CHAPTER II. The Molluscs

THE MOLLUSCS

PLATE VII

THE CUTTLE (1 and 2)

We now come to the Molluscs, or Soft-bodied Animals, of which there are a very great many. Some of them live in shells, like the oyster and the whelk, and are often spoken of as “shell-fishes.” But they are not really fishes at all, for they have no bones as fishes have, and are made in quite a different way. And there are just a few of them which have no shells at all.

One of these is that very curious creature which we call the Cuttle. You may sometimes find it in the rock-pools, lurking in the crevices among the rocks, or hiding under the masses of sea-weeds which grow round the edges. It has a soft, white, bag-like body, and a big head, on which are two great staring black eyes. Just above these eyes eight long slender arms spring out; for cuttles keep their arms on their heads instead of on their bodies! And another arm which is even longer still, and is flattened out at the end into a kind of oval plate, hangs down on either side.

All these arms are set with rows of round suckers, which are so strong that if even a small cuttle catches hold of you, it will not be very easy to make him let go. So if you do happen to find a cuttle in a rock-pool it will be better to watch him in the water, without attempting to catch him.

Down in the middle of all these branching arms, just where they spring from the head, are two very curious organs. The first of these is the beak, which is very strong, very sharp, and a good deal hooked. In fact, it is rather like that of a parrot. The other consists of two tubes which run downwards into the head, lying side by side together like the barrels of a double-barrelled gun.

These tubes are called the “siphon,” and they are used for three purposes.

First of all, they are used for breathing. The cuttle breathes water by means of gills, like those of fishes, which lie inside the head; and the water passes down to them through one of the siphon tubes, and then goes out again through the other.

Next, they are used for swimming. When a cuttle wants to swim it gathers all its arms together in front of its head, fills both its siphon tubes with water, and then squirts their contents out again as hard as it can. The result is that two jets of water come rushing out of its head with such force that the surrounding water cannot give way fast enough before them. So they push the cuttle backwards so swiftly that if it were to dart across the pool you would hardly be able to follow its movements.

The third use of the siphon tubes is a very strange one indeed. Sometimes while you are looking at a cuttle in a rock-pool, the water all round it will suddenly become quite dark, just as if a quantity of ink had been poured into the pool. And so it has; for inside its body the cuttle has a bag which contains a quantity of a deep black liquid called “sepia.” This bag is surrounded by powerful muscles, and opens into the siphon tubes; so that when the animal contracts the muscles, the sepia is squirted out into the pool. It always does this if it is frightened; and under cover of the darkened water it nearly always succeeds in making its escape.

Inside its body the cuttle also has a very curious object which is generally called a “cuttle-bone.” It is not really a bone, however, but is made of almost pure chalk, and seems to act as a kind of support for the bodily organs.

1. THE CUTTLE.

2. THE EGGS OF CUTTLE.]

Another very odd thing about the cuttle is the way in which it lays its eggs. These look just like purple grapes, and each has a small stalk, by means of which they are fastened together in bunches. Indeed, the fishermen always call them “sea-grapes.” You may often find them lying about upon the beach in early spring, and if you open one of them carefully, you will find a little baby cuttle inside it.

PLATE VIII

THE WHELK (1 and 2)

Everybody knows the shells of whelks by sight, and you can hardly take a walk along the sea-shore without seeing hundreds of them lying about on the beach. And great numbers of whelks are caught for human food, and also to serve as bait for fishes.

One very curious thing about whelks is the way in which they lay their eggs. Very often indeed, as you walk along the sandy sea-shore, you will notice round clusters of yellowish white eggs, which often go rolling along before the wind. Each of these clusters is about as big as a cricket-ball, and the eggs of which it is made up are about as large as peas. Now these are the eggs of whelks, and I think that every one who sees them must wonder how these creatures can possibly manage to lay such very big balls of eggs. For each egg-ball is at least two or three times as big as the biggest whelk.

But, after all, the explanation is quite a simple one. When the eggs are first laid they are very small indeed. Each is no bigger than a tiny pin’s head. Instead of having shells, however, these eggs have tough but very elastic skins; and these skins are made in such a way that while they allow water to soak in from the outside, they will not allow it to pass out again. So as soon as the eggs are dropped into the sea they begin to swell; and the result is that before very long each egg is as big as a good-sized pea.

If you pick up a cluster of these curious eggs in the early spring and open them, you will find inside each the shell of a very tiny whelk, which is almost ready to hatch out.

