Those which helped to make this bit of stone are called coral-insects: but they are not really insects, and are no more like insects than you are.
Coral-polypes is the best name for them, because they have arms round their mouths, something like a cuttlefish, which the ancients called Polypus.

But the animal which you have seen likest to most of them is a sea-anemone.
Look now at this piece of fresh coral--for coral it is, though not like the coral which your sister wears in her necklace.

You see it is full of pipes; in each of those pipes has lived what we will call, for the time being, a tiny sea-anemone, joined on to his brothers by some sort of flesh and skin; and all of them together have built up, out of the lime in the sea-water, this common house, or rather town, of lime.
But is it not strange and wonderful?
Of course it is: but so is everything when you begin to look into it; and if I were to go on, and tell you what sort of young ones these coral-polypes have, and what becomes of them, you would hear such wonders, that you would be ready to suspect that I was inventing nonsense, or talking in my dreams.

But all that belongs to Madam How's deepest book of all, which is called the BOOK OF KIND: the book which children cannot understand, and in which only the very wisest men are able to spell out a few words, not knowing, and of course not daring to guess, what wonder may come next.
Now we will go back to our stone, and talk about how it was made, and how the stalked star-fish, which you mistook for a flower, ever got into the stone.
Then do you think me silly for fancying that a fossil star-fish was a flower?
I should be silly if I did.

There is no silliness in not knowing what you cannot know.