ilt with, they had to
make their cells six-sided, like those of a honey-comb: on this account
they are called Favosites.

[Illustration]

The colony thrived for a long time, and accumulated quite a stock of
limestone. But at last a change came: there was a great rush of muddy
water from the land, and all the Favosites died, leaving only a stony
skeleton to prove that industrious Polyps had ever existed there.

This skeleton remained undisturbed for ages, until the earth began to
rise inch by inch out of the water. Then our Favosites' home rose above
the deep, and with it came all that was left of its old acquaintances
the Trilobites, who were the ancestors of our crabs and lobsters.

[Illustration: Trilobite]

Then the first fishes made their appearance, great fierce-looking
fellows like the gar pike of our lakes, but larger, and armed with
scales as hard as the armour of a crocodile. Next came the sharks, as
savage and voracious as they now are, with teeth like knives. But the
time of these old fishes and of many more animals came and went, and
still the home of the Favosites lay in the ground.

Then came the long, hot, damp epoch, when thick mists hung over the
earth, and great ferns and rushes, as stout as an oak and as tall as a
steeple, grew in Nova Scotia, in Pennsylvania, and in other parts of
America where coal is now found. Huge reptiles, with enormous jaws and
teeth like cross-cut saws, and smaller ones with wings like bats, next
appeared and added to the strangeness of the scene.

But the reptiles died; the ferns and the rush-trees fell into their
native swamps, and were covered up and packed away under great layers of
clay and sand brought down by the rivers, till at last they were turned
into coal, forming for us, what someone has called, beds of petrified
sunshine. But all this while the skeleton of the Favosites lay
undisturbed.

Then the mists cleared away as gradually as they had come, the sun shone
out, the grass grew, and strange four-footed animals came and fed upon
it. Among these were odd-looking little horses no bigger than foxes;
great hairy monsters larger than elephants, with tremendous tusks; hogs
with snouts nearly as long as their bodies; and other strange creatures
that no man has ever seen alive. But still the house of the Favosites
remained where it was.

Next came the great winter, and it continued to snow till the mountains
were hidden. Then the snow was packed into ice, and