In this wonderful nest the spider lays her eggs and brings up her family. When the little ones have been hatched, of course, the air in the nest very soon becomes too impure to breathe. Then the little spiders cling tightly to the walls, while the mother gets outside and tilts the whole nest sideways, so that all the exhausted air floats up in one big bubble to the surface. Then she pulls the nest back into position, hurries up to the top of thewater and brings down a bubble of air, and then another, and so on until the nest is filled with air all over again.
If you ever catch one of these spiders, and keep it for awhile in a jar of water with a little piece of water-weed, you may see it spinning its wonderful nest, and filling it with air, perhaps half a dozen times a day.
Gossamers
Before we leave the spiders altogether, we must tell you something about the wonderful little creatures called gossamers. These are really the young of a good many different kinds of spiders. It often happens, of course, that several families, with perhaps five or six hundred little ones in each, are all living quite close to one another. The result is that there is not sufficient food for them all. So they make up their minds to go out into the world and seek their fortunes; and this is how they do it.
Choosing a warm, sunny morning in the early part of the autumn, all the little spiders climb the nearest bush, and each one makes its way to the very tip of a leaf. Then, clinging firmly to its hold, it begins to pour out a very slender thread of silk from one of its spinnerets. You know that on warm, sunny days the air near the ground soon becomes heated and rises, as hot air always does; and in rising it carries up these delicate gossamer-threads, as they are called, with it. Still the little spiders hold on, and pour out their lines, till at last each has several feet of thread rising straight up into the air above it. Then suddenly they all let go, and are carried up into the air at the ends of their own threads. So they go on, up and up and up, till at last they meet a gentle breeze, which carries them along with it. So, perhaps, they travel for thirty, forty, or fifty miles, or even farther still. And when at last they make up their minds to descend, all that they have to do is to roll up the threads which have been supporting them, and down they come floating gently back to earth. One good name for them is ballooning spiders.
Haven't you sometimes found on a warm autumn morning that all the trees and bushes, and even the grass and low plants,are quite covered with threads of silk? The next time you see such a sight look carefully, and you will find that on every thread a little baby spider is sitting. Then you may be quite sure that all these little spiders set out early in the morning to seek their fortunes, and that, borne up by their slender threads, they have traveled for many long miles through the air.
Scorpions
These formidable creatures are closely related to the spiders. They are found in all warm countries, with the exception of New Zealand, and may easily be known by two facts. In the first place, in front of the legs they have a pair of great, strong claws, which look very much like those of a crab. And in the second place, the last five joints of the body are narrowed into a long, slender tail, at the end of which is a claw-like sting. When they attack an enemy, or seize a victim, they grasp it with the claws, turn the tail over the back, and force the sting into its body. And the poison which is introduced into the wound is so powerful that the sting of a large scorpion is almost as severe as the bite of an adder.
During the daytime scorpions hide away under stones and logs, or in crevices in the ground, or perhaps under the loose bark of dead trees. But very soon after sunset they come out from their retreats and prowl about all night long in search of insects; and it is at such times that they invade camps and houses, get into shoes, etc., and persons get stung unless they are very careful.
Centipedes and Millepedes
One can easily recognize centipedes by the great number of their feet. The name centipede, indeed, means hundred-footed. None of these creatures, however, have exactly a hundred limbs. Some only have fifteen pairs of legs; some have as many as one hundred and twenty-one pairs. But whether they be many or few, the number of pairs is always odd.
Another very curious fact about centipedes is that they haveno less than four pairs of jaws. But the fourth pair take the form of fangs, which are very stout and strong, and very much curved, while at their base, just inside the head, is a little bag of poison. In the northern centipedes, which are quite small, the fangs are not large enough, nor the poison sufficiently strong, to cause a serious wound. But some of the tropical species, which grow to the length of nearly a foot, are quite as venomous as the largest scorpions.
The food of these creatures consists chiefly of worms and insects. But the larger ones will kill lizards, and even mice, and have been known to prey upon victims actually larger than themselves.
The eggs of centipedes are laid in little clusters on the ground in some dark, damp nook, and when they have all been deposited the mother centipede coils herself round them, and there remains guarding them until they hatch.
Millepedes, in some ways, are very much like centipedes; but they only have two pairs of jaws instead of four, and they are nearly all vegetable-feeders. The long, smooth, and slenderJulusmillepedes are plentiful in every garden. And in tropical countries they sometimes grow to a length of six inches. Even the largest, however, are perfectly harmless, for they have no poison-fangs as the centipedes have, and the only way in which they ever attempt to defend themselves is by pouring out a small drop or two of a fluid which smells rather nasty, and no doubt protects them from the attacks of birds.
We now come to a very important class of animals, which includes the crabs, the lobsters, the shrimps, and the prawns. These creatures, together with the mollusks, are often called shell-fish, although the "shell" of a crab is not in the least like the shell of an oyster, for example, or like that of a whelk, or a snail. It is only a sort of crust upon the skin, made chiefly of carbonate of lime. That is why these animals are calledcrustaceans; and instead of growing, like true shells, this coat never increases in size at all.
But crabs and lobsters grow? Yes: but not as other animals do, a little every day. They only grow, as a rule, once a year; and they get a whole twelvemonth's growth into about two days!
When, in warm weather, the proper time approaches, they hide away in some crevice among the rocks, where none of their enemies are likely to find them. This is because they are going to throw off their so-called shells; and they know that when these are gone they will be deprived of their natural armor, and of their weapons too, and so will be quite at the mercy even of foes much smaller than themselves. Then a very strange thing happens. Part of their flesh actually turns to water! Sometimes, if you happen to take up a crab in a fish-market, and shake it, you will hear water swishing about inside it. This is a "watery" crab, and is not good to eat; for it was just about to change its "shell" when it was caught. A good deal of its flesh has actually turned to water.
Now this always happens a few days before the "shell" is thrown off; and the animal wriggles and twists about inside it, in order to loosen the attachments which bind it to its body. It also rubs its feelers against its legs, and its legs against one another, in order to loosen their hard coverings in the same way. This goes on, perhaps, for three or four days. Then,suddenly, the "shell" splits across, and the animal, with a tremendous effort, springs right out of it, while the "shell" closes up again, and looks just as it did before. One might really think that there were two crabs instead of only one.
