have changed during the last forty years.

We used to find them sometimes washed up among the sea-sand on the wild
Atlantic coast; and we were taught, in the days when old Dr. Turton was
writing his book on British shells at Bideford, to call them Nautili,
because their shells were like Nautilus shells. Men did not know then
that the animal which lives in them is no more like a Nautilus animal
than it is like a cow.

For a Nautilus, you must know, is made like a cuttlefish, with eyes, and
strong jaws for biting, and arms round them; and has a heart, and gills,
and a stomach; and is altogether a very well-made beast, and, I suspect,
a terrible tyrant to little fish and sea-slugs, just as the cuttlefish
is. But the creatures which live in these little shells are about the
least finished of Madam How's works. They have neither mouth nor
stomach, eyes nor limbs. They are mere live bags full of jelly, which
can take almost any shape they like, and thrust out arms--or what serve
for arms--through the holes in their shells, and then contract them into
themselves again, as this Globigerina does. What they feed on, how they
grow, how they make their exquisitely-formed shells, whether, indeed,
they are, strictly speaking, animals or vegetables, Analysis has not yet
found out. But when you come to read about them, you will find that
they, in their own way, are just as wonderful and mysterious as a
butterfly or a rose; and just as necessary, likewise, to Madam How's
work; for out of them, as I told you, she makes whole sheets of down,
whole ranges of hills.

No one knew anything, I believe, about them, save that two or three kinds
of them were found in chalk, till a famous Frenchman, called D'Orbigny,
just thirty years ago, told the world how he had found many beautiful
fresh kinds; and, more strange still, that some of these kinds were still
alive at the bottom of the Adriatic, and of the harbour of Alexandria, in
Egypt.

Then in 1841 a gentleman named Edward Forbes,--now with God--whose name
will be for ever dear to all who love science, and honour genius and
virtue,--found in the AEgean Sea "a bed of chalk," he said, "full of
Foraminifera, and shells of Pteropods," forming at the bottom of the sea.

And what are Pteropods?

What you might call sea-moths (though they are not really moths), which
swim about on the surface of the water, while the right-whales suck them
in tens of thousands into the great whalebone net w