What fun it is down by the sea at low tide! Scrambling among the slippery rocks, we quickly fill a bucket with curious things. Some are dead, others very much alive; but all have a story to tell us—the story of the life they lead on the bed of the sea, or among the sands and rocks of the shore.
Look, here is a Starfish! It is lying on the sand, left high and dry by the waves, for now the tide is low. The Starfish looks limp and lifeless, its five reddish-coloured “arms” are quite still.
We know it is an animal that lives in the sea, and dies when washed ashore. But what does it do in the sea? How does it move without legs or fins? How can it live without a head? Has it a mouth? What does it eat, and how does it find its food?
Like so many other sea-animals, the Starfish is a puzzle. Some of its little tricks puzzled clever people until quite lately. But we know most of its secrets now.
Pass your finger down one of its arms, or rays. It feels rough, being covered with knobs and prickles. Now turn the Starfish over, and look carefully at its underside. In the centre, where the five arms meet, is the animal’s mouth. A harmless sort of mouth, you think, too small to be of much use. Really, it is a terrible mouth, the mouth of an ogre!
We notice a groove down the centre of each ray. But what are those little moving things which bend this way and that, as if feeling for something? Now that is exactly what they are doing. They are the feet of the Starfish. Each tiny foot is really a hollow tube, which can be pushed out or drawn in. At the tip of each is a powerful sucker, which acts rather like those leather suckers boys sometimes play with. Suppose the Starfish wishes to take a walk along the bed of the sea. First, it pushes out its tube-feet. Each sucker fixes itself to a stone or other object, and then the animal can draw its body along. You will see presently that the suckers can do other work too.
Our Starfish will die, however, unless we carry it to a pool. Before doing so, we must look at the tip of each ray for a small reddish spot. That is the Starfish’s eye. Are those little eyes of much use in helping the creature to find its dinner? I think not. Most likely the Starfish smells its way.
If we put the animal on its back in a rock-pool we shall see the tube-feet at work. Once in the water our Starfish revives, and makes efforts to right itself. Can it turn over and crawl away?
The little tube-feet come out of their holes and begin to bend about. Now those near the edge of one “arm” feel the ground. Each tiny sucker at once takes hold, more and more of them touch the ground as the ray is turned right side up, and at last the Starfish turns over, and, slowly but surely, glides away.
[Illustration: Common five-fingered starfish.]