For some little time the animal now lies perfectly still. It is exhausted by its efforts, and its muscles are so cramped that they feel quite hard to the touch. This cramp soon passes off, however; and then at once the animal begins to grow. It grows very fast. Indeed, you can almostseeit grow, for a whole year's increase in size has to take place in about forty-eight hours. Then a fresh crust is gradually formed upon the skin, and two or three days later the animal is once more clad in a coat of mail, and is ready to leave its retreat and face its enemies. For a whole twelvemonth after this it grows no bigger. But at the end of that time the process is repeated, and so on, year after year, until at last the animal reaches its full size.
Forms of Crustaceans
The bodies of the crustacean animals are made up of a number of rings, or segments, like those of the insects. But there are always twenty of these rings, instead of thirteen; six forming the head, while there are eight in the thorax and six in the hind body.
Then—again like the insects—crustaceans have feelers, or antennæ, upon their heads. You can see these very well indeed in a lobster or a shrimp. But instead of having one pair of these organs, as insects have, they always possess two pairs. And it is rather curious to find that at the base of the front pair there are two little organs which seem to be ears, specially formed for hearing in the water, while at the base of the second pair are two other little organs which seem to serve as a nose, specially made for smelling in the water.
And—once more like the insects—crustaceans have to pass through several different forms before they reach the perfect state. They are hatched in the first place from eggs, which the mother animal carries about with her for some little timefirmly fastened to the hairs of the swimmerets, which we find under the hind part of her body. You will often find a shrimp with quite a large bunch of these eggs; and if you look at them carefully with a good strong magnifying-glass, you will see that they are all glued down to hairs.
Inside each of these eggs an odd little creature is formed, which is called the nauplius. Sometimes it is hatched while still in that state, and swims about through the water. But in almost all the higher crustaceans a change takes place before it leaves the egg, and it appears at last in the form of a zoëa.
This is a kind of crustacean caterpillar, and a very odd little creature it is. A great naturalist once described it as an animal "with goggle eyes, a hawk's beak, a scorpion's tail, a rhinoceros' horn, and a body fringed with legs, yet hardly bigger than a grain of sand!" Certainly it does not look in the least like the crab, or lobster, or shrimp into which it is going, by and by, to turn. And it swims in the oddest way possible, by turning endless somersaults in the water!
These zoëas are sometimes found in immense shoals, the surface of the sea being quite thick with them for miles. And they are useful little creatures, for they feed on the tiny scraps of decaying matter which are always floating about in the sea, just as tadpoles and gnat-grubs do in ponds, thus helping to keep the water pure. But a very great number of them are devoured by whales. For when whalebone-whales are hungry, they swim with open mouths through a shoal of these little creatures, and then strain them out of the water by means of the whalebone fringe which hangs down from the upper jaw.
After a time the zoëa throws off its skin and appears in quite a different form. It is now called a megalopa, or big-eyed creature, because it has very large eyes, which are usually set on foot-stalks, and project to quite a long distance from the sides of the head. And as the zoëa is a kind of crustacean caterpillar, so the megalopa is a kind of crustacean chrysalis. It generally has a long, slender body, made up of several joints. And it swims by flapping this to and fro in the water.
Crabs
First among the crustaceans come the crabs, of which there are a great many different kinds. They are distinguished by having the tail tucked under the body, and firmly soldered, so to speak, to the "shell" on either side.
You can find several kinds of these creatures by hunting among the rocks on the sea-shore when the tide is out. There is the common shore-crab, for example, which is green in color. It is generally to be found hiding under masses of growing seaweed. But sometimes you may see it prowling about in search of prey. It is wonderfully active, and will even pounce upon the sandhoppers as they go skipping about, just as a hunting-spider will pounce upon flies, seldom or never missing its aim. It will catch flies, too, leaping upon them when they settle, and shutting them up, as it were, in a kind of cage formed by its legs. Then it pokes one claw carefully into this cage, seizes the prisoners, pulls them to pieces, and pokes the fragments into its mouth.
Swimming about in the pools, too, you may often find a fiddler-crab, which is so called because its movements in the water rather remind one of a man who is playing the violin. You will find that its hind legs are very much flattened, and are fringed with stiff hairs, so that they may be used as oars. In fact, the animal rows itself through the water. Both these crabs, sad to say, are cannibals, and are always ready to attack and devour their own kind.
Then there is the edible crab, or blue crab, which is common on many parts of our coasts. The edible crab of Europe is somewhat different. You are not likely to meet with the larger examples, which live in deeper water. But even the smaller ones can give a very sharp nip with their great claws, and you will find it as well to be very careful in handling them. The best plan is to seize them with the thumb and finger just behind these claws, then they are perfectly harmless. The larger crabs, which sometimes weigh as much as twelve pounds, are extremely powerful, and in more than one case a man hasbeen killed by them, having been seized by the wrist as he was groping among the rocks, and held in a grip from which he could not break away until he was drowned by the rising tide.
These crabs are captured by means of crab-pots, made of basketwork, which have the entrance so formed that while the crabs can easily enter, they cannot possibly get out again. These pots are baited with pieces of fresh fish, and are then weighted with stones, and lowered to the bottom of the sea among the rocks, at a depth of from three to about twenty fathoms. They are also caught on lines baited with meat. No hook is needed, for the crab clings to the meat till it reaches the surface of the water, when it must be flung into the boat or somehow captured quickly, before it has time to let go and sink.
Some crabs live on dry land, sometimes at a distance of two or three miles from the sea, which they only visit at intervals. Among these are the famous calling-crabs, found in many of the warmer parts of the world. These crabs obtain their name from the fact that one of the great claws of the male is very much larger than the other. So big is it, indeed, that it has to be held aloft over the body when the animal is running, in order to prevent it from losing its balance and toppling over. And as soon as the crab begins to move this huge claw is jerked up and down, just as if the creature were "calling," or beckoning, to its companions. The calling-crabs live in burrows in the sand, which are often placed as close to one another as those in a rabbit-warren.
Hermit-Crabs
Next we come to those small, curious creatures known as hermit-crabs, which form a kind of connecting link between the crabs and the lobsters, for their tails, instead of being firmly soldered down underneath their bodies, are quite free.
But the odd thing about these animals is that their tails have no shelly covering. The front part of the body is protected by a coat of mail, just as it is in all the other crabs; but the hind part is quite bare and soft. The consequence is that ahermit-crab is always very nervous indeed about his tail. He is dreadfully afraid that one of his many enemies may creep up behind, and bite it when he is not looking. So he always tucks it away in an empty shell like that of a whelk or a sea-snail, which he drags about with him wherever he goes!
