corresponding size, owing to the entire absence of marine
agency.

[25] Another interesting result may be noticed in connexion
with this Compensation Pond. The original streamlet, like most
others, was naturally stocked with small "burn-trout," which
never exceeded a few ounces in weight, as their ultimate term
of growth. But, in consequence of the formation above referred
to, and the great increase of their productive feeding-ground,
and tranquil places for repose and play, these tiny creatures
have, in some instances, attained to an enormous size. We
lately examined one which weighed six pounds. It was not a
sea-trout, but a common fresh-water one--_Salmo fario_. This
strongly exemplifies the conformable nature of fishes; that is,
their power of adaptation to a change of external
circumstances. It is as if a small Shetland pony, by being
turned into a clover field, could be expanded into the gigantic
dimensions of a brewer's horse.

Having narrated the result of Mr Shaw's experiment up to the migratory
state of his brood, we shall now refer to the further progress of the
species. This, of course, we can only do by turning our attention to the
corresponding condition of the fry in their natural places in the river.
So far back as the 9th of May 1836, our observer noticed salmon fry
descending seawards, and he took occasion to capture a considerable
number by admitting them into the salmon cruive. On examination, he
found about one-fifth of each shoal to be what he considered sea-trout.
Wisely regarding this as a favourable opportunity of ascertaining to
what extent they would afterwards "suffer a sea change," he marked all
the smolts of that species (about ninety in number) by cutting off the
whole of the adipose fin, and three-quarters of the dorsal. At a
distance, by the course of the river, of twenty-five miles from the sea,
he was not sanguine of recapturing many of these individuals, and in
this expectation he was not agreeably surprised by any better success
than he expected. However, on the 16th of July, exactly eighty days
afterwards, he recaptured as a _herling_ (the next progressive stage) an
individual bearing the marks he had inflicted on the young sea-trout in
the previous May. It measured twelve inches in length, and weighed ten
ounces. As the average weight of the migrating fry is about three and a
half ounces, it had thus gained an increa