STARFISHES
STARFISHES’ LEGS
Of course you know starfishes very well indeed by sight, for they are
flung up in numbers on the beach by almost every tide. But I wonder if
you know where their legs are!
Perhaps you did not know that they have any legs. But they have
hundreds and hundreds of them. Only, instead of keeping their legs
outside their bodies, as we keep ours, starfishes always keep them
inside, and poke them out through little holes in the skin when they
are required for use.
If you want to see the legs of a starfish, you can very easily do so.
First of all, you must catch a starfish, and make quite sure that he is
alive. You can easily find out that by picking him up. If his rays are
quite limp and flabby, and hang downwards from the disc, or middle part
of his body, so that they look rather like the legs of a table, he is
dead, and you can throw him away. But if they stand out stiffly he is
alive. Then just put him into a pool of sea-water, and wait. After a
few minutes you are almost sure to see that he is moving. Very slowly
he begins to glide along the bottom of the pool. If he comes to a
stone, he glides over it. If he comes to a rock, he glides up it. Then,
if you suddenly snatch him out of the water, and turn him upside down,
you will see his legs--little white fleshy objects waving about all
over the lower surface of his body. And if you look at them through a
good strong magnifying-glass, you will see that each one has a kind of
little cup at the end of a slender stem.
Now this cup is really a sucker, very much like the suckers of a
cuttle, only of course a great deal smaller. And the starfish walks by
pushing one or two of its rays forward, taking hold of the ground with
the suckers underneath them, and then pulling up the hinder rays and
taking hold with the suckers underneath those, and so on over and over
again.
PLATE XXXV
THE FIVE-FINGER STARFISH (1)
This is by far the commonest of all the starfishes. You can seldom
walk for even a short distance along the shore without seeing it. And
no doubt you might think that it must be a very harmless creature
indeed, for it does not look as if it could injure any other animal
in any way at all. Yet it is really a creature of prey, and feeds
upon shell-bearing molluscs, such as small bivalves, which it always
swallows whole. Then, when it has digested their bodies, it returns
their empty shells through its mouth. And it can even eat such big
creatures as mussels and oysters. Indeed, starfishes are the very worst
enemies of the oyster-beds, and in one fishery alone, on the coast of
North America, they are said to destroy more than ten thousand pounds’
worth of oysters every year!
[Illustration: PLATE XXXV
1. THE FIVE-FINGERED STARFISH.
2. THE BIRD’S-FOOT STARFISH.]
A very strange fact about the starfish is that if one of its rays is
cut off, a new one very soon grows in its place. Stranger still, if one
of these creatures is cut in two, each half begins to throw out new
rays, and in a few weeks’ time there are two starfishes instead of only
one! That seems impossible; doesn’t it? But yet it is perfectly true.
And another very curious fact about starfishes is that they keep their
eyes in very odd places--at the very tips of the rays. And in some
starfishes these eyes are furnished with lids, which can be opened and
shut!
PLATE XXXV
THE BIRD’S-FOOT STARFISH (2)
This is a very curious starfish, and a very handsome one as well. It
is curious, because its five rays are all joined together by membrane,
very much like the toes on a duck’s foot. That is why it is called the
“bird’s-foot” starfish. And it is handsome, because it has a scarlet
centre, a scarlet line all round the margin, and another one down the
inner margin of each ray, all the rest of the body being bright orange.
The bird’s-foot starfish is not very often seen, for it lives some
little way below low-water mark. But sometimes, when there has been a
violent storm at a season of spring-tide--and you will remember that
spring-tides come whenever there is a new moon or a full moon--it is
flung upon the beach by the retreating waves, and you may find it lying
on the sand when the tide is out.
PLATE XXXVI
THE SUN STARFISH
Sometimes you may find a very much larger and handsomer starfish lying
upon the shore. It has twelve rays instead of five, and is often as
much as eight or ten inches across. In fact, it looks very much like a
big sunflower. Generally it is bright scarlet in colour, but just now
and then one finds a sun starfish with a violet tinge; and sometimes,
while the middle part of the body is vermilion red, the rays are pale
rose-colour, or even pink.
[Illustration: PLATE XXXVI
THE SUN STARFISH.]
