, unventilated room; and if the supply should
become too small, the fish will die, just as we should die in a room
where no fresh air could enter. So the fish must have the water changed
unless there is enough plant life in its tank to keep the air pure. When
suffering for air, the fish shows signs of distress, which should never
be ignored. If it keeps close to the surface of the water with its mouth
up and frequently swallows the outside air, that is a sign it needs
fresh water. If it does not have it after a while it will die, as it
cannot live on air undiluted by water.

Fishes need very little feeding, particularly if there are water plants
in the tank; they find food from them. The best way is to follow the
directions of the man who sells you the fishes. If too much food is
given them it quickly fouls the aquarium, and then the water must be
changed and everything cleaned up. In changing the water, care should be
taken to have that which is put in about the same temperature as that
taken out. A sudden application of too cold water is not good for the
fishes. The children should take care of their pets themselves and see
that they do not suffer.

The motions of the fish are what make it so attractive. How does it
swim? Not with its fins to any extent. The whole back part of the body,
including the tail, is moved from side to side as the fish swims. It
moves its tail as a paddle is used at the stern of a boat, and so the
fish paddles himself along. The fins are used more as balancers. They
keep the fish upright in the water. As soon as it stops using them, it
turns over on one side.

The fish opens and shuts its mouth constantly; it appears to be
swallowing water. And so it is, so far as its mouth is concerned, but
the water it takes in does not go down into the stomach. It is not
really swallowed, but passes out at the gills, which are also constantly
opening and shutting. The gills are red inside and are covered with a
fine network of blood vessels. The air in the water moves against these
delicate blood vessels, which are able to take what they need--the
oxygen--from it. Thus the fish uses gills instead of lungs for
breathing.

Sometimes, fishes pick up pebbles in their mouths and drop them again.
Some fishes, but not goldfishes, make noises.

The adaptation of the fish to its surroundings is interesting. Not only
is its form the very best for moving quickly through the water, but its
covering is peculiarly