21 MR. MORTON ALLPORT ON THE [Jan. 13, 
The proportion of living ova deposited was estimated at above 
45 per cent. of all sent out. Since the deposition of the ova in 
April, 1864, several great improvements had been effected by the 
Commissioners in the arrangements at the Plenty, the chief of which 
was the alteration of the gravel in the breeding-boxes. ‘To explain 
the change and the advantages of the present plan, it must be re- 
membered that 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 three or four 
pounds, the spaces between which are of course large enough to per- 
mit the ova to roll down to depths varying from a few inches to a 
foot and a half. This is no doubt a wise provision of nature for the 
protection of the ova and the helpless young fry from their innume- 
rable 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 trans- 
ferred 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 decomposing, to say nothing of the ill effects which the decay- 
ing ova would have upon the water generally. Again, it is now an 
ascertained fact that a considerable admixture of atmospheric air is 
indispensable in hatching the ova of most of the Salmonide, and 
that, consequently, the further 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 3 or 4 
inches down into the 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 in favour of keeping the 
ova in sight, that the Commissioners replaced the coarse gravel for- 
merly used by an even bed of very fine pebbles on which the ova 
rested about an inch from the surface of the stream, which was made 
to flow gently and evenly through the boxes. The result was, that 
the moment an egg became opaque, or, in other words, died, it was 
removed, and all danger to the neighbouring ova was avoided. Be- 
sides this alteration, a long series of gravelly rapids, with a few deep 
places interspersed, was added to the lower end of the Salmon-pond, 
and a new circular pond with a gravelly rill attached was constructed 
for the Salmon-trout. 
On the 8th of May, 1866, the first Salmon-ovum per ‘ Lincoln- 
shire ’ hatched, and on the 12th of the same month the first Sea-trout 
ovum. By the time all were hatched the Superintendent reported 
that he had counted up to 4490 Salmon-fry and 496 Sea-trout fry, 
