THE SHRIMP.

Some are Shrimps, and some are Prawns; how can we tell the difference? When they are boiled the answer is easy. All the Shrimps turn brown and the Prawns red. (The red "Shrimps" are near relations of the Prawn.) To tell a live Shrimp from a Prawn, look at the long pointed beak which juts out from the front of the head. That of the Prawn is toothed, like a little saw. If the beak is quite smooth its wearer is a Shrimp.

Until Prawns are grown up, they haunt the sandy shallows with their cousins the Shrimps. But the larger Prawns live in deeper water. They are generally caught in traps, as are their relatives, the crab and lobster.

Now look closely at a Prawn, and try to find how it swims. Turn it upside down. It has ten legs; and, under each of the horny rings of its body, you can see a pair of little paddles. They are fringed with hairs. When the Prawn or Shrimp is not in a hurry, he swims slowly but surely with the little paddles, or "swimmerets." If any danger threatens, he uses his tail, in this way:--It is made of five fringed plates, which, as you can see, spread out or close up, like a fan. As he doubles up his body, the plates spread themselves out. They strike the water with great force, and so send the Prawn or Shrimp quickly backwards. As the body becomes straight again, the fan closes, ready for another stroke. To move quickly, the Shrimp or Prawn merely bends his body, then straightens it. The tail thus becomes a strong oar, driving him backwards with rapid jerks.

Look now at the Prawn's long, hair-like feelers. There are two pairs. On one pair are the ears, a special kind of ear for hearing in water.

You will notice that the Shrimp's eyes are on the end of short stalks. Each big eye is really a cluster of little eyes, rather like the "compound eyes" of insects. If you lift up the horny shield behind the head, you see a row of what look like curly feathers. These are the breathing gills.

Shrimps carry their eggs about with them; no doubt you have often found masses of eggs under the Shrimp's body. Each egg is fastened by a kind of "glue," or else the rapid jerking of the mother Shrimp would soon loosen the eggs and set them free.

The hard, shelly covering of the Shrimp and Prawn is like the armour of the crab--it will not stretch in the least. The body is easily bent, owing to the soft hinges between the hard rings. But the coat itself will not stretch. Then how do these little creatures grow? We see small Shrimps and large ones, so grow they must, in some way.

They are of the same family--the crustacea--as the crab; and they grow in much the same way. The hard covering gets too tight for the body inside it. Then it splits across the back. After much wriggling, the Shrimp appears in a new soft skin. While the skin is still soft the Shrimp grows very quickly. Crustaceans have a funny way of growing, have they not? Instead of growing evenly, little by little, they grow by "fits and starts," a great deal in a few hours and then not at all.

Besides being good food for us, and for the fish, Shrimps and Prawns have another use. They are scavengers. They pick to pieces and eat the vegetable and animal stuff which floats in the sea. Before it can decay and become poisonous, these useful creatures use it up as food. Great numbers of Shrimps and Prawns are caught for our markets. Some are caught by men who push a small net over the sands near shore, but most are caught by the shrimp-trawl, a large net cast from a small sailing vessel.

The rocks, and the wooden piles of the pier, are often covered with the hard shells known as Barnacles, or Acorn Shells. If you slip on them with bare feet their sharp edges cut you. Each Acorn Shell is a little house. Have you ever caught a glimpse of the animal living inside?

If you will look very carefully, you will see that the Acorn Shell is made of three-sided pieces, closely joined. There is a little door at the top, kept tightly closed until the tide comes up and covers the rocks. Then watch, and you will see a bunch of tiny feathers appear through a slit in the door. This means that the animal is hungry, and has put its twelve legs out of doors to catch a dinner!

This is strange, but true! The Barnacle is always upside down in its home, and its twelve feathery legs are thrust out of the door at the top. They make a fine net, in which minute animals are caught and brought into the mouth below. This funny creature actually kicks its food into its mouth! If you own a magnifying glass, you can see this for yourself at the seaside.

You will not be able to see the mouth, however, which is inside the shell. It is fitted with moving parts, and feelers, like the mouth of a crab. Also, the Barnacle has a good set of teeth to grind its food. It has no real eyes, having no use for them. Of what use are eyes to an animal standing on its head in a small dark shell! Now and then it casts its coat (like the Crab and Shrimp). The old coat is rolled up and thrown away outside the door.

Now comes the strangest thing of all. As a baby, the Barnacle is a free swimming creature. It has three pairs of legs, a tail, a useful mouth, and one eye. After kicking about in the sea for some time, and changing its skin, it changes its shape entirely. It now looks more like a tiny mussel. It has two little "shells," two eyes, legs, and feelers. Now its swimming days are nearly over, and it must settle down. It gives up eating, and roves about looking and feeling for a place to settle on.

Finding a suitable spot, the little animal stands on its head. Then a kind of glue is formed, which fixes it for life to that place, head down. The two shells and the two eyes are now thrown off. The Barnacle quickly builds up a shelly house, and, after a life of adventure and change, becomes a fixed Barnacle for the rest of its days.

For many years people knew little of this strange animal. All its wonderful changes, and the way its body is made, tell us plainly that the Barnacle is actually first cousin to the Crab, Lobster, Shrimp and Prawn! It belongs to the class known as the Crustacea; but, for some reason or other, it has chosen to live its grown-up life fixed to a rock.

EXERCISES

1. How does the Shrimp swim?

2. Of what use are Shrimps and Prawns in the sea?

3. How can you tell a live Shrimp from a live Prawn?

4. How does the Barnacle obtain its food?

5. Give the names of five crustaceans.