e
layer. They must on no account be poured into the trays from a height.
While under water well-eyed ova will stand a good deal of gentle
tumbling about, but if dropped into the water from even a little height
the concussion is likely to kill them.

Mr. Armistead recommends glass grills rather than trays such as I have
described, but I have found the trays work very well, and they are very
simple and clean. Glass grills are, however, very excellent, though they
necessitate a somewhat greater initial outlay than do the perforated
zinc trays.

A German fish culturist has recently recommended keeping a stock of
fresh-water shrimps (_Gammarus pulex_) in the hatching trays and rearing
boxes. He says that the shrimps eat only the dead ova, and never touch
the living ones. They also eat any vegetable or animal _debris_. I have
never tried the experiment myself, and so cannot speak from experience.

Dead ova should be always removed at once, and the hatching trays should
be gone over carefully once or twice a day to see if any are present in
them. Dead ova are easily recognized from the fact that they become
opaque and white. They are best removed with a glass tube. The thumb is
placed over one end of the tube, and the other end brought directly over
the dead ovum. When the thumb is removed from the end of the tube held
in the hand the water will rush up into the tube, carrying with it the
dead ovum. The thumb is then replaced over the end of the tube, which is
lifted from the water with the ovum retained in it. This tube may also
be used for removing any extraneous bodies which may get into the trays
or boxes.

A form of fungus known as _Byssus_ grows upon dead ova, and it is
principally for this reason that they must be removed. Livingstone Stone
says of _Byssus_:--"With trout eggs in water at 40 deg. or 50 deg. Fahrenheit,
it generally appears within forty-eight hours after the egg turns white,
and often sooner, and the warmer the water the quicker it comes. It is
never quite safe to leave the dead eggs over twenty-four hours in the
hatching boxes. The peculiarity of _Byssus_ is that it stretches out its
long, slender arms, which grow rapidly over everything within its reach.
This makes it peculiarly mischievous, for it will sometimes clasp a
dozen or even twenty eggs in its Briarean grasp before it is discovered,
and any egg that it has seized has received its death warrant." Mr.
Armistead has known it appear within twe