AGE OF EMBRYO AT DATE OF PACKING OVA. 45 



importance that the water be fully described to the pisciculturist 

 from whom the stock is obtained. 



AGE OF EMBRYO AT DATE OF PACKING OVA. 



The percentage of incubation which the embryo has accom- 

 plished is of more importance in the success of the consignment 

 than has hitherto been supposed. 



As far better results can be obtained in large hatching-houses 

 properly furnished with all the best appliances than in the 

 hatching-trays at the command of most amateurs, as a general 

 rule it is desirable to pack the eggs after 90 per cent, of the 

 period of incubation has been accomplished ; and where the ova is 

 to be laid down in redds, we usually pack it when only 2 per 

 cent, of the period of incubation remains, so that it would hatch 

 out within a few hours of being laid down in the redd, thus 

 avoiding all danger from sediment, which in some water would 

 suffocate the ova in less than ten days. Muddy water seems to 

 have no terrors for alevins, who, by herding together, keep portions 

 of the redd clean, and, like other children, revel in a little dirt. If 

 the journey is long, and the weather warm, a little snow or 

 powdered ice mixed with moss placed in the air-tray obviates 

 any danger of the eggs bursting before they are unpacked. 

 Neither ice nor snow must be used withoxit being well mixed with 

 dry moss, powdered charcoal, or old white-wood sawdust, as, if 

 the temperature rose in the box after the moss pads become 

 saturated with melted water, embryos on the point of hatching 

 would run much risk of suffocation. So long as the ice remains, 

 the temperature in the trays is sufficiently low to check the 

 exudation of carbonic acid from the ova, and the oxygen in the 

 moss pads is amply sufficient for the requirements of the embryos. 

 When eggs are packed ten days before they are due to hatch, 

 there is little danger of suffocation, even if the moss become 

 saturated. But the great secret of the successful transportation 

 of ova is to keep the moss only damp not wet, unless a low 

 temperature can be ensured during the whole time of transporta- 

 tion. In packing ova to send to the antipodes, they need not be 



