may be obtained sometimes from another locality if
they cannot be got on the spot. These should be carefully preserved for
the first year at any rate, and a good fly may thus be introduced into a
water where it was before unknown.

I have already spoken of the fresh-water shrimp and the water-flea
(_Daphnia pulex_). These valuable articles of diet should be introduced
whenever it is possible. _Daphnia_ must be reared in a stagnant pond,
the fresh-water shrimp (_Gammarus pulex_) in running water, with plenty
of weeds.

Other useful creatures besides those snails and mussels which I
described in a previous chapter, are the water-louse (_Asellus
aquaticus_), _Cypridae_, and _Cyclops quadricornis_. Asellus is very
similar in size and shape to the common garden-louse, which is found in
decaying wood. It will live either in stagnant or running water.
_Cypridae_ are very much smaller, being generally only as large as a
large pin's head. They have a bivalve shell which makes them look
something like a small mussel. They are, however, very active, swimming
by means of two pairs of legs. They also possess two pairs of antennae
and one eye. (The species belonging to the genus _Candona_ of the family
_Cypridae_, do not swim.) _Cyclops_ is another very small crustacean,
shaped like a large-headed club. It swims very actively, and, like the
_Cypridae_, is an excellent article of diet for very young fish. Both
these crustacea live in stagnant water, and must, therefore, be kept in
a separate pond, whence they may be taken as required to be given to the
fry.

CHAPTER X

TROUT. MANAGEMENT, FEEDING, AND TURNING OUT OF YEARLINGS

As I pointed out to my readers in Chapter VIII., the young trout have
after August passed the critical period of their existence, and may be
considered safe and hardy. Naturally, as they get older, they require
more food, but this need not be given so frequently as the fish grow
older. While it was necessary to feed the fry at least four times a day,
it will be found quite sufficient if the fish in August are fed only
twice during the twenty-four hours. I must here again impress upon my
reader the importance of feeding the trout upon as natural a food as
possible. Their future well-being depends upon this, much more than is
generally realized even by fish culturists. Of course, trout fed
entirely upon soft food may turn out all right, particularly if they are
turned out as very young yearlings, but