Like most of the starfishes, this animal has a very curious way of
protecting its eggs for some little time after they are laid. It heaps
them all up together into a pile, and then bends its rays downwards in
such a way that it stands upon their tips, looking just like a little
table with twelve very stout legs! It turns itself into a sort of cage,
in fact, with the eggs inside it, and so guards them carefully until
they hatch.
PLATE XXXVII
THE BRITTLE STARFISH
The Brittle Starfish is certainly the very oddest of all odd creatures,
for it not only grows new rays if the old ones should be torn off, but
actually breaks itself into pieces if it is startled or alarmed! And it
is such a timid animal that a slight touch, or even a shadow suddenly
falling upon it, will alarm it! Then it gives a kind of shudder, and
shatters itself into little bits, nothing being left but the central
disc and a heap of fragments! However, it does not appear to suffer
any pain, or to lose any blood, and the five wounds on the disc very
quickly heal. Then after a few days five little buds begin to show
themselves, which quickly grow into new rays, and in a few weeks’ time
the brittle starfish is as perfect as ever!
So ready are these creatures to break themselves up, that it is most
difficult to obtain a perfect brittle starfish for a museum.
Brittle starfishes are very active animals, and when they are alive
their long slender rays are always wriggling and coiling and twisting
about, hardly ever seeming to be still for a single moment. Indeed, one
naturalist compares a brittle starfish to five very long and active
centipedes stitched to a tiny pin-cushion!
There are several different kinds of these very curious animals, most
of which live at some little distance below low-water mark, and are
hardly ever caught except by means of the dredge. But sometimes you may
find one of them lying on the sand at the bottom of a pool among the
rocks.
[Illustration: PLATE XXXVII
THE BRITTLE STARFISH.]
PLATE XXXVIII
THE SEA URCHIN (1 and 2)
The “urchin,” as of course you know, is a common country name for the
hedgehog; and the Sea Urchin is so called because it is covered all
over with long spikes, just as a hedgehog is. These spines, however,
are very easily broken off, and when the animal dies, and its empty
shell is tossed to and fro by the waves, they are knocked off in a very
short time; so that when you meet with a sea urchin’s shell lying upon
the shore you nearly always find that it is covered with nothing more
than hundreds of very tiny pimples.
Now it is upon these little pimples that the spines grow. If you were
to examine one of the spines with a magnifying-glass you would find
that its base was hollow. This hollow base is just large enough to fit
over one of the pimples, to which it is fastened by a strong but rather
elastic muscle. So a sea urchin is able to move its spines about quite
freely. Indeed, it sometimes walks with them as well as with the little
sucker-feet, which it pokes out through tiny holes in the shell just as
a starfish does, moving a few forward at a time, and so hitching its
way along over the sand at the bottom of the sea.
If you succeed in finding a live sea urchin--and you can generally do
so without very much trouble, by hunting in the pools among the rocks
when the tide is out--you will notice that it has a very big mouth,
with five perfectly enormous teeth. They are so huge, indeed, that if
you had teeth as big, in proportion to your size, they would be about
as large as good big carving-knives!
On some parts of the coast sea urchins are eaten as food, being scooped
out of their shells with a spoon, just as we eat a boiled egg at
breakfast. For this reason they are sometimes known as “sea eggs,” and
those who have tried them say that they are very good indeed.
You would hardly think, perhaps, that a sea urchin and a starfish could
be related to one another, for they do not look in the least alike.
But if you take an urchin which has lost its spines, and examine it
carefully, you will see that it is really a kind of rolled-up starfish,
and you will be able to count its five rays quite easily.
[Illustration: PLATE XXXVIII
1. THE SEA URCHIN WITHOUT SPINES.
2. THE SEA URCHIN WITH SPINES.]
There is just one more thing that I must tell you about these very
curious creatures, and that is that they are very fond of covering
themselves all over with small stones, and little bits of broken shell,
and tiny pieces of sea-weed, in order that they may not be noticed.
They do this in a very odd way. I told you that they have numbers
of little sucker-feet, which they poke out through tiny holes in their
shells when they are required for use, just as the starfishes do.
Well, when they want to disguise themselves, they just push out two or
three hundred of these slender sucker-feet between their spines, and
take firm hold with them of any small objects that may be lying within
reach. In this manner they soon succeed in covering themselves all
over, and you might easily look at one of them as it lay at the bottom
of a rock-pool without recognising it at all.