PLATE IX

THE DOG WHELK (1)

If you look in the ridges of small pebbles and bits of broken coal which you will meet with here and there on the sandy parts of the sea-shore, you are quite sure to find a number of very small whelk shells. They are brownish yellow outside, and pinkish white inside, and instead of being quite smooth, like those of the common whelk, they are covered with a number of ribs which run down from the peak to the margin. And these ribs are broken up in such a way that they look almost like rows of beads.

1. THE WHELK.

2. THE EGGS OF WHELK.]

These are the shells of the Dog Whelk, and if you wait until the tide is quite low, and then hunt about on the weed-covered rocks close to the edge of the sea, you will very likely find some of the living animals crawling about. They feed upon the sea-weeds by means of a curious organ called the tooth-ribbon. This is just a narrow strip of gristle, set with row upon row of very tiny hooked teeth; and by drawing this backwards and forwards over the leaves of the weeds the animal scrapes off very tiny pieces, which it then swallows.

In the tooth-ribbon of one of these whelks there are about a hundred rows of teeth, with about nine teeth in each row: so that the animal has nearly a thousand teeth altogether. But of course you can only see them by means of a powerful microscope.

PLATE IX

THE STING WINKLE (2)

Although this creature is called a “winkle” it is really one of the whelks. It is very common, and you may often find its empty shell lying upon the shore. It is white, or yellowish white, in colour, and is generally about an inch and a half in length, with several high ridges running down it from the top to the bottom, and a number of smaller ridges running crosswise between them.

You would not think that this could be a very dangerous creature, would you? It looks as harmless as it can possibly be, and certainly you need not be in the least afraid to pick up a sting winkle if you find one crawling about, for it cannot injure human beings. But to other shell-bearing molluscs it is a very terrible foe indeed. I dare say that you have often noticed, when you have been picking up shells on the sea-shore, that a good many of those shells had small round holes bored through them. Well, those holes were pierced by a sting winkle. For this animal is a creature of prey, and feeds entirely on other animals which live in shells; and when it meets with one it fastens itself to its victim’s shell, and drills a hole right through it by means of its tooth-ribbon. It then pokes the tooth-ribbon through the hole into the body of the animal inside, and draws it back again. As it does so, of course, the sharp hooked teeth drag away little bits of the animal’s flesh, which the sting winkle swallows. It then pokes its tooth-ribbon down again into the body of the victim, and so on, over and over again, until its hunger is satisfied.

PLATE IX

THE PERIWINKLE (3 and 4)

Of course you know the Periwinkle very well indeed by sight--and very likely by taste, too! So there is no need for me to describe it. But perhaps you did not know that there are two different kinds of periwinkles. One of these is the Common Periwinkle, which is very plentiful indeed on many parts of the coast. You may find it in thousands and thousands if you hunt about on the weed-covered rocks near the water’s edge when the tide is out, and no matter how many of them are caught, there always seem to be just as many again next day. This is the periwinkle which is used for food.

The other is the Dog Periwinkle. It is rather larger, and has a stouter shell. If you want to find it, you must look on the rocks about half-way between high and low water-marks, and there you will generally find it crawling about in numbers. But it is not good for food, because it often has a quantity of eggs inside its body, and inside these eggs the shells of the baby periwinkles are already formed, which make it dreadfully gritty. Thrushes, however, as well as a good many of the shore birds, do not mind this in the least, and they devour so many of both these kinds of periwinkles that it is quite a wonder that any are left alive.

PLATE IX

THE PURPURA (5)

In size and shape this very common creature is rather like the dog periwinkle. But its shell is white in colour instead of bluish black, and generally has two or three bands of light yellowish brown running round it. You may often find it crawling about on the weed-covered rocks when the tide is out.

1. THE DOG WHELK.

2. THE STING WINKLE.

3. THE PERIWINKLE.

4. THE DOG PERIWINKLE.

5. THE PURPURA.]

The purpura is quite a famous creature, because of the use which was made of it by the ancient Romans. I dare say you know that in days of old the colour of purple was very highly valued; and among the Romans only members of the royal family were allowed to dress in purple garments. Now this purple dye was obtained from the purpura. Inside its body this creature has a little bag which contains about a drop of a thick white liquid, rather like milk. Certainly it does not look in the least like purple dye. But if you were to squeeze it out on to a sheet of white paper, and to place it in the sunshine, you would very soon see that it was changing colour. In a few minutes’ time it would have turned to yellow. After a little time longer you would notice a blue tinge creeping into the yellow, and turning it to green; and by degrees the blue would become stronger and stronger, till the green disappeared. At last a crimson tinge would creep into the blue and turn it to purple; and this would be exactly the same as the famous purple dye which the ancient Romans valued so highly.

The eggs which are laid by the purpura are very curious indeed, for they are fastened down to stones by little stalks; so that each one looks rather like an egg-cup with an egg inside it. And inside each of these eggs are several little purpuras instead of only one.

