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XXIII. On the Growth of Grilse and Salmon. By Mr ANDREW YOUNG, Inver- 

 shin, Sutherlandshire. In a Letter addressed to JAMES WILSON, Esq.,' F.R.S.E. 

 Communicated by Mr WILSON. 



(Bead 9th January 1843.) 



THE history of the habits and development of the salmon has been for ages a 

 subject of dispute, even among men of science and experience. The general theory 

 which prevailed regarding its earlier stage of existence was, that the spawn depo- 

 sited in the autumn or beginning of winter, produced by development the smolts 

 which were seen descending to the sea in the course of the next ensuing spring. 



In regard to its after state, some supposed that the smolts which descended 

 the rivers in spring or early summer returned as grilses that same season. Manj r 

 doubted this theory, and maintained that it was impossible, or very improbable, 

 that they should return so speedily in that greatly enlarged condition ; their only 

 argument, however, being founded on the unlikelihood of such a rapid growth. 



Others, again, have maintained the opinion that the grilse is a distinct species 

 of fish, closely allied to, but not identical with, the true salmon, and that in the 

 so-called condition of grilse it has attained to its ultimate state. In fact, this has 

 been asserted not only by naturalists, viewing the subject somewhat vaguely as 

 one with which they had no great acquaintance, but also by practical, that is, 

 professional fishermen, whose opinions, from their more enlarged experience, were 

 supposed to carry greater weight. But till recently all these various opinions were 

 uncertain and unsatisfactory, in so far as they were founded upon supposition, 

 without proof or trustworthy experiment. 



But in regard to the first, or, as I may call it, fresh-water state of the fry of 

 salmon, Mr JOHN SHAW of Drumlanrig, several years ago commenced, and some 

 time ago concluded, a series of most sagacious and well known practical expe- 

 riments, which settled that part of the subject. I lately visited Mr SHAW'S expe- 

 rimental ponds, and carefully examined his various specimens, from the ova to 

 the smolts, and I am perfectly convinced of the accuracy of the results, and of the 

 correctness of the general conclusions which he has drawn. This I believe would 

 have been my opinion, judging simply from Mr SHAW'S explanations ; but I am 

 happy to say (and think it my duty so to do), that my own more recent experi- 

 ments, undertaken upon similar principles, though not for such a length of time, 

 have led to the same results. I have as yet gone no further than to a period cor- 

 responding to Mr SHAW'S first season ; but this decidedly confirms Mr SHAW'S 

 principal discovery, by confuting the idea entertained by our ancestors, that the 

 fry became smolts during the first spring after the ova were spawned. All my 

 confined specimens are still in the state of parr, exactly as described by Mr SHAW, 

 with this difference, that their dimensions are somewhat greater ; and I therefore 



VOL. XV. PART III. 4 Z 