You may often find these curious crabs by hunting for them in the pools among the rocks at low water. The crab always sits just inside the entrance of the shell, which he closes and guards with one of his great claws. And if you try to pull him out, you will find that you are quite unable to do so, for he has a pair of strong pincers at the end of his body, by which he holds the shell so firmly that you can tear him in two without forcing him to loose his grip.
Sometimes you will find that a sea-anemone has fastened itself to the edge of a shell in which a hermit-crab is living. This is a great advantage to the crab; for while there are many fishes which would be quite ready to crunch him up, shell and all, no fish will ever meddle with a sea-anemone. So as long as the anemone remains on his shell he is perfectly safe.
And this plan is also a great advantage to the anemone, which is sure to get plenty of food without any trouble. For when the crab finds the dead body of some small creature, and begins to pull it to pieces, a quantity of small fragments is sure to float upward in the water. And the anemone catches them with its spreading tentacles and feeds upon them.
The Robber-Crab
One of the most extraordinary crustaceans is this, which is found in many of the islands in the Indian Ocean. It is like the hermit-crabs in some ways, but the tail is covered with shelly plates, just like the rest of the body; and instead of living in shells in the sea, it lives in deep burrows on dry land.
But the oddest thing of all with regard to this crab is its food. What do you think it feeds upon? Cocoanuts! That seems impossible, doesn't it? One would imagine that the crab could never get the nuts open. But it manages in this way: First of all, it pulls away the fibers from that end of the nut at which thethree eyeholes are situated. With one of its stout claws it then hammers away at one of these till it breaks its way through. And finally, after allowing the milk to run away, it pokes its hind claws, which are very slender indeed, through the opening and picks out the white fleshy part of the nut a little piece at a time.
It is said, too, that this crab sometimes opens a nut by poking the smaller joint of one of its claws into the hole, and then striking it over and over again upon a big stone.
The burrow of the robber-crab is rather a deep one, and is nearly always situated beneath the roots of a tree. And at the end of the burrow is a large chamber, in which the crab piles up a quantity of cocoanut fiber to serve as a bed.
Lobsters
Of course you know the lobster very well by sight; and perhaps you know that until it is boiled it is black, not red. But do you know how it swims? If so, you know that it has two different ways of swimming. When it is not in a hurry it swims slowly forward by means of its swimmerets, of which it has five pairs under the hinder part of its body. But if it is startled or alarmed it swims swiftly backward by means of its tail.
If you look at a lobster's tail, you will see that it is very broad and flat, and that on either side of it are two plates, which are quite as flat, and, if anything, are rather broader. So, when these are spread, the tail looks like a fan. And the animal swims by first stretching out its body almost straight, and then doubling it suddenly with all its force. As it does so, the tail and the tail-plates spread out, and act very much like a broad oar. And the result is that the lobster darts swiftly backward through the water. Shrimps and prawns swim in exactly the same way.
Lobsters are very quarrelsome creatures, and are constantly fighting; and it very often happens that in these battles they pull off one another's limbs. They seem to feel very little pain, however, from such an injury, and before very long new legs begin to grow in place of the old ones, so that in course of time the wounded creatures are as perfect as ever.
Sometimes lobsters will throw off their limbs when they are not attacked at all. They do so, for example, if they are suddenly frightened; and it is said that if a heavy gun is fired near the surface of the water, every lobster for a long way round will shed its great claws in alarm.
You will notice, on looking at a lobster, that one of the great claws is a good deal smaller than the other; and sometimes people think that this is a new claw which is growing in place of one that has been lost, and that it has not yet reached its full size. This, however, is a mistake, for one of the claws is always much bigger than the other; and the reason is that they are used for different purposes. The larger claw is intended as a weapon, and with this the lobster fights. But the smaller one is chiefly employed as a kind of anchor, by means of which the animal can cling to the weeds or rocks at the bottom of the sea.
Lobsters are caught in pots made of basketwork, just as crabs are. But they are not nearly so dainty as crabs, and do not mind whether the bait is fresh or putrid. They are always very much attracted, too, by any object that glitters, and many a lobster has been lured to its death merely by one or two oyster-shells hung up inside the pot in such a manner as to show the shining pearly interior.
Crayfish
The crayfish is a kind of fresh-water lobster, which is found commonly in many parts of the world, and numerously in the central and southern parts of the United States. Most species hide all day long under the projecting edges of big stones, or in holes in the bank, only coming out after nightfall to search for food. The British crayfish is said to be particularly fond of the deserted burrow of a water-vole, and as it sits inside it always guards the entrance with its great claws, striking fiercely at any enemy which may be bold enough to come within reach.
One, at least, of the American kinds sinks its own burrows, in the form of round holes in the soil of damp meadows. These holes go down to water, which the animal cannot live long away from; and a part of the soil dug out is piled about the mouth ofthe hole in a little tower or chimney, sometimes several inches high.
In Europe crayfish are eaten and regarded as a delicacy when properly cooked; and there is no reason why the American ones should not be equally good, but they are rarely if ever used as food by us. The flesh tastes like that of the lobster, but is more tender.
Shrimps and Prawns
These are really only tiny lobsters, and if you examine them carefully you will find that their bodies are made in exactly the same way. They swim, too, by means of their tails, and dart about so swiftly that it is almost impossible to follow their movements. You may often find them in numbers in the pools which are left among the rocks by the retreating tide. But as they are almost colorless until they are boiled, it is very difficult to see them, and they look just like shadows darting to and fro in the water.
You can easily tell a prawn from a shrimp, for the beak which projects in front of its head is covered with sharp points, which are almost exactly like the teeth of a saw. It feeds upon the bodies of the various small creatures which die by millions every day. In this way it helps to keep the water of the sea pure. It feeds in a curious way, tearing off tiny scraps of flesh with the little pincers at the tips of the second pair of legs, and poking them into its mouth one after another. The sides of these limbs are covered with hairs, so that they form little brushes; and with these the prawn carefully cleans its body and limbs, rubbing off every little speck of dirt which may happen to cling to them.
