The most remarkable phase in the life of the salmon is its extraordinary instinct for change. After the parr has become a smolt, it is found that the desire to visit the sea is so intense, especially in pond-bred fish, as to cause them to leap from their place of confinement, in the hope of attaining at once their salt-water goal; and of course the instinct of river-bred fish is equally strong on this point—they all rush to the sea at their proper season. There are various opinions as to the cause of the migratory instinct in the salmon. Some people say it finds in the sea those rich feeding-grounds which enable it to add so rapidly to its weight. It is quite certain that the fish attains its primest condition while it is in the salt water; those caught in the estuaries by means of stake or bag nets being richer in quality, and esteemed far before the river fish. The moment the salmon enters the fresh water it begins to decrease in weight and fall from its high condition. It is a curious fact, and a wise provision of nature, that the eel, which is also a migratory fish, descends to spawn in the sea as the salmon is ascending to the river-head for the same purpose; were the fact different, and both fish to spawn in the river, the roe of the salmon would be completely eaten up. In due time then, we find the silver-coated host leaving the rippling cradle of its birth, and adventuring on the more powerful stream, by which it is borne to the sea-fed estuary, or the briny ocean itself. And this picturesque tour is repeated year after year, being apparently the grand essential of salmon life. [Illustration: SMOLT TWO YEARS OLD. Half the natural size.]