The How and Why Library/Life/Animals-Section III
III. A Sea Flower That Eats With Its Petals and Moves When It Wants To
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The sponge, the jelly fish and the coral builder are hollow-bodied animals. They are higher than the amoeba because they have more different parts. The locomotive is a higher order of machine for moving things than baby brother's go-cart. So, the sea-anemone is higher than the sponge. It is very puzzling, but you like to study puzzles and find the answers, don't you?
Here's puzzle number one: Does the sea-anemone look most like an animal or a vegetable? You will see from the picture that the answer is very easy. But—
Why does it look so much like a vegetable? Well, why do your own lungs, that you breathe with, look like a vegetable?
Your lungs are shaped a good deal like a tree with trunk, limbs and branches; and, we might almost say, twigs and leaves. The lungs are spread out in this way to get the oxygen from the air that you breathe. The lungs digest air as your stomach digests its food. Because the air is not so solid as the food your stomach digests, it takes a good deal more of it for the lungs to get the amount of oxygen you need. So they are spread out to catch as much of this oxygen as possible every time you breathe. Leaves are the lungs of the plant. There must be a great many of them, and they must spread out to take in enough air and sunshine.
If you lived in the water all the time, as the sea-anemone does, and had to get oxygen out of the water, and had no special place inside of you in which to keep your lungs, you would have to be spread out as the anemone is, into as many branches as possible, and do all of your breathing through your skin. Then—if you were a sea-anemone—you would eat as it does. The way in which the anemone eats is something like the way in which the amoeba eats but yet is quite an improvement.
The anemone lies all spread out like a flower, until a fish or some other of the little animals, upon which it lives, comes swimming along. As soon as it touches the arms of the sea-anemone, which look like the petals of a flower, these "petals" close around it, just as your fingers close around an apple. They gather in the food and push it into the anemone's mouth. Then the anemone wraps its whole self around its food and shrinks up so that it looks like ateacup turned upside down. It keeps to this shape until the food is digested. The anemone's stomach is in the center of its body, but it seems to take the whole inside of the anemone to digest its food, just as it does with the little amoeba.
The anemone's stomach is one of the queerest things you ever saw. It is surrounded by little rooms that are connected with each other by two openings that we might call "windows." Each of these rooms is also connected with the stomach in the middle, and with those parts which, as you see, look like the petals of a flower, when the anemone is spread out, waiting for its food. Each of these "petals" is hollow like the fingers of a glove. The anemone not only lives surrounded by water on the outside, but it is full of water on the inside. Water is to the anemone what blood is to you; it circulates all through the anemone, and the anemone makes its petal-like fingers stand up by filling them with water. These fingers are called tentacles. When the little animals on which the anemone lives, touch one of these tentacles, the anemone forces a large part of the water out of itself, shrinks up around its food and becomes a little upside down cup of an animal, with thin walls.
The sea-anemone not only looks like the flower of that name, but it has something that reminds us of the vine called the Virginia Creeper. The anemone is fastened to a rock by a sucking disc. It holds on with this sucker a great deal tighter than the vine clings to a wall it is climbing, with its little sucker feet. If you try to pull a sea-anemone up, you might think it has a strong root running down into the rock. But it has only a sucker foot for clinging. Sea-anemones have been known to move, but as a rule they spend their lives contentedly, fastened to rocks near which they are born.
This use of a sucker foot by the sea-anemone and the vine, is one of the many cases in which nature gets hold of a good idea and uses it over and over again. And she uses the sucker foot for plants and animals just as she uses the seed or egg for ferns and fishes, butternuts and butterflies. She gave the sea-anemone a sucker foot because he can get along best by clinging to a rock, and she gave the vine sucker feet to climb rocks and trees with. When the sucker foot idea once got into the two families of living things, Mother Nature seemed to say:
"Now all of you children who can use it, may have this little sucker foot."The oyster and the clam both have a sucker foot. The oyster uses his to fasten himself to something, as the anemone does, and stays there. But the clam uses his foot for travelling. So, the oyster, lying in one position, gets a shell that looks lop-sided, but the clam's shell has both valves alike. People who live by themselves, in one place, get one-sided, too. Instead of saying "don't be a clam" we ought to say, "don't be an oyster." The clam is well-balanced. A man is well-balanced who can see both sides of a question.
My! My! Here we have wandered away from the sea-anemone looking at vines, clams and oysters, seeds and travelling minds, and almost have forgotten our little sea-anemone! But here he is sticking patiently to his rock. Perhaps he has other things to tell us.
"Yes, indeed," he says. "When you were speaking of sucker-feet you didn't mention the fact that I had them long before there were sucker mouths. And how would human and some other animal babies get along without those, I'd like to know. You smack your lips over something good, don't you? And you pucker it to kiss with, too. I taught you how. I pucker my sucker foot to cling with."
"And I taught birds to lay eggs. Well, I'm ready to admit that the sponge taught me."
Anemones, like the sponges, make eggs, or seed babies. These eggs hatch into odd little animals that, for awhile, swim about in the water. They finally settle down on a rock, and grow into these beautiful flower-like animals that are found in the gardens under the great waters of the world. You can see that the anemone, which is so much higher a type than the sponge, at the same time repeats the habits of the sponge in first being a free, swimming animal, and then settling down in one spot. The anemone, however, can move about a little while, but the sponge cannot. After it once settles down the sponge must stay there for life. The anemone can move only a few inches a day; so I suppose it says, "Oh what's the use," and generally it stays in one place.
But, low down as it is in the scale of life, like the jelly fish, the anemone has learned how to move. So, it begins to foretell the wonderful animals that are coming, that can swim in the water, fly in the air, and finally run about on the land. And that's foretelling little boys and girls, you know.
My! But wasn't it a tre-mend-ous thing for a little sea-anemone to let go of the rock and move, if ever so little a way? See Sea-Anemone, page 1712.