Sandhoppers
You can hardly walk along a sand shore when the tide is rising without seeing sandhoppers leaping and twisting about in thousands. If you turn over a bunch of seaweed which has been flung up by the waves just above high-water mark, you are almostsure to find forty or fifty of these odd little creatures hiding under it. In some ways they are rather like shrimps. But they differ from them in having their eyes set on the head itself, instead of on little foot-stalks projecting from it. And they have no carapace, or shelly shield, covering the middle part of the body.
How do these creatures hop? By first doubling up their bodies, and then straightening them out again with a kind of jerk. It is exactly opposite, in fact, to the way in which shrimps and lobsters swim.
Sandhoppers do not follow the retreating tide, but bury themselves in the sand very soon after the waves have ceased to break over them. Even when the surface of the sand is quite dry you can find their burrows by stamping with your foot, when a number of little round holes will suddenly open all round you.
These creatures have wonderfully sharp little teeth, and if you allowed a swarm of them to rest for a little while on your handkerchief you would most likely find that it was full of tiny holes when you took it up. They will eat almost anything, either animal or vegetable, and are quite as useful as the shrimps and prawns in helping to keep the sea-water pure. But they have a great many enemies, for sea-birds, land-birds, crabs, and all sorts of other creatures, destroy them literally in millions.
The Fresh-water Shrimp
This shrimp is very much like the sandhopper in some ways. You may find it in numbers in almost any small stream or rivulet. It hides under stones, or in little crevices in the bank, darting out now and then to seize one of the tiny creatures upon which it feeds, and then hurrying back with it to its retreat. When it is in the water it travels along by a series of jerks; sometimes swimming with its back uppermost, and sometimes on one side. But if it is placed on dry ground it is perfectly helpless, for its legs are not nearly strong enough to carry it, and the only result of its struggles is to turn it round and round in a screw-like manner without forcing it forward at all.
Woodlice
These odd little creatures are really crustaceans, although they belong to quite a different group from that about which you have just been reading. They simply swarm in all damp places. Under logs, in heaps of decaying leaves, and under the bark of dead trees, they are always extremely plentiful, and you may also find them in hundreds in cellars and outhouses. There are several different kinds, one of which rolls itself up into a ball when it is touched or alarmed. This is called the pill-woodlouse, or pill-armadillo. Another one is remarkable for the fact that the mother carries her little ones about with her in a pouch underneath her body for some little time after they are born.
Barnacles
You would hardly think that barnacles were crustaceans, would you? Yet they are; though certainly they are very unlike any of those about which we have been telling. You can find them in countless thousands upon the rocks which are left bare by the tide at low water, and very often the hulls of ships are so covered with them that the vessels have to be taken into dry dock and thoroughly cleaned before they are fit to start upon a voyage.
These animals fasten themselves down to their hold by a kind of foot-stalk, which is firmly attached by a very strong cement. The upper part of the body becomes covered with a shell, consisting of several pieces, or valves; and between these, six odd little limbs can be poked out at will. These limbs are very hairy, and are always waving about, so as to sweep into the mouth any tiny scraps of food which may be floating in the water.
There are a great many kinds of barnacles, some of which look very much like acorns, and grow to a considerable size. These are known as acorn-barnacles. And there is another, shaped rather like a piece of round tube, which burrows into the skin of whales, in which it spends all the remainder of itslife! Sometimes it bores its way down so far that it actually reaches the blubber.
The young of these strange creatures pass through several transformations, just like those of the lobster and the crab. First, there is a nauplius, then a zoëa, and then a megalopa, all of which swim freely about in the water, never fastening themselves down until they are ready to pass into the perfect form.
LIFE ON THE SEA-BOTTOM.LIFE ON THE SEA-BOTTOM.1. Sticklebacks. 2. Carp. 3, 5, 6, 13, 17. Sea-Anemones. 4. Shrimps. 7. Prawn. 8. Fiddler Crab. 9. Starfish. 10. Sea-horses. 11. Edible Mussels. 12. Serpula Worm. 14. Hermit-Crab in Whelk's Shell. 15. Sea-urchins. 16. Rock Crab. 18. Polyzoan (Flustra). 19. Corallines (Gorgonia).
1. Sticklebacks. 2. Carp. 3, 5, 6, 13, 17. Sea-Anemones. 4. Shrimps. 7. Prawn. 8. Fiddler Crab. 9. Starfish. 10. Sea-horses. 11. Edible Mussels. 12. Serpula Worm. 14. Hermit-Crab in Whelk's Shell. 15. Sea-urchins. 16. Rock Crab. 18. Polyzoan (Flustra). 19. Corallines (Gorgonia).
Next in order to the crustaceans comes a group of animals which live in the sea, and which are known as echinoderms, which simply means spiny-skins. This group includes the sea-urchins, the starfishes, and the sea-cucumbers.
Sea-Urchins
You can find a good many of these creatures when you go to the seaside, by hunting about on the beach at low water. In some places on rocky coasts sea-urchins are very common. Sometimes they are known as sea-eggs, and in many countries they are actually boiled and eaten as food, just as we eat the eggs of fowls and ducks. And their shells are so thickly covered with spines that they look just like little hedgehogs which have rolled themselves up into balls.
When the animal is alive it can move these spines at will, each of them being fastened to the shell by a ball-and-socket joint, just like those which we described to you when we were telling about the vertebræ of the snakes. But after it has been dead for a few days they are nearly always knocked off by the action of the waves, so that the shell is left quite smooth and bare.
By means of these spines a sea-urchin can bury itself in the sand at the bottom of the sea in a very short time, only just a little funnel-shaped pit being left to show where it is hiding. And in some of the larger kinds they are really formidable weapons, for they grow to a length of eight or ten inches, and are so sharp and strong that they can actually pierce the sole of a stout shoe. Besides this, they have poison-glands connected with them, so that they can easily inflict a really serious wound.
In the shell of a sea-urchin are a number of little holes, through which the animal pokes out most curious sucker-likefeet when it wants to climb about over the rocks. By means of the suckers on the upper part of the shell it often clings to small stones, which it sometimes gathers up in such numbers as to conceal itself entirely from sight.
Just inside the mouth of the urchin are five very large chisel-like teeth. These are formed just like the front teeth of the rodent animals, and grow as fast as they are worn away.
Sea-urchins are not numerous on the Atlantic shores of North America, because these shores are not rocky except in the cold north. One small flat kind, however, occurs in the deep waters off this coast, and its cases are often cast up on the beaches and are called sand-dollars. On the Pacific coast, however, sea-urchins are common and well known; and the Indians of the northwest coast boil them and eat them greedily.
