46 



the sea-trout, tho pupils of the eyes in which hist sUind out as 

 ]>hick spots on a yellowish white ground, the enveloping 

 tissue being evidently more transparent than in salmon ova. 



Many are so far advanced that I fully expect to hear of 

 their hatching within a week. I estimate the proportion of 

 living ova now deposited at above 45 per cent, of all sent out. 

 Since the deposition of the ova in April, 1864, several great 

 improvements have been effected by the Commissioners in the 

 arrangements at the Plenty, the chief of which has been the 

 alteration of the gravel in the breeding boxes. To explain 

 the change and the advantages of the present plan, I must 

 ciill your attention for a few moments to the habits of the 

 salmon in a state of nature. In its own rivers the salmon 

 chooses for its spawning beds shallow^ rapids running over a, 

 bottom of coarse river gravel, consisting of pebbles weighing 

 from half a pound to 3 or 4 lbs., the spaces between which 

 are of course large enough to permit the ova to roll down to 

 depths varying from a few inches to a foot and a half. This 

 is no doubt a w- ise provision of nature for the protection of the 

 ova and the helpless young fry from their innumei-uble natural 

 enemies, but has serious objections in artificial rearing. To 

 begin with, it is absolutely impossible in the first instance to 

 separate the dead from the living ova : all must be rapidly 

 transferred to the water together, and the dead ova gradually 

 picked out afterwards. In 1864 numbers of dead and living 

 ova together got out of sight between the interstices of the 

 gravel, purposely made to resemble as nearly as possible the 

 natural spawning beds, and much of the living ova was 

 assuredly destroyed by contact with that which was decom- 

 posing, to say nothing of the ill effects which the decaying ova 

 would have upon the w^ater generally. Again, it is now 

 an ascertained fact that a considerable admixture of atmos- 

 pheric air is indispensable in hatching the ova of most of the 

 Salmonidte, and that, consequently, the farther the ova are 

 from the surface of the water the more tumble and splash you 

 must have in the water to drive bubbles of air through and 

 amongst the gravel. It follows that if in artificial rearing the 

 ova are allowed to get some three or four inches down into 

 gravel, a sharp stream of water must be directed over the 

 artificial beds to supply them with the air necessary, but that 

 if it is desired to keep the ova in sight they must be placed on 

 fine gravel, and an even gentle stream of water about an inch 

 or an inch and a half in depth must flow through the beds. 

 As in the artificial process the boxes are thoroughly guarded 

 from all possible enemies, the advantages are so manifestly 

 i.1 favor of keeping the ova in sight that the Commissioners 

 have replaced the coarse gravel, formerly used, by an even bed 



