398 Proceedings of the Royal Society of Edinburgh. 



eggi which is of course attached to them by the umbilical vessels, 

 or more properly, by the ompholo-mesenteric vessels. During 

 this period, they do not eat or grow much, but without doubt 

 acquire strength. When the yoke on which they have been feed- 

 ing becomes nearly exhausted, they rise from their sandy and 

 gravelly bed, making their way to the surface, through a thickness 

 varying from one to two feet, and at last gain their new habitat in 

 the waters. In ten days they may be caught in the rivers, very 

 considerably grown, and in twenty days have attained a length 

 varying from eight to nine inches. • 



An extensive personal inquiry shewed that they are never the 

 prey of trout ; and a more limited one renders it doubtful if they 

 ever become the prey of kelt, or spawned salmon, on its return to 

 the ocean. It is probably to avoid the effects of severe frosts, that 

 the salmon selects the bed of the running stream as the spot for 

 the favourable deposition of the ova. The beds of rivers, he con- 

 jectures, must vary somewhat in temperature ; and the author 

 supposes, that extreme frosts are less likely to reach the gravel 

 under the stream than under the pool. Frequent experiment has 

 convinced the author, that the opinions of Sir Humphry Davy, 

 Jacobs and others, — opinions which maintain that the gravel 

 below the stream is selected by the salmon, on the ground of the 

 better aeration of the ova, have no real foundation whatever. 



The food of the fry has been determined precisely, and their 

 whole habits, by repeated anatomical examinations made by him- 

 self. 



The salmon seems to hybernate somewhat in certain seasons ; a 

 great number of salmon and trout do not enter into the spawning 

 condition, and consequently may be got in first rate order as food, 

 at any time, provided they have the means of subsistence : now, 

 this the salmon can always get at in the ocean, which is his true 

 feeding ground. He cannot get food in rivers of the kind he de- 

 sires. The salmon-trout, on the contrary, even at the mouths of 

 rivers, will take to the fry of other fishes, to small fishes, and 

 to worms ; and in rivers, he will feed on the larvae of insects, in- 

 sects themselves, and, in short, on the ordinary food of trout. 



The true salmon prefers a peculiar kind of food, the ova of the 

 echino-dermata, and takes, with great reluctance, any other. 

 Hence, the moment he enters rivers, having abandoned his 

 natural feeding ground, he deteriorates constantly, refuses all 

 kind of food, loses weight and flavour, and gets, in short, entirely 