Starfishes
More plentiful on both coasts, and extremely numerous and harmful in all the bays and sounds from Florida to Maine, are the starfishes, or fivefingers, as the oystermen call them. But although they are so abundant, very few people seem to know what curious creatures they are.
The starfish has hundreds of little sucker-like feet, just like those of the sea-urchin. You cannot see these, as a rule, because the starfish keeps them tucked away inside its skin. But when it wants to use them it can poke them out in a moment.
If you want to look at these odd little feet, the best way to do so is to take a live starfish, put it at the bottom of a pool of sea-water, and then wait patiently for ten minutes or a quarter of an hour. By the end of that time you are almost sure to see that the animal is slowly moving. Then snatch it out of the water, turn it upside down, and you will see hundreds of little white objects waving about on the lower surface of its body. These are its feet, and if you look at them through a good strong magnifying-glass, you will see that they are shaped just like wine-glasses, each having a kind of fleshy cup at the end of a slender stem. And at the end of the cup is the sucker.
In the very middle of the lower part of the body of a starfish is its mouth. This is generally rather large, for the animal feeds chiefly on shell-bearing animals which it swallows whole, shells and all. Then, when it has digested the bodies of its victims, it turns their empty shells out again through its mouth. That is an odd way of feeding, isn't it? But sometimes it feeds in an odder way still, for when it finds a creature which is too big to be swallowed, it will actually turn its own digestive organs out of its mouth, wrap them round its victim, hold them there until it is digested, and then drag them in again and go off to look for another victim!
Starfishes eat a great many oysters in this way. So many do they destroy, indeed, that they are the very worst foes with which oyster-fishers have to deal, and the damage done by them in one single oyster-bed on the coast of North America is estimated at no less than fifty thousand dollars every year.
There are a great many different kinds of starfishes. One, for example, has twelve rays instead of five, and looks very much like a live sunflower. This is called the sun-star. Another has its five rays all joined together by webbing, very much like the toes on a duck's foot, and is known as the bird's-foot star. It is a very handsome creature, for while the greater part of its body is bright yellow, it has a broad band of crimson running all the way round the outer margin, and another stripe of the same color down the outer edges of each ray, while the membrane between them is fringed with yellow hairs. But you are not very likely to find it, for it lives in rather deep water, and is hardly ever caught except by means of that useful net which is called a dredge.
Odder by far than any of these, however, are the brittle-stars, which owe their name to their extraordinary habit of breaking themselves to pieces! They nearly always do this if they are touched or alarmed. In fact, they are so ready to do so that it is very difficult indeed to obtain a perfect brittle-star for a museum. The creature just gives a kind of shudder, and its five rays all drop off and break up into little pieces, all that is left of the animal being just the central disk. But it does not appear to suffer any pain, and loses hardly any blood. Andbefore very long new rays grow in the place of the old ones, so that in a few weeks' time the starfish is just as perfect as ever!
The brittle-stars have five very long and very slender rays, which are generally fringed on either side with yellow hairs. And these rays are hardly ever still, but twist and writhe and curl about so actively that they really look almost like so many centipedes! It is by no means so numerous as the fivefinger, and is so easily broken that it is hard to find a whole one on the beach.
Very curious, too, is the basket-star, which at first sight does not look like a starfish at all. The reason is that, close to its body, each of the five rays divides into two. Then each of the branches divides into two again, and each of those into two more, and so on over and over again, till sometimes there are more than eighty thousand little arms altogether!
The basket-star catches its prey by means of these wonderful rays, which it wraps all round it in the form of a circular basket. It is not at all a common creature, and is only found in deep water.
But perhaps the oddest of all these creatures is the rosy feather-star, which actually grows on a stalk while it is young, and looks just like a flower with its petals spread. The stalk, which is fastened down to a rock at the bottom of the sea, is made up of a great number of tiny joints, and grows longer and longer. And when it reaches its full length the animal breaks itself free and swims away, leaving the stem behind.
The rosy feather-star lives in rather deep water, from which it is sometimes brought up by means of the dredge. It can crawl about on the ground by means of its sucker-like feet, and can swim through the water with some little speed. And very often, to save itself trouble, it will cling by means of its rays to a piece of floating wood, and allow itself to be carried for long distances by the waves.
In Great Britain these may often be found near shore, but the American feather-stars all live in very deep water. They are all that remain of a large class of such animals which abounded in the very ancient seas, whose fossil remains are called stone-lilies.
Sea-Cucumbers
These are really relations of the starfishes, although they do not look in the least like them; for they closely resemble the vegetable after which they are named. In front of the slit at one end of the body, however, which serves as a mouth, there is a feathery tuft. This consists of delicate little tentacles, or feelers, by means of which the animal fishes for its food, and which can be drawn back inside the body when it is not hungry. And if it were not for this tuft one really might almost mistake the animal for a grayish-white cucumber.
We saw just now that the brittle-star breaks off its own rays at the slightest alarm. But the sea-cucumber, in this way, is even odder still, for if it eats anything which disagrees with it, as it sometimes does, it turns all its digestive organs out of its mouth, cuts them off, and allows them to float away! Then for three or four months it is very little else than a bag of empty skin, with just a slit at one end and a tuft in front of it. But at the end of that time new digestive organs begin to grow in the place of the old ones, and very soon the sea-cucumber is as perfect as ever!
Isn't that a remarkable way of curing indigestion?
Some of the sea-cucumbers grow to a very great size. One indeed, when fully grown, is nearly six feet long. And in China they are largely used as food, under the name of trepang, and are looked upon as a great dainty.
The class of the mollusks is a very large one, for at least fifty thousand different kinds of these creatures are already known, while new ones are constantly being discovered. They may be described as soft-bodied, boneless animals, which are enclosed in a tough muscular skin called the mantle. And they are divided into five orders, the first of which includes the singular creatures known as squids, or cuttles.
You may sometimes find these animals hiding in the pools which are left among the rocks when the tide goes out; and you can recognize them at once by the long, fleshy tentacles, or arms, which spring from the upper part of the head. Some of them have ten of these arms, and are called decapods; the rest have only eight and are known as octopods. And the lower surface of each arm is furnished with a row of circular suckers, the grip of which is so powerful that the tentacle may even be torn in two without causing it to release its hold. Indeed, if quite a small cuttle were to seize you with one of its arms, you would not find it at all easy to make it let go again without killing it.