PLATE X

THE SEA SNAIL (1)

This is one of the very commonest of all the shell-bearing molluscs. You may find it crawling about in numbers all over the weed-covered rocks which are left bare as the tide goes down. Its shell varies very much in colour, for it is sometimes bright yellow, and sometimes pale yellow, and sometimes olive green, and sometimes brown, and sometimes almost black. Indeed, you might almost think that there were half-a-dozen different kinds of these sea snails instead of only one.

These creatures have tooth-ribbons set with hundreds of tiny hooked teeth, just like those of the dog whelks, and they use them in feeding upon the leaves of sea-weeds in just the same way.

PLATE X

THE WENTLETRAP (2)

The Wentletrap is one of the most beautiful of all the shells which are to be found upon the shore. Indeed, I really think that it is quite the most beautiful. For the high ridges which stand out so boldly run round and round it in the most graceful curves, and the whole shell looks just as if it had been carved out of ivory.

1. THE SEA SNAIL.

2. THE WENTLETRAP.]

The wentletrap is sometimes known as the “staircase shell,” because the ridges which run round it are very much like those spiral staircases by which one climbs to the tops of church towers and other lofty buildings. If you want to find it, the best place to look is in the ridges of small pebbles which are washed up here and there on sandy coasts by the waves, and which are generally mixed up with broken coal which has been thrown out from passing ships. But it is not very common, and you must not be disappointed if you do not succeed in finding it.

PLATE XI

THE COMMON LIMPET (1)

This is a very common creature indeed, and you can find it in hundreds and thousands on any rocky part of the coast. Numbers of its empty shells are to be found lying about on the beach, and if you go down among the rocks when the tide is out you will often notice that in some places they are so covered with limpets that you can scarcely put the tip of your finger in between them.

These animals cling to the rocks in the most wonderful way. Indeed, if you take hold of a big limpet between your fingers you will not be able to move it in the least, even if you pull at it and push at it as hard as you can. But if you take the animal by surprise, and give it a sharp, sudden blow sideways with a stone, or the end of a stout stick, you can generally knock it off quite easily. And you will very often find that a deep ring-shaped mark has been worn away in the rock by the sharp edges of its shell.

However, limpets do not always remain clinging to the rocks, for they can crawl about quite as easily as snails can, by means of that soft, fleshy part of the body which we call the “foot.” And if you take them home alive, and put them into an aquarium, you may often see them creeping up and down the glass sides, through which you can examine their bodies quite easily.

PLATE XI

THE KEY-HOLE LIMPET (2)

There are a good many different kinds of limpets, of which one of the most curious is the Key-hole Limpet. It is generally found in rather deep water, but you may sometimes find it clinging to the rocks just above low-water mark. You must choose a season of “spring-tide,” however, for then the tide goes farther out than usual, and leaves behind it a good many creatures which at other times one hardly ever sees.

The shell of this creature is rather stouter than that of the common limpet, and has a number of ridges running down it from the peak to the margin. Even by these you can tell it at once. But if you look at it closely, you will also find that just at the top of the peak there is a hole shaped rather like a key-hole. Through this hole the animal squirts out the water which has passed over its gills; so that all the time that it is breathing, if only one could see it, a kind of little fountain is playing under water, spouting out from the top of its shell!

PLATE XI

THE SMOOTH LIMPET (3)

At first sight, perhaps, you would hardly take this creature for a limpet at all, for it is ever so much smaller than either the common or the key-hole limpets, and has a very thin and delicate shell indeed. It varies a good deal in colour, but generally the shell is pale brown, looking almost like polished horn, with eight or nine narrow streaks of bright blue running down from the peak to the margin. It is often called the “bonnet shell,” because in shape it is rather like an old-fashioned bonnet.

You may often find the empty shells of this creature lying upon the shore. But if you take them home you will find that as soon as they become dry the beautiful blue streaks begin to fade, and that after a few days you can hardly see them at all.

PLATE XI

THE CUP AND SAUCER LIMPET (4)

This is a very curious creature indeed. But if you want to see why its rather odd name was given to it, you must look inside its shell instead of outside. Then you will see that in the upper part is a curved plate which really looks very much like a tiny tea-cup, while the shell itself surrounds it just like a saucer. And if you were to examine the animal which lives inside it very carefully, and to pull out its long tooth-ribbon, you would find at the tip of it a curious little organ which looks just like a tea-spoon. So that we have cup, saucer, and spoon all in one!

