yet soft
he grows quickly. When it is hard, he ventures out again, ready to
quarrel and fight.

This change of shell happens often to young Crabs. Older ones change
only once a year. All the different kinds of Crab begin life as _larvae_
or _zoeas_, and cast their shells as we have seen.

Crabs can see and hear and smell; and they must also have a fine sense
of touch. I was once watching a big Crab eating his dinner under a rocky
ledge in a large glass tank. As he tore his food, some of the bits, no
larger than crumbs, fell and settled on the rocks below. Then I saw that
a smaller Crab, with long pincers, was hiding under a rock. As the
crumbs fell, he reached out his pincers and picked them up, one by one.
Each bit was gravely carried to his mouth, and tucked in, and then he
reached out for another. Though I was very close to the Crab, I could
hardly see the tiny scraps which he was able to pick up so easily.

One of the strangest Crabs is the Hermit. You would think that Nature
had played a joke on him, for he has only half a suit of armour. His
tail part is soft. He would have a bad time in the sea, but for a dodge
he has learnt.

The baby Hermit takes the empty home of a periwinkle. As he grows he
needs a larger house, and so leaves the tight shell and pops his tail
into a bigger one, generally a whelk shell. If he meets with another
Hermit there is a battle, one trying to steal the other's shell. Our
coloured picture, page 35, shows some Hermits at war. Fighting,
house-hunting, and moving house seem to be the Hermit's favourite
pursuits. But, whatever he does, his first care is to protect that soft
tail of his. His right claw is large and strong, so he uses it to close
the door of his stolen home.

Sometimes he has a lodger who lives on the roof. This lodger, as you
will notice in our coloured picture, is the sea anemone. The Hermit and
his lodger seem to be good friends, at least they seem to like each
other's company. There is no doubt that there are good reasons for this.
We shall have more to say about this strange pair in our lesson on the
sea anemones.

[Illustration: HERMIT CRAB IN WHELK'S SHELL.]

Another funny Crab is the Spider Crab. Its back is covered with reddish
bristles, like so many hooks. These catch in the seaweed, and soon the
Spider Crab is decorated with bits of weed. But that is not all. The
artful Crab tears off other pieces of weed with its pincers, and
attaches them to the hooks.