On the growth of the salmon, from the egg to the adult / by R. Knox.

  • Knox, Robert, 1791-1862.
Date:
[1855]
Catalogue details

Licence: Public Domain Mark

Credit: On the growth of the salmon, from the egg to the adult / by R. Knox. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    a few common Irout: on every hypothesis, save one, the absence of the parr in these and the adjoining streams is inexplicable: the fishing took place in May; the sea trout and smolls were descending to the sea: the net took everything to the minnow, yet no parrs were to be found: on one hypothesis alone is this explicable, namely, that the young of the sea trout, hatched from the ova deposited in November of the preceding year, had all become smolts, and were proceeding to the sea. If the age of these smolts had been two years or even one year, the young fish, in their generic or parr dress, must have been found in the streams and pools : nothing of the sort occurred: had the smolts, then and there found, being the females of one year, the males of the same age, but less in size, not as yet changed into smolts, must have been discovered in the net: in a fishing of some miles nothing of the kind appeared. 3. That these fish, called parr, are male and female; that in the female the roe remains always at its minimum; in the male, on the contrary, the milt enlarges remarkably during the autumn and winter months, and not infrequently is found enlarged at all times of the year. 4. That, in addition to river trout of various sizes, and of parr, which never exceed eight or nine inches in length, there appear suddenly as it were, in the streams, in May, thousands of a small fish (the smolt) covered with silvery scales, which fish is presumed to be, and has been pi'oved to be, the young of the salmon and sea trout. It was first remarked by Mr. Hutchinson, of Carlisle, in 1782, and subsequently by all who observed what happened to the smolt when kept for some time and roughly handled, that the scales being rubbed off, the smolt assumes the appearance of a parr; but Mr. Hutchinson did not think that this proved the smolt and parr identical. What is the age of these fish—of the May smolts ? The whole question of the protection of the salmon is wrapped up in this question. The question of its identity with the parr is a distinct question ; the presence,of the parr-markings to be discovered under the scales pi'oves nothing specifically, since these are generic characters common to the whole natural family of the Salmonidae at a certain period of their growth or development to trout and salmon of every kind. 5. It was asserted by Willoughby (1686), and the assertion has not been refuted, that with the developed milt of a male parr, 6 or 7 inches in length, the ova of a full-grown salmon may be fecundated. If we adopt the theory, that under every circumstance the parr is simply a young salmon or salmon trout, as the case may be^ the astounding physiological fact first announced by Willoughby still