The cuttles employ these suckers for two purposes. In the first place, they use them in walking. When a cuttle is crawling along at the bottom of the sea it pushes one or two tentacles forward, takes firm hold of a rock or a large stone with the suckers underneath them, pulls up the body, and then thrusts them forward again. And in the second place, they use them in catching their prey. Quite large victims are often seized by cuttles, and when once the deadly suckers have fastened upon them there is no hope of escape. In spite of their struggles one tentacle after another comes closing in, till they are completely surrounded by the long, slimy arms, soft almost as jelly, yet strong as steel. Then they are pushed down against the sharp, strong beak, by which they are quickly torn in pieces.
On the upper part of the head of the cuttle there is anothercurious organ known as the siphon, which consists of two tubes lying side by side together, like the barrels of a double-barreled gun. This organ is used in three different ways.
First, it is used in breathing. The cuttles, like the fishes, breathe water, by means of gills. These gills lie inside the head, and the water passes down to them through one of the siphon-tubes, and then out again through the other.
Next, it is used in swimming. When cuttles are not in a hurry they crawl along by means of their long tentacles, as we told you just now. But if they are startled, or alarmed in any way, they fold all their tentacles together in a straight line, fill both the siphon-tubes with water, and then squirt it out again as hard as they possibly can. The result is, of course, that they are driven rapidly backward by the recoil, just like the dragonfly grub, of which we have read.
But the third use of the siphon-tubes is the most curious. If you discover a small cuttle hiding in a rock-pool, you will very likely find that the water all round it suddenly grows dark as night, just as if a quantity of ink had been poured into it. The fact is this. Inside its body the cuttle has a bag filled with a quantity of a deep-black liquid called sepia. This bag is surrounded by strong bands of muscle, and opens into the siphon-tubes. So, you see, when the animal suddenly contracts the muscular bands, the sepia is squirted out through the siphon into the water, which is immediately darkened for some little distance all round. And under cover of the darkness the animal escapes.
The eggs of the cuttle are laid in a very curious way, for they are fastened by little stalks to a stem of seaweed, so that they look very much like a bunch of grapes. Fishermen, indeed, nearly always speak of them as "sea-grapes."
The cuttles which are found in the British seas are always quite small. But in some parts of the ocean these creatures grow to a giant size. Fragments of the tentacles of an enormous cuttle, for instance, have been found lying on the coast of Newfoundland; and by careful calculation it was shown that if the animal to which they belonged had stretched them out at right angles to its body, they would actually have measured more than eighty feet from tip to tip!
These huge creatures seem to form the principal food of the spermaceti-whale.
The Chambered Nautilus
This animal is a near relation of the cuttles. It lives in a shell, which cannot increase in size. The mollusk itself grows, however, and soon becomes too big to live in its home; so it forms a second and larger compartment outside the first one. Time after time this happens, till at last the shell consists of about thirty-six chambers, only the outside one being inhabited by the nautilus.
This shell is often more than a foot in diameter. But if you were to see it when it is first taken out of the sea you would never think that it was a shell at all. Indeed it looks much more like a big shapeless lump of blubber, for the animal covers it entirely with its muscular mantle, so that the shell itself is completely concealed.
Very little is known of the habits of the chambered nautilus, for it lives at the bottom of the sea, at a depth of two or three hundred fathoms. It is found in various parts of the Indian and Pacific oceans.
Gastropods
A great many well-known creatures belong to this large group, first upon the list being the slugs. We need not describe these animals, but perhaps you will be surprised to hear that they have shells! These shells are very small, however, and are entirely covered over by the mantle, so that they cannot be seen unless the body is dissected.
Slugs have the most wonderful power of stretching out and drawing up their bodies. You may see one of these creatures crawling about on a damp evening, and measuring fully five inches in length. But at the slightest touch it begins to contract, and in a few seconds it is just a shapeless lump, scarcely half as long as it was before. The odd little tentacles are drawn back into the head, and the head is drawn back into the body so thatif you did not happen to know what it was you might easily mistake it for a pebble.
On the right-hand side of a slug's body, as it crawls along, you will notice a rather large and almost round hole. This is the entrance to the breathing-organs, which lie just behind the head and underneath the mantle.
During the daytime slugs remain in hiding, lying behind the loose bark of dead trees, or under logs and large stones, or in heaps of decaying leaves. And if the weather is very hot and dry they do not come out even at night, for they very soon die if they are deprived of moisture. But on warm, damp evenings they travel for long distances in search of food, which is almost entirely of a vegetable character. In Europe every gardener knows what injury they do to gardens there, but in America the slugs are practically harmless.
A good many different kinds of slugs are found in Great Britain. The largest of all is the great gray slug, which often grows to a length of more than six inches. Then the black slug is very common in many parts of the country. It is not always black, however, for one may often find examples which are brown, or yellow, or gray, or even white. The milky slug, which has a thick creamy slime, is plentiful everywhere. And sometimes one may dig up a very curious slug—testacella—which feeds on earthworms, and follows them down to the very bottom of their burrows. When the weather is cold, this slug makes a kind of cocoon of earth and slime, and lies fast asleep inside it, often for many months at a time.
Snails
In many ways snails are very much like slugs, but they have a shell large enough to contain the entire body when the animal withdraws inside it. Several hundred different kinds of snails are found in North America, and many more in other parts of the world, varying in size from that of a small pinhead to that of a big walnut. Some are exceedingly numerous, others so rare and singular in their living-places that they are highly prized by conchologists. All snails lay eggs, usually in damp soil;and if you will turn over an old log in the woods in summer, you will be almost certain to find some of the minute shining globules. When winter draws near all the snails go into hiding, and they have a most curious way of closing the entrances to their shells by making little doors across them, composed partly of slime and partly of very small fragments of earth. This is in order to prevent the frosty air from getting in and killing them. But it would never do, of course, to keep all the air out, for in that case they would be unable to breathe. So they always leave a tiny hole in the middle of each door, through which just enough air can pass to prevent them from being suffocated.
Among the largest of all is the edible snail, which is largely used for food in many parts of Europe and is imported into the United States and pickled, to be eaten by those who like this delicacy.
Most of the gastropod mollusks, however, live in the water, some inhabiting ponds and streams, while others dwell in the sea.
