n nature-work these days in school and out, and
all the books written and all the stories told of living creatures of
all kinds, it is helpful and easy to linger in the delightful and
impersonal realm of the lower life yet longer, with this distinct
advantage, that the _feeling_ of universality, which is very different
from the _thought_ of it, will be strengthened.

For several reasons, the step from plant life to animal life can well be
taken by means of the fish, particularly with little children. There is
nothing prettier than living fishes in water. The fascination they have
for all conditions and ages is shown by the crowds always seen at
exhibitions of live fish in aquaria.

The child can have his little aquarium at home, which may consist of a
glass globe plentifully supplied with some pretty water weed and a
goldfish or two. Fishes do not like the bright light all around them,
and should be provided with some sort of refuge, like the water weed,
or if the tank is large enough, with stones piled up to make a cave. For
the same reason, the globe should not be set in the window or on the
middle of a small table, but should be placed where at least one side of
it may be shadowed by something. Pebbles should be put in the bottom of
the tank and not too many fishes crowded together. They need room to
move freely, and also plenty of fresh water for breathing. At the
bird-stores small aquaria can usually be bought and fitted out with the
proper amount of water plants to balance the breathing of the fishes.
For the impurity breathed out by the fish is the same as that breathed
out by all creatures, the carbon dioxide which it discharges into the
water being just what the water plant needs to grow on. Also the water
plant returns pure oxygen to the water, which is just what the fish
needs to breathe. This story of the interdependence of the two, and the
possibility of so balancing the plant and animal life in the tank that
it is never necessary to change the water, can be made very
interesting, and, needless to say, very illuminating. The fish cannot
live out of the water, and yet it breathes air. There is always air in
the water unless it has been artificially removed as by boiling, and
this little bit of air is enough for the fish, which is cold-blooded and
does not need so much fuel to keep its vital forces burning. But this
little it must have, and it will suffer for the want of it, just as we
suffer in a very close