ghtly that it is almost
impossible to get him out except by breaking the shell. Very often these
crabs are to be found with a colony of living polyps growing on their
shells. These polyps are very interesting from the fact of their being
the parents of one of our most beautiful jelly-fishes.

[Illustration: HERMIT-CRAB OUT OF SHELL.]

When a hermit-crab grows too large, or so fat that his shell pinches
him, he hunts up a new one. First he pushes his long claws far into it,
just to see that no one is inside, and that it is nice and clean; then
he rolls it over and over, often lifting it so as to judge of its
weight. If it suits, he drags it close to the entrance of his old home,
and in an instant he has whisked into his new house. Hermit-crabs are
great house-hunters, often moving just for the fun of it. They are
always skylarking with one another like monkeys, and, in truth, they are
the monkeys of an aquarium. When the water in an aquarium becomes bad,
they are sure to indicate it by leaving their shells, and trying to
crawl out of the tank. In all respects they are the most valuable and
interesting inhabitants of the aquarium.

[Illustration: PIPE-FISH.]

Pipe-fish are apt to be delicate; still, if your aquarium is in perfect
health, and the water is teeming with minute animal life, they will get
along nicely. Their favorite food consists of the eggs of all small
crustaceans, such as shrimps, sand-hoppers, and lady-crabs. Mrs.
Pipe-fish does not take care of the children, but Mr. Pipe-fish places
them in a long folding pocket that runs along the under side of his body
(which I have tried to show in the engraving). When he lets them out of
this pocket into the vast ocean world to shift for themselves, they are
only a quarter of an inch long, no thicker than a bristle, and almost
transparent.

[Illustration: DANDY-CRAB.]

Think of a crab decorating himself with bright-colored sea-weed, so that
he is called the dandy-crab! Still, he is not so vain, after all, as he
covers himself with sea-weed that he may escape the sharp eyes and sharp
teeth of hungry fishes. I once had a dandy-crab whose back I had
scrubbed clean, after which I placed him in an aquarium containing a
plain sand bottom. In this tank I also placed a hungry black-fish, who
soon took a nip at him, securing only one of his legs. This so
frightened the dandy-crab that he began searching over the aquarium for
material to cover himself with. In the tank