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.
[Illustration: PLATE XXXI
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.
[Illustration: PLATE XXXII
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.
[Illustration: PLATE XXXIII
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.
[Illustration: PLATE XXXIV
1. THE NEMERTES.
2. THE NEREIS.]