A little pink crab, named Pea Crab, goes to live in the shell of the oyster. The oyster does not seem to mind it. You may see this little crab in your oyster soup. He turns orange color when he is cooked. Pinna, or Pea Crab has a very soft shell. The Spider Crab has a brown shell, rough like sand. Little thorns grow all over it. This Spider Crab cuts off fine sea-weed with her little sharp claws, and hangs it like ribbons on these thorns or hooks.[7] Then she looks like a little green grove! Who can tell why she does that? Is it to hide? Do you see the wide hind feet of the crab in this picture? Those are his paddles, or oars. They are his swimming feet. His shell is wide and light. He can float on the waves like a boat. He goes far out on the sea. Some crabs can dig into the sand very fast. They go in backwards. They slip out of sight like a flash. Or, they leave the tips of their heads and their eye-pegs out, to look about. Sand-crabs do this. Their shells are a pale brown or sand color. Their shells are wide and round behind, and come to a point in the front. Their heads are in the narrow part of the shell. Their shells are rough. They are swift runners. Some hide in holes in the rocks. Some are sand-color, and their color protects them. When they are afraid, they lie flat on the sand, and it is hard to see them. Some birds have long, thin bills, with which to pick Mr. Crab out of his sand house. FOOTNOTES: [7] See Picture in Lesson IV. LESSON X. THE USES OF CRABS. How often does Mr. Crab get a new coat? His coat does not wear out. But it gets too small. Then he changes it to get a larger one. The baby grows fast. You seem to see it grow. You grow fast. They say it is hard to keep you in clothes. You cannot wear the coat you had last year. But your papa can wear his coat for many years. He will tell you that he is done growing. It is so with a crab. When he is very young, he grows fast. He needs a new shell very often. When he is older, he grows more slowly. Then he gets a new coat every spring. At last he does not grow any more. He keeps the same shell,[8] year after year. It gets very hard and thick, and loses its bright color. Very often it is nearly covered with limpets. They fasten their flat or pointed shells to the crab’s back, and stay there. I cannot tell you just how long a crab lives. Of what use is a crab? Have all things a use? [Illustration: MR. CRAB HAS A PICNIC.] Yes. God made all things; and all things are of use. Sometimes we cannot find out the use. Crabs are good for food. Some kinds are eaten by men, as fish and oysters are eaten. Birds eat a great many crabs. Some birds almost live on them. Fish eat many crabs. There are many kinds of crabs so small that you could hardly see them. Fish feed on them. Men catch and eat the fish. Crabs help to keep the sea and the sea-shore clean.