In almost every brook and every ditch, for example, you may find water-snails of different kinds. Some are quite flat, and some are conical and pointed. Some are as large as land-snails, and some are so tiny that they are almost always overlooked. Most of them feed upon decaying leaves, and they have an odd way of traveling by floating upside down at the surface of the water, each with its broad fleshy "foot" expanded, so as to convert themselves into tiny boats. You may sometimes see quite a fleet of these little creatures being carried along by the stream. But if you throw a stone into the water they all sink down to the bottom at once, and do not resume their journey until many hours or even days afterward.
The eggs of this snail are laid in long jelly-like ribbons, which are generally fastened either to the stems and leaves of water-plants, or under the edges of large stones lying at the bottom of the stream. A very large number of gastropods live in the sea. One of the best known of these is the whelk, of which one reads in all books of English natural history. On almost every sandy and shingly beach, in Western Europe, one may find it lying about in hundreds; and even in large inland towns one often sees whelks for sale, both in fishmongers' shopsand on barrows at the corners of the streets. Its eggs are one of the curiosities of the sea-beach—small, yellowish-white objects about the size of peas, made of tough, parchment-like skin, and fastened together in bundles about as big as cricket-balls. You may often find these bundles on the shore in dozens; and most likely you will wonder how the whelk ever managed to lay a batch of eggs a good deal bigger than itself.
But the fact is that the eggs of the whelk are just like those of the frog. When they are first laid they are very tiny; but the tough skin of which they are made is very elastic, so that it will stretch almost like a piece of india-rubber. Besides this, it has the curious property of allowing water to soak in from the outside, but not to pass out again. So as soon as the eggs are dropped into the sea they begin to swell, and before very long they are quite twenty or thirty times as large as they were when they were first laid.
We do not have these whelks in North America, but we have a variety of small gastropods, whose shells are sometimes rough and coiled in a spiral form, sometimes round like land-snails, and of various sizes. One of them is the purpura, which has many ribs, and broad dark and light stripes running spirally. The purpura of the Mediterranean is famous for the purple dye obtained from its body; but our species yields such a dye also in small quantity. This was the dye anciently known as Tyrian purple. It is contained in a little bag behind the throat, which holds just one small drop of liquid, and no more. And if you were to see it you would never think that it was dye at all, for it looks only like rather yellowish water. But if it is squeezed out on a sheet of white paper, and laid in the sunshine, it very soon begins to change color. First it becomes green, then blue, and then purple. And it is really the dye which the ancient Romans valued so highly that no one who did not belong to the royal family was allowed to dress in purple raiment.
Borers
In many parts of our eastern coast occur in great numbers two or three kinds of small, rough, spiral gastropods, calledborers by the fishermen, who hate them because of the great number of oysters they kill. Each of these spends its whole life in seeking and devouring other shell-bearing mollusks. It kills and eats these in a very curious way. Like all the gastropods, it possesses what we call a tooth-ribbon—that is, a narrow strip of very tough gristle in its mouth; set with row upon row of sharp, notched, flinty teeth. There are some times more than six thousand of these teeth, and although they are so small that they cannot be seen without the aid of a powerful microscope, they are nevertheless very formidable. For every tooth is hooked, with the points of the hook directed toward the throat.
The tooth-ribbon is used in this way: When a borer meets with a victim, it fastens itself to it by means of its fleshy, muscular "foot." Then it bores a round hole through its shell, as neatly as if it had been pierced by a drill. And then it pokes the tooth-ribbon down into the body of the creature inside, and draws it back again. As it does so, of course the hooked teeth tear away little bits of the victim's flesh. The borer swallows these, and then pokes down its tooth-ribbon once more. And so it goes on, over and over again, until the shell of its victim has been completely emptied, when it goes off to look for another.
Periwinkles
These are common on rocky parts of the coast, and you may find them crawling about on the weed-covered rocks in thousands when the tide is out. They have tooth-ribbons just like that of the borer, but they do not use them in the same way, for they feed only upon seaweeds. And they are remarkable for having the foot divided by a kind of groove, which runs right down the middle. When a periwinkle crawls, it moves first one side of this foot forward, and then the other side, so that although it has no legs it may really almost be said to walk.
The Cowry
One of the prettiest of the gastropod shells, is that of the cowry, in some parts of Africa used as money. It would seemstrange to earn one's living just by picking up money on the sea-shore, wouldn't it? And perhaps you might think that every one who lived near those parts of the coast where cowries are found must be very well off. But then sixteen hundred of these shells are only worth about a quarter of a dollar, so that you would have to hunt for a very long while and stoop a great many times in order to obtain sufficient even to buy food. And it must be very awkward to have to carry several sacks of money when one goes out marketing! Many of them, however, are extremely beautiful.
Limpets
Commoner still are the limpets, which you may find in thousands clinging to the rocks that are left bare when the tide goes out. They fasten themselves down by means of the broad, fleshy foot, which acts as a big sucker. And so firmly do they hold that it is almost impossible to pull them away.
After a time, the edges of a limpet's shell cut a circular groove in the rock to which it clings, so that even the sea-birds cannot drive their beaks underneath and force it from its hold. And though, when the tide is up, the mollusk will wander to a distance of two or even three feet in search of food, it always seems to return to its resting-place before the retreating waves again leave the rock uncovered.
Amphineurans
This order of mollusks contains the curious creatures which are known as chitons. These may be described as sea-armadillos, for they are covered with a kind of shelly armor, consisting of a series of plates, and can roll themselves up into balls, in order to protect themselves from the attacks of their enemies.
One of these mollusks is called the prickly chiton, because it is covered all over with sharp spines, like a hedgehog. It grows to a length of nearly six inches. But long before it reaches its full size the spines are rubbed off, so that a large example ofthis creature is nearly always perfectly bare. The chitons live among muddy rocks at low-water mark, and are not common outside the tropics or in shallow water.
The order of the amphineurans is quite a small one, and so is that of the scaphopods, which consists only of the tooth-shells, which are very common on the sandy coasts of the Northern Pacific, and look rather like very tiny elephants' tusks. The Indians of the Puget Sound region used to string them as ornaments, and valued them highly.
Bivalves
The order of the bivalves is a very large and important one. All these creatures have their shells made of two parts, or valves, which are fastened together by means of a hinge. They have no heads, and the mantle forms a kind of flap on either side of the body. They are found both in fresh and salt water. Every one knows the "fresh-water clams," or mussels, which abound in our lakes and rivers. In the central and southern parts of the United States they are exceedingly numerous and of many kinds, some rough, others smooth. All are lined with mother-of-pearl, and pretty buttons and other ornaments are made from them. Moreover, pearls are very frequently discovered inside their shells, and sometimes they are of great value.
