Each case, or pocket, is flat, and has a rim. The rim has lines in it. In the front edge is a small, round spot, where the case is very thin. This is the door of the case. The sides of the case are very tough. Let us cut one case open. It is full of white gum, or jelly. I see in it specks like grains of sand. Here is one more string, far up on the sand. This one is dry, hard, and light. The little thin places are real holes now. The cases are quite empty. Here is one more string. This, too, is light and dry. But the holes in front are not open. Shake it. Does it rattle? Yes. Cut a case open. Why! Each case is full of wee shells! Each shell is as small as a grain of rice! See how thin and white these shells are. LESSON XXXVII. MORE ABOUT SEA-BABIES. Now in these strings you have the whole story. First, the tiny string Mrs. Conch left on the sand grew to be a big string with large cases like these. The small specks in it were to become shells, and the jelly was to be the food of the baby conchs while in the case. There are very many in each case. They grew and grew. They ate up all the jelly. They were true shell-fish, only very small. Then it was time for them to go out. They saw the thin skin over the small, round hole. They felt sure that this was their door. They ate off the thin skin, and went into the sea. The conch lays its egg-strings from March to May. It lays a great many. In the egg-case the baby shells rock up and down, not on a tree, but on the sea. This dry string, still full of shells, is one in which the shells are all dead. It was cast on shore when the little fish were too young to come out. That made them all die. These little things have a hard time to grow up. But if they can live until they are of a good size, they will have a thick shell. Then they will be out of harm’s way, and will live a long time. But how do these shell-fish grow? Do they pull off their shells when they are too tight, as crabs do? No. All these shell-fish wear a cloak, or veil. It is by their cloak they grow. Why, how is that? This cloak, or veil, is fine and thin. It is part of the body of the fish, and folds all over it. This fine cloak takes lime out of sea-water, and with it builds more shell. As the animal needs more room, it spreads out this veil over the edge of the shell, and builds with it new shell. You can see the little rims where the cloak built each new piece. The color and the waved lines on the shell are made by this veil. So the shell-fish need not change his house. He just builds on more room as he wants it. LESSON XXXVIII. ABOUT MR. DRILL. Here is a small shell-fish. He looks like Mr. Conch, but is not so large. He is quite small. His real size in the sea is not much larger than he is in this picture. His name is Mr. Drill. [Illustration: THE LITTLE ROBBER.] His color is dark brown. His shell has ridges on it. The body of the drill is dark green. It has a long tail to twist round in its shell.