he ocean, and lost. The rest of them, before they have been free for
two days, settle on the bed of the sea--sometimes on their own parents;
and there they remain for life. Only a very few out of each million
become "grown-ups"--the rest are eaten by enemies, or smothered in mud
or sand. In a year or so they are as big as half-a-crown. In five years
they are fine, fat grown-up Oysters--that is to say, if they have not
been dredged up from their bed and sent to market.

Their shells open and shut like a trap. You may have seen a picture of
an inquisitive mouse trapped by an Oyster. Thinking to have a nice taste
of Oyster, the mouse had poked its head into the open shells, but they
were snapped together, and the mouse was firmly held in the trap.

Between the hinge of the two shells there is a pad, which acts like an
elastic spring, and forces the shells open. The Oyster can close them by
means of a strong muscle. They are its only defence, so it closes them
at the least hint of danger.

Even these thick walls are sometimes of no avail, as we saw in our talk
on "Five-fingered Jack." We saw how the starfish forces the shells open
with the help of its strong tube-feet. The whelk and his cousins know
how to bore a hole in the shell, and suck out the helpless Oyster. Then
there are certain sponges, with the strange habit of making holes in
shells, and living in and on them. Sometimes the Oysters are stifled in
their "beds" by other Oysters settling and growing over them. Thick
masses of Mussels may cling to them and suffocate them. And grains of
sand sometimes get in the hinges of their shells, so that they cannot
close up the house when they wish.

Like the other animals which are useful as food, Oysters have been
carefully studied and cultivated by man for many, many years. The story
of the Oyster-beds is a long and interesting one.

Oysters feed in rather a strange way. You may have looked inside the
shells and seen two delicate dark-edged fringes, known as the "beard."
This fringe is the Oyster's gills or breathing arrangement. Trace the
"beard" as far as the hinge of the shells, and you see the mouth with
its white lips. If you could watch the creature having its dinner, you
would see a constant stream of water flowing over the gills and towards
the mouth.

What makes the water move in that way? The gills are covered with very
tiny lashes, like little hairs. There are so many of them that, as they
keep moving, they