LESSON XXXIII.
MR. BARNACLE AND HIS SON.
The Barnacle has a name which means hair or ringlet-footed. People thought his little fine curled-up feet looked like small curls of hair. His body is like a small bag or sac, with the six pairs of littlecurly feet placed at one end. The body is made of rings as are the bodies of insects. All the six pairs of legs are on the chest rings. Each leg has two joints, and a little branch like a fine fringe. The hard shelly cover of the barnacle is made of plates lapped together. When they are closed they look something like buds on trees, or young pine cones. When the fringes of the feet wave out between the edges of the shell-plates, it looks as if the buds were about to open into flower.
A barnacle is more like his far-off cousin Mr. Crab when he is little than when he is grown up. Every grown-up barnacle must be firmly fastened upon some other body. The barnacles are divided into two classes, according to the way in which they are fastened upon objects: 1. Stem Barnacles, 2. Stemless Barnacles.
A stem barnacle has plates which form a three-cornered shell. It grows fast to some object by a small stem which is soft, and can bend about easily.
A stemless barnacle has a shell shaped like an acorn, or like a rosebud with the top bitten off. Instead of a stem, it is held fast to the object on which it grows by a thin plate of shell at its broad, or flat end. This plate has a tiny hole in the centre.
When you first saw a barnacle, you would not think it was any relative of Mr. Crab. Whengrown up it does not look at all like the Crab Family. When crabs and barnacles are very young, they look more like each other.
Old and Young Barnacles.
Old and Young Barnacles.
Let us look at an acorn barnacle. The shell is in plates, as if two or three shells were set one over another. The shell grows by added bits of lime, as a conch shell does. The thin skin that lines it, and holds it together, is shed, like Mr. Crab’s coat. Then the shell has room to grow.
The shell is hard and white. It is lined witha very thin skin, which often has a faint, pretty tint.
The stem barnacles have long, flesh-like stems which move and sway with the motion of the water. They look much like a little, queer, pale plum hung by a thick stem.
The end of the barnacle, which clings to the stone, log, shell, or fish on which it has fastened itself, is the head end. The two feelers, which all these animals have, are turned into two fine tubes, or pipes. These feelers have little glands or sacs which make a strong cement. Cement is like glue, but much more strong and stiff.
This cement fastens Mr. Barnacle to his place. So after he has settled himself in life, he never wanders about any more.
Did Mr. Barnacle ever go abroad? Oh, yes! When he was young he swam about the water-world, in a very brisk way. Let us hear about that.
Mr. Barnacle makes the same changes of life that an insect does. First he is an egg, then a larva, then a pupa, and at last a steady old barnacle. But the larva barnacle makes two or three changes of shape before it turns into a pupa.
Barnacles grow fast. They change their coats often when they are young.
Here is an old acorn barnacle fast upon a stone.It is about as big as the end of your little finger. It has some eggs which it packs into the shape of a small leaf. It tucks this leaf of eggs into a fold of the thin skin that lines the thick shell.
As the eggs get ready to hatch into larvæ, the old barnacle is also growing, and making more shell. Soon it is ready to enlarge the outer shell. So the inside skin cracks apart and falls off. By degrees some barnacles become quite large as fresh shell grows from within.
When the old inside skin falls off, the eggs are set free. Out of them come the larvæ. The larvæ are active, hungry little fellows, who know how to swim as soon as they are loose in the water.
The larva acts as if it liked to be free from the shell prison. It darts about in the sea, and each day its shape changes. It has one eye, a mouth, two feelers like horns, and six legs. It can swim, and can walk over sea-weed.
Some parts of this gay little larva will one day turn into tubes to make cement to hold it fast to a stone. Then it will be a stay-at-home barnacle all the rest of its life long.
When the larva becomes a pupa, it drifts about until at last it is time for it to stop travelling and keep still. Then it fixes itself by its head to the place that will always be its home. All it has to do after that, is to fish and eat. As it makes new shell, it will enlarge the old shell. And it will have little eggs, packed in the shape of a wee leaf between the skin and outer shell.
By and by Mr. Barnacle has a hard shell of many plates, his eye has gone down near his stomach. Do you think he can see what he eats? His legs are not used for walking, but to fish with; his mouth is near his feet. The rest of his head has gone off with his feelers, to attend to making cement and shell. What a queer creature he is!