448 SALMON AND TROUT. 



panics have been most obliging in allowing certain other privi- 

 leges which have gone far to insure successful 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 slight 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 



