invisible during the first few months of their existence,—­these two circumstances combined, have no doubt induced the erroneous belief that the silvery smolts were the actual produce of the very season in which they are first observed in their migratory dress:  that is, that they were only a few weeks old, instead of being upwards of two years.  It is certainly singular, however, that no enquirer of the old school should have ever bethought himself of the mysterious fate of the two-year-old parr, (supposing them not to be young salmon,) none of which, of course, are visible after the smolts have taken their departure to the sea.  If the two fish, it may be asked, are not identical, how does it happen that the one so constantly disappears along with the other?  Yet no one alleges that he has ever seen parr as such, making a journey towards the sea “They cannot do so” says Mr Shaw, “because they have been previously converted into smolts.”

Mr Shaw’s investigations were carried on for a series of years, both on the fry as it existed naturally in the river, and on captive broods produced from ova deposited by adult salmon, and conveyed to ingeniously-constructed experimental ponds, in which the excluded young were afterwards nourished till they threw off the livery of the parr, and underwent their final conversion into smolts.  When this latter change took place, the migratory instinct became so strong that many of them, after searching in vain to escape from their prison—­the little streamlet of the pond being barred by fine wire gratings—­threw themselves by a kind of parabolic somerset upon the bank and perished.  But, previous to this, he had repeatedly observed and recorded the slowly progressive growth to which we have alluded.  The value of the parr, then, and the propriety of a judicious application of our statutory regulations to the preservation of that small, and, as hitherto supposed, insignificant fish, will be obvious without further comment.[16]

[16] Mr Shaw’s researches include some curious physiological and other details, for an exposition of which our pages are not appropriate.  But we shall here give the titles of his former papers.  “An account of some Experiments and Observations on the Parr, and on the Ova of the Salmon, proving the Parr to be the Young of the Salmon.”—­Edinburgh New Phil.  Journ. vol. xxi. p. 99.  “Experiments on the Development and Growth of the Fry of the Salmon, from the Exclusion of the Ovum to the Age of Six Months.”—­Ibid. vol. xxiv. p. 165.  “Account of Experimental Observations on the Development and Growth of Salmon Fry, from the Exclusion of the Ova to the Age of Two Years.”—­Transactions of the Royal Society of Edinburgh, vol. xiv. part ii. (1840.) The reader will find an abstract of these discoveries in the No. of this Magazine for April 1840.

Having now exhibited the progress of the salmon fry from the ovum to the smolt, our next step shall be