle a sea mouse, for although these slender spears look so formidable, they are not nearly strong enough to pierce your skin.

1. THE SEA MOUSE.

2. THE SABELLA.]

PLATE XXXI

THE SABELLA (2)

A good many different kinds of worms live on the sea-shore, and one of the most curious of these is the Sabella. For it lives in long, narrow tubes made of tiny grains of sand, which it sticks together with a kind of natural glue. You may find these tubes in great numbers just about low-water mark, and hundreds and hundreds of them are often twisted up together in great masses, which are sometimes several feet in diameter. The worms can travel up and down these tubes by means of tufts of stiff little bristles on each side of their bodies; and sometimes they will leave them altogether, crawl about on the sand for a little while, and then make new ones. And if you keep them alive in a glass vessel filled with sea-water, with a little sand at the bottom, you can watch them building their wonderful tubes, carefully choosing grains of sand of just the proper size, arranging them in position just as a bricklayer lays bricks, and then sticking them firmly together.

PLATE XXXII

THE SERPULA (1 and 2)

If you look down into the pools among the rocks when the tide is out you may often see a number of long, twisted tubes fastened to the surface of the stones at the bottom. These are the dwellings of a very curious sea-shore worm called the Serpula, and if you lift one of the stones out of the water, and look down into the tubes, you will nearly always see a bright scarlet object lying just beneath the entrance. And then you may be quite sure that the animal is alive.

Now suppose that you carry the stone home with you, just as it is, and put it into a vessel of sea-water. After an hour or two you will find that the little scarlet objects have been poked out of the tubes, and that they are really tiny stoppers, just like little corks, which exactly fit the entrance when they are pulled inside. And you will also find that a plume of feathery objects, which are also bright scarlet in colour, is projecting out of the mouth of each tube. These red plumes are the gills of the worms, and they will often remain spread for hours at a time. But if you startle the animals--if your shadow falls upon them, for instance--they will draw themselves down into their tubes in about half a quarter of a second, and every tube will be corked up by its tiny stopper, just as before.

1. THE SERPULA.

2. SERPULAS IN TUBES.]

On the sides of its body the serpula has tufts of little bristly hairs, just as the sabella has, which allow it to move up and down its tube. But in order to enable it to draw itself back as quickly as possible in moments of danger, it has a row of little hooked teeth on its back, by means of which it can take a firm hold of the lining of its burrow. I think you will be rather surprised when I tell you how many of these teeth there are in the row. Just fancy! Each serpula has between thirteen and fourteen thousand!

If you look at the oysters in a fishmonger’s shop, you may often see the tubes of these curious worms fastened to the surface of the shells.

PLATE XXXIII

THE TEREBELLA (1)

This is another of the worms which live in tubes. You can generally find its wonderful little dwellings by hunting in the small puddles of sea-water which are left on the sands when the tide goes out. And you can always tell them from those of the sabella and the serpula by the curious little fringe round the entrance, which is made of the tiniest grains of sand fastened together into slender threads. The tube itself is made of larger grains, and is so tough and leathery that you can give it quite a hard pull without breaking it. But as it is at least a foot long, and is nearly always carried down underneath rocks or big stones, you will not find it at all easy to dig it up. And the moment that you alarm the little animal inside it always makes its way right down to the very bottom of its tube.

Sometimes a terebella will leave its tube and go for a little swim in the pool, wriggling its way through the water by first doubling its body up and then stretching it out, over and over again. But it very soon gets tired with its exertions, and sinks down to the bottom of the pool to rest. Then, after awhile, it will set busily to work, and make a new tube to live in instead of the old one.

There is another kind of terebella, called the Shell-binder, which makes its tube of little bits of broken shell instead of grains of sand. You may find the ends of these tubes sticking up out of the sand about half-way between high and low-water mark. But they run down so deeply that you will have to dig very hard indeed if you want to get them out of the ground.

1. THE TEREBELLA.

2. THE LUG WORM.]

PLATE XXXIII

THE LUG WORM (2)

On any muddy stretch of beach, when the tide is out, you may see numbers and numbers of little twisted casts, just like those which you may find on the lawn in the garden on any warm damp morning. These are made by Lug Worms, or “logs,” as the fishermen generally call them, and they really consist of sand which the worm has swallowed during the last three or four hours. For lug worms burrow by swallowing mouthful after mouthful of sand, until they can swallow no more. They eat their way down into the sand, in fact, just as earth-worms eat their way down into the ground. And when their bodies are quite filled with sand, they come up to the entrances of their burrows and pour it out in the little twisty coils which everybody who has walked on the shore knows so well by sight.

If you take a spade and dig down into the muddy sand you can find these worms in great numbers. They are just about as big as earth-worms, and are of all sorts of colours, some being brown, and some dark green, and some purple, and some crimson. But on each side of the body they always have thirteen pairs of bright scarlet tufts. These are the little gills by means of which they breathe, and if you put them under a microscope they look just like tiny bushes with brilliant red leaves.

You would think, perhaps, that when a lug worm bores its way through the loose sand, the sides of its burrow would fall in behind it as fast as it passed along. But from the surface of its body it pours out a thin, sticky liquid which binds the sand together, and forms a kind of lining to the burrow, like the brickwork of a railway tunnel. The burrow is generally about two feet deep, and the worm always lives in it with its head downwards. The worm itself, when fully grown, is from six to ten inches long.

PLATE XXXIV

THE NEMERTES (1)

This is quite one of the most curious creatures to be found on the sea-shore. It hides under large stones at the bottom of the pools, and looks rather like a tangled boot-lace. But it is really a kind of leech-like worm, and the wonderful thing about it is that it can stretch its body out to almost any length, just as if it were made of elastic. It always does this in catching its prey, which it seizes by means of its sucker-like mouth, which has a kind of beak inside it. Then it “plays” its victim just as an angler “plays” a fish, sometimes stretching its body out to a length of fifteen or twenty feet, then drawing it in again to a length of three or four, and so on over and over again, until its prisoner is quite exhausted, when it proceeds to devour it.

PLATE XXXIV

THE NEREIS (2)

The Nereis is a very common sea-side worm, and you can nearly always find it by turning over the stones on the shore as the tide goes out. It is brown in colour, with a dark red line along the back; and if you look at it in the sunlight you will see flashes of bright blue playing over the surface of its skin. And underneath it is of the most delicate pink, with a glossy look which reminds one of mother-of-pearl. It is one of the largest of all the worms, for it often grows to a length of nearly two feet.

If you examine the back of a nereis, you will find a row of little tufted organs running right along it. Each of these really consists of two little flaps, which are folded together as long as the worm remains still. But as soon as it begins to swim they open out and wave up and down in the water; for they are really tiny paddles, by means of which the nereis rows itself along. Altogether there are about four hundred pairs of these little flaps, which move in perfect time together, just like the oars of a well-rowed boat. Perhaps you may have seen a boat-race, and you noticed, no doubt, how all the eight oars rose and fell exactly at the same instant, as regularly as if they were moved by machinery. Well, imagine a very long boat indeed rowed by four hundred little rowers instead of only by eight, and each with two oars instead of one, and then you will have some idea of what a nereis looks like as it goes swimming through the water.

This curious worm does not live only under stones, for it is sometimes found hiding in the whelk shells which are occupied by hermit crabs, the worm and the crab living in the same shell together, and never seeming to interfere with one another.

1. THE NEMERTES.

2. THE NEREIS.]