Perhaps you may wonder what the odd little cup is for. Well, the fact is that the muscles by means of which the animal clings to the rock are very strong indeed. So, of course, there must be something else very strong to which they can be fastened, and this cup-shaped plate gives them a very firm hold.

The cup and saucer limpet is not a very common creature, and in many parts of the coast it is never met with at all. But if you stay by the sea-side on the south coast of England, you may sometimes find its empty shell lying upon the shore.

1. THE LIMPET.

2. THE KEY-HOLE LIMPET.

3. THE SMOOTH LIMPET.

4. THE CUP AND SAUCER LIMPET.]

PLATE XII

THE PAINTED TOP (1)

Tops are generally very common indeed on the sandy parts of the shore. You cannot possibly mistake their shells for those of any other creatures, for they are cone-shaped, looking very much like rather flattened sugar-loaves, and are generally very beautifully coloured. So pretty are they, indeed, that they are sometimes strung together and worn as necklaces, or used for ornamenting ladies’ dresses.

The painted top is one of the most beautiful of all these shells, for it is covered all over with spots and streaks and blotches of scarlet, and crimson, and pink, and purple, and white, and blue, and yellow! But all this lovely colouring is only on the outer coat of the shell, which is very easily chipped off. The consequence is that these shells are very often damaged by being tossed to and fro by the waves, and though you may often find twenty or thirty in the course of a morning, not more than two or three, perhaps, will be quite uninjured.

Tops are very useful creatures to have alive in an aquarium, for they keep the glass sides clean from the tiny green weeds which so quickly grow upon them. They do this by means of their tooth-ribbons, and you may see them crawling about on the glass walls and mowing down the weeds, just as a gardener cuts the grass on the lawn with his scythe.

PLATE XII

THE GREY TOP (2)

The painted top is rather a large shell, for it is often nearly an inch in height from the peak to the margin. But the Grey Top, which is even commoner still, is a good deal smaller. It is not nearly so brightly tinted as the painted top, for it is yellowish grey in colour, with zigzag black streaks running round and round it, which give it rather a mottled look. Still, it is a very pretty shell indeed.

If you look at a top shell from underneath, you will always find that there is a small hole in the bottom. This is the entrance to a passage which runs right up into the peak of the shell. In the grey top this hole is just about big enough to admit a rather fine needle.

PLATE XII

THE COWRY (3)

No doubt you have often found this very pretty shell, for on the sandy parts of our coasts it is sometimes very common. You may often find twenty or thirty cowries, indeed, in one of those ridges of pebbles and small coal which are washed up by every tide. But if you were to see the living animals crawling about I do not think that you would ever guess what they were, for their soft bodies come outside their shells, which they cover up so completely that you can hardly see them at all.

If you look on the upper part of the shell, you will see that a pale streak runs across it from one side to the other. This streak marks the line where the edges of the two sides of the body almost meet.

In some parts of the world cowry shells are used instead of money. It seems rather an easy way of getting rich, doesn’t it, just to go and pick up shells on the sea-shore? But then fifteen hundred of these cowries are only worth about a shilling, so that you would have to pick up a very great many even if you only wanted to do a day’s shopping! And then they are ever so much bigger than our English cowries, so that it would not be very easy to carry them about. You would have to take several sacks full of cowries with you when you went to make a purchase, instead of just keeping your money in a purse!

PLATE XII

THE CHITON (4)

The chiton is one of the oddest of all the shell-bearing molluscs; for it does not look like a mollusc at all. It looks much more like a kind of sea woodlouse, or a very tiny armadillo. For instead of having a single shell like a whelk or a periwinkle, or a double one like a cockle or an oyster, it has eight shelly plates on its back which overlap one another, just like the tiles on the roof of a house. And if you touch it, it will often roll itself up into a kind of ball, just like the pill-millepedes, or “monkey-peas,” which are so common in our gardens.

1. THE PAINTED TOP.

2. THE GREY TOP.

3. THE COWRY.

4. THE CHITON.]

This creature is called the Chiton, and if you want to find it you must go and look on the piles at the end of a pier, or on the rocks which are left bare at very low tides. There you will often find it in hundreds. Generally it is ashy grey in colour, but it varies a good deal in hue, and you will sometimes find examples which are streaked and mottled with pink, and orange, and white, and lilac, and chocolate brown.

Before a chiton reaches its perfect form it passes through a kind of caterpillar stage, and then turns into a sort of chrysalis, just as an insect does. And both the caterpillar and the chrysalis, strange to say, have eyes upon their heads, while the perfect chiton has none. But some chitons have eyes all over their shells instead, and in some of these very odd creatures between eleven and twelve thousand eyes have been counted, the shells being almost entirely covered with them; so that the animals may really be said to see with their whole bodies!