456 SALMON AND TROUT. 
panies have been most obliging in allowing certain other privi- 
leges which have gone far to insure st.ccessful transport, and 
from that time the ova which I have received from America, as 
well as those which I have exported, have arrived in excellent 
condition, 
There are three causes of failure in exporting ova, viz. 
imperfect fecundation, bad packing, and heating on the voyage. 
The distribution of ova within the limits of Great Britain 
and Ireland, or indeed all over Europe, is a very simple matter, 
and is done on a large scale by leading pisciculturists. For a 
journey of several days it is sometimes necessary to place some 
rough ice in the package to keep the temperature down. If 
they are to be many days on the journey, they should be sent 
off as soon as the outline of the fish and the eyes are distinctly 
visible ; this leaves a margin of fifteen to twenty days, according 
to the temperature of the water into which they are afterwards 
placed, before the hatching period arrives. 
When the eggs are all ‘eyed,’ the pisciculturist has but to 
remove any sediment settling on the ova, and to pick out 
occasionally a dead one. In the best water available for hatch- 
ing purposes, there is always a s/ight sediment after it has run 
through the troughs five or six weeks, but this can be got rid of 
by removing the ova from the troughs, and washing them— 
in the tray system, by lifting the trays up an inch or two, say 
half-a-dozen times, and replacing them, or in the glass grille 
system, by sprinkling clean water over the eggs from a watering- 
pot. A hatching-house should be fitted with a ‘sink’ five or 
six feet long, where any washing can be done. 
Nature will now do the rest of the work in good time, and 
with very little help on our part. The greatest assistance we offer 
nature is in the protection of the ova and newly-hatched fish 
from every natural enemy during the most helpless part of 
its existence ; the only part of fish-hatching which is purely 
artificial is the taking of the eggs from the parent fish. 
As soon as the great ‘hatch’ comes on, there is more work 
for the pisciculturist in removing the empty egg-shells from the 