The Pearl-Oyster
Pearls are obtained chiefly, however, from the pearl-oyster, which is found in warm seas in many parts of the world, the principal fisheries being in Ceylon, the Persian Gulf, the South Sea Islands, and off the northeast coast of Australia. They are deposited by the mantle, and it is most likely that they are really due to a grain of sand, which has lodged inside the shell and set up irritation. Indeed, it has been found that if small objects, such as tiny stones, are forced between the valves of one of these oysters, they become covered with layers of pearl in a very short time. The best mother-of-pearl is also obtained from the shells of the pearl-oyster.
Oysters
The ordinary oyster belongs to another family of bivalves, in which one part of the shell is a good deal larger than the other.
The early life of this mollusk is very curious. The spawn is known as spat, and is produced in enormous quantities. This spat looks at first like very fine gray dust, and remains for some little time within the shells of the parent. But one day in early summer the oyster opens its valves a little way, and squirts it out like a cloud into the water. For a few weeks the little oysters are able to swim, and they generally travel backward and forward with the tide. But after a while they attach themselves to some object at the bottom of the water, and there they remain without moving any more for the rest of their lives.
One would think that, since a family of oysters is so enormously large, these creatures must be the most plentiful mollusks in the sea. But by far the larger number are destroyed by other creatures before they are able to settle down; while even after that they have a great many enemies. We have already told you how mischievous starfishes are in the oyster-beds. Then borers and dog-whelks are almost equally troublesome, and besides these there is a curious kind of sponge, called the cliona, which burrows into the shells of the mollusk and gradually destroys them, sometimes actually causing them to fall to pieces.
Black Mussels
Two or three kinds of black mussels live in vast numbers on almost all coasts, clinging to rocks and submerged timber. The way in which a mussel fastens itself to its hold is very curious, for instead of turning the whole of the foot into a big sucker, as the limpet does, it spins a number of very strong threads from that part which lies nearest to the hinge; and every one of these threads is separately fastened to the support, so that the creature is moored down, as it were, by a kind of cable. These threads are known as the byssus, and hold so firmly that it is not at alleasy to pull them away. Some of these mussels are good to eat, but are not as much used in the United States as in Europe.
The Cockle
This is another very well-known bivalve. Its heart-shaped shells, covered with low ridges, you must know by sight. It is one of the burrowing mollusks, spending its life buried in sandy mud. It is especially common at the mouths of large rivers, where enormous quantities are collected to serve as human food. And its large muscular foot is not only used in digging, but also enables it to leap to a considerable height. It is to this family that the quahog or hard clam of our markets belongs.
Razor-shells
These, too, are inhabitants of the mud, and if you want to find their burrows all that you have to do is to visit a patch of sandy mud when the tide is out, and stand quietly watching it. Before long you are sure to see a little jet of water spurt out of the mud to a height of three or four inches. Now this water has been squirted out of the siphon-tubes of a razor-shell, and if you walk to the spot, treading very carefully, you will find a tiny hole in the mud. This is the entrance to the burrow, and if you want to get the animal out, the best way to do so is to drop a little salt down the hole. For it is a very strange fact that although the razor cannot live in mud at the bottom of fresh water, it does not like pure salt at all, and is sure to come up to the surface and try to get rid of it. But if you fail to seize it at once it will retreat to the very bottom of its burrow, and no amount of salt will persuade it to come up again. The soft clam, which is sold in our markets in such enormous quantities, is a near relative of the razor.
The Piddock
One of the most wonderful of all the bivalves is the piddock, as it is a boring mollusk, living buried in the solid chalk or limestone.If you should examine the rocks which are left bare at low water along the shore of the Mediterranean, or some other warm sea, you would often find that they are pierced by numbers of rather large round holes. These are the entrances to the burrows of piddocks; and if you could split the rock open you would find several of these creatures lying in their tunnels.
Sometimes, when they are boring, their burrows become choked up behind them with the material which they have scraped away. Then they just squirt out a jet of water from their siphon-tubes, and so wash the passage clear.
It is really owing to the work of the piddocks that chalk and limestone cliffs are so much cut away by the sea. The waves by themselves can do very little in this way. For when they wash up against the face of the cliff they leave the spores of seaweeds behind them; and these very soon grow and cover the whole surface with a mantle of living green, which almost entirely prevents the cliff from being worn away. But the piddocks drive their burrows into the rock just below the surface of the water, boring backward and forward till it is completely honeycombed by their tunnels, which only have just the thinnest of walls left between them. Then the sea washes into the burrows, and breaks these walls down, so that the whole foundation of the cliff is cut away. Very soon, of course, there is a landslip, and hundreds of tons of chalk or limestone, as the case may be, come falling down. Then the piddocks begin working again a little farther back, and the process is repeated; and so on over and over again.
On many parts of the south coast of England long stretches of rocks run ever so far out into the sea, and are only partly left bare at low water. Those rocks were once the bases of cliffs, which the piddocks and the waves together have cut away. And it even seems almost certain that the Strait of Dover was cut in this manner, and that if it had not been for the labors of the piddocks, carried on day after day for thousands upon thousands of years, Great Britain even now would not be an island, but would still form part of the continent of Europe, as we know that it did in ages long gone by!
The Teredo
There is a bivalve mollusk which burrows into submerged timber, such as the hulls of wooden ships, or the beams of piers and jetties. This is called the teredo, or ship-worm, and certainly it does look much more like a worm than a mollusk, for it has a cylinder-shaped body something like a foot in length, with a forked tail, while the shell only covers just a little part at one end. How it burrows into the wood nobody quite knows. It is generally supposed to do so by means of the foot. But in a very short time it will honeycomb a great beam of timber with its burrows, which it always lines with a kind of shelly deposit, weakening it to such a degree that at last it gives way beneath the slightest pressure.
Like a great many other mollusks, the teredo passes through a kind of caterpillar stage before it reaches its perfect form. While it is in this condition it is able to swim freely about in the water, and looks rather like a very tiny hedgehog, being almost globular in shape, and covered all over with short projecting hairs. It is by means of the action of these hairs upon the water that it is able to swim.