1. THE STINGING JELLYFISH.2. THE SEA ACORN.
The fact is this. Running round the oval body of the sea acorn are eight narrow bands, and on each of these are a number of very tiny scales, placed one above another, which keep on rising and falling again, like so many little trap-doors. These scales are really paddles, by means of which the animal drives itself through the water, and as they move up and down they catch the rays of light and break them up, just like that triangular piece of glass which we call a “prism.” And though you cannot see the jellyfish itself you can see these little flashes of coloured light, and so can trace the course of the little creature as it travels slowly along.
This curious jellyfish has only two fishing-threads, which hang down from the lower part of its body. But from each of these a number of little side-threads spring out, just like the “snoods” on the lines which fishermen use in the sea. And the animal is always throwing these out and drawing them in again, so that it really “fishes” for the tiny little creatures on which it feeds.
CHAPTER IX
SEA ANEMONES
HOW SEA ANEMONES ARE FORMED
THE most beautiful of all the creatures which live in the sea are undoubtedly the Sea Anemones, which are just like living flowers of all sorts of lovely colours. But I do not know why they are called sea “anemones,” for they are much more like asters, or dahlias, or chrysanthemums.
These anemones are made in a very curious way. You will notice, as you look down into a rock-pool, that their soft fleshy arms, or “tentacles,” are all spread out like the petals of a flower. If you touch them, however, they at once come closing in and disappear, so that in two or three moments the creatures look like mere lumps of coloured jelly. But if you wait for a little while they will push out their tentacles again, and spread them just as before.
The fact is that the body of a sea anemone is a kind of double bag. Suppose you take a paper bag, twist up the mouth, and push it downwards, so that the sides of the bag surround it all the way round. You will then have two bags, as it were, one inside the other, the space between the two being filled with air. Now that is just the way in which the body of a sea anemone is formed, with this difference, that the space between the outer bag and the inner one is filled with water. It forms, in fact, a kind of water-jacket.