V. Starfish, and Sea Urchins That Play With Live Dolls
Animals like the sponge and the sea-anemone rank higher in the scale of life than the amoeba because they are hollow-bodied. The next higher step is taken by the group of animals to which the starfish, the sea urchin and the sea cucumber belong. They may be said to have real stomachs. The sponge and the anemone only have a special place in the body set apart for digesting food.
Of course there are many strange and interesting things about these animals as there are about everything in the great book of nature, when you come to look at it closely. Probably the amoeba doesn't have as much trouble with his stomach as you do sometimes when you eat more than you should; for if the part of himself he happens to use for a stomach today gets out of order, he can use the other side of himself for a stomach tomorrow, and so give today's stomach a rest. That is the best thing a boy can do for his stomach when it gets out of order. Give it a rest. But the sea cucumber can throw away its stomach and grow a new one.
sea-cucumber
A sea animal which seizes its food with the long tentacles seen at top of picture. Through these it breathes also. It moves by the tubes or feet seen on the body, which when filled with water act as suckers and drag the animal over the bottom.
The starfish belong to the spiny-bodied group. They are higher than the sponges and animals of that class, not only in having stomachs more like ours, but in other ways. They are the first animals that begin to walk on solid ground. This they do by forcing water into the suckers with which they get their food. When the suckers are made firm and strong by being filled with water taken into the little animal's mouth, they are firm enough to walk with. (Don't you see how in the starfish, Nature is using over again the sucker foot of the anemone, and his water-filled "petals"?)
The starfish has nerves, as we have already learned. These animals are called starfish because a great many of them are shaped like five-pointed stars. The body is in the center, and the rays
