“Don’t you know, Poll?” said Edwin; “why, I thought your father taught you about almost everything.”
“Oh no,” replied Polly, with an innocent smile, “not everything yet, you know, but I daresay he will in the course of time. Tell me about the insects.”
“Well, let me see, how shall I begin?” said Jack, leaning against the bank, and crossing his arms on his breast. “The coral insects, Polly, are very small, some of them not larger than a pin’s head. They are great builders. There is lime in sea-water. The insects, which are called corallines, have the power of attracting this lime to them; drawing it away from the water, so to speak, and fixing it round their own bodies, which is called secreting the lime. Thus they form shells, or houses, to themselves, which they fix at the bottom of the sea. Having laid the basements of their houses close together, they proceed to add upper storeys, and thus they add storey to storey, until they reach the surface of the sea. They work in such innumerable millions that, in course of time, they form reefs and islands, as you see.”
“But I don’t see!” said Polly, looking round; “at least, I don’t see corallines working.”
“Ah, good,” said Baldwin, with a nod of approval to the child, as if to say, “You have him there!”
“True,” returned the philosopher, “because the corallines can only work under water. The moment they reach the surface they die; but those that remain continue their labours on the sides of the reef or island, and thus widen it. Then the waves break off masses of coral, and cast them, with drifting sea-weed and other things, up on the reef, which makes it higher; then sea-birds come to rest on it. The winds carry seeds of various plants to it, which take root, grow up, die; and thus thicken the soil by slow degrees, till at last, after a long, long time, the island becomes a pretty large and fertile one like this.”
“Wonderful!” exclaimed Polly; “what a clever insect!”
“Clever indeed,” returned Edwin; “especially when we consider that it has got no brains.”
“No brains!” echoed Baldwin.
“No, it has little more than a stomach.”