correspond to our legs and arms. The nerves run along each ray. At the tip of each ray is a little dim eye, and a filmy covering that takes the place of an eyelid. Each ray is really a branch of the stomach. Little canals run from the stomach, which is in the center of the starfish's body, out to the end of each ray.
The starfish can move each ray separately, just as you can move each of your legs or each of your fingers. In this way the starfish is able to travel much faster than you would imagine.
Another member of the great hollow-bodied family, to which you, too, belong, is the sea urchin. In the water, these sea urchins look like round pin cushions stuck all over with black pins, with the points on the outside. When you find them on the sea beach, with all their spines gone, you think them a kind of sea shell. These "pins" are to protect the sea urchin against its enemies. They branch out in every direction like the bayonets of soldiers. That spine armor idea was so good, that Mother Nature used it for the porcupine, and for the thistle and the rose. The sea urchin uses these pins to walk with but, although they have between three and four thousand of these pin feet, they get along very slowly. Whenever we make a specialty of anything we can always do it better. It is when animals come to have two feet, as in the case of man or the ostrich—or four feet, as with squirrels—that they can run and climb trees and build houses and do other things that the sea urchin never even dreams of.
The sea urchin lays eggs, and from these eggs come the young urchins. (What other animal have we already found, that lays eggs?) When they are babies they don't look a bit like their parents. And here is another thing that the sea urchin does that you will remember when we come to kangaroos. Some of the sea urchins carry their babies in pouches. They fold their spines over their babies just as you carry a doll in your arms.
Do you remember, among the strange things that happened in "Alice in Wonderland", that there was a cat that faded and faded away, and left nothing but the grin? You have seen a great many cats without a grin, but a grin without the cat really seems improbable. But this—that I am going to tell you—has happened, not once but many times; no doubt millions of times:
An animal has faded away and left nothing but its mouth! This animal is called the sympata, and is a member of the sea cucumber family. Whenever this animal fails to get food for some time, it
