a brook, you will find it difficult to prevent
the escape of the fry when hatched, and you are left in doubt as
to the success of your experiment. With spring water all these
inconveniences are avoided. But if your watercourse should contain
water-lice or aquatic larvae, it is a very easy matter to destroy
them before putting in your boxes, with a little salt or
quicklime. It is also desirable to cover your spawning-boxes with
a wire grating, to exclude the light, and to protect them in
severe weather from the chance of being frozen.

When they begin to hatch, open a communication between the boxes
and the little reservoir below, and if this communicates with a
watercourse in which aquatic plants are growing, so much the
better. The fry, as soon as they are strong enough, will make
their way into this ditch, and will find abundance of food among
the water plants; thence they ought to be able to make their way
into the brook, river, or lake which it is intended to store with
them. All ducks, wild and tame, should be driven from this ditch,
or few of the Trout will be allowed to find their way to their
final place of destination.

These rules, with some modification, are applicable to the
breeding of Salmon as well as Trout; the only difference being in
the mode of placing the female fish, when obtaining the roe, and
the size of the gravel in which the spawn is deposited in the
boxes. The Salmon is too large a fish to put into the vessels in
which the diluted milt is placed, but I think that she should be
held by an assistant, in such a manner that the tail and lower
part of the body up to the vent are immersed in the water
containing the milt. And it is also very necessary to hold her
firmly, otherwise a large fish, in the struggles which it makes to
get free, is apt to upset the vessel containing the milt, and then
the experiment is at an end, at least for the time. Being held
firmly by the assistant, as above stated, the belly of the fish
must be gently pressed by the hands to promote the exclusion of
the spawn, which on exclusion must be gently stirred in the
diluted milt, to bring every grain into contact with it; but the
roe ought not to remain in contact with the milt a minute, if it
can sooner be got out, as I have found that if the diluted milt be
too strong, or if the ova remain too long in contact with it, they
become opaque, and never hatch at all, apparently because they are
over-impregnated. In the ordi