Prince. — Why Do Salmon Ascend from the Sea? 135 



Salmonoids are Recent and Plastic. 



Authorities are agreed that the Salmon and its congeners have 

 been evolved in the latest geological times, none of them occurring 

 as fossils, like the Ganoids, excepting in comparatively recent 

 strata. Their plasticity and variable character are no doubt due, 

 as Dr. Gunther held, largely to their recent origin, which contrasts 

 with that of older and more stable fish types. Representatives of 

 the group have been found in the Miocene and Pliocene deposits, 

 and specimens of Osmerus and of Mallotus, enclosed in rounded 

 nodules, are abundant in some Canadian Pleistocene clays and 

 not distinguishable from existing species. The occurrence of 

 land-locked smelt in lakes in the Maritime provinces, and as far 

 inland as the Gatineau lakes, Province of Quebec, 600 or 700 miles 

 from the sea; and especially the land-locked Salmon of Quebec, 

 New Brunswick, and Maine lakes, all point to a marine origin of 

 Salmonoids partially or wholly acclimatized to fresh-water con- 

 ditions. The Chamcook lakes of southern New Brunswick 

 abound with land-locked salmon, and these lakes have been 

 elevated 90 feet by subterranean power, though the distance 

 separating them from the sea-shore is not more than a mile or two. 



Land Elevation Has Defined Salmon Rivers. 



When a submerged area becomes dry land and the ocean 

 recedes, the folds and channels of the sea-bottom become valleys 

 and river channels. The heat of summer and the frigid conditions 

 of winter affect these exposed depressions; and rains, ice, frost, and 

 all the forces of atmospheric denudation, enlarge and deepen 

 them. They become worn into more or less sinuous river-channels 

 draining the surface of the land. Hard strata resist more than 

 soft strata, and water-falls and rapids are formed, but continuity 

 with the ocean is never cut off. What do these changes involve, 

 so far as the movements of fish are concerned? Those sea-fish 

 which deposited their spawn in shallow inshore areas, or in brackish 

 inlets, would find their breeding resorts lifted up, removed as it 

 were far from the sea, and accessible only by a more or less lengthy 

 and sinuous channel. That the channels in the sea are often 

 continuous with the channels of river valleys on land has been 

 clearly established. The best examples, perhaps, are those described 

 by Professor George Davidson, (Proc. Calif. Acad. Sci. 1S9S, 



