MARINE VERTEBRATES 321 



Of these we will take first the family Salmonidez, of which the 

 Salmon (Salmo salar), and the Smelt (Osmerus eperlanus) are 

 well-known examples. Several species of the family are remark- 

 able for their periodical migrations from fresh to salt water 

 or vice versa, and we cannot do better than briefly relate the 

 interesting life-history of the salmon as a striking instance of these 

 peculiar wanderings. This fish quits the sea at the close of the 

 summer, and ascends the rivers for the purpose of depositing its 

 spawn, the colder water of the rivers being necessary for the 

 development of the young. Its upward journey is beset with many 

 difficulties, for it has to shoot the various rapids and leap the 

 cascades, the latter often demanding the most prodigious efforts on 

 the part of the fish, which frequently leaps several feet out of the 

 water, and even then has sometimes to renew its attempts over and 

 over again before it finally succeeds. Indeed, the difficulties to be 

 overcome are so numerous that the fish often reaches the goal in 

 such an exhausted condition that it would hardly be recognised as 

 the salmon by those who have only seen it in the prime condition 

 in which it is captured during its return to the sea in the following 

 spring or summer. The male, at this period called the kipper, is 

 of a dull red colour, irregularly blotched with yellow and light 

 brown, and its skin is covered with a slimy secretion. Its body is 

 lean, and the head, now large and out of all proportion, is rendered 

 still more unsightly by the protrusion of the lower jaw, which at 

 this season, when the males are particularly pugnacious, becomes a 

 formidable weapon of offence. The condition of the female, now 

 called the baggit, is equally poor, and the skin has changed its 

 bright silvery colour for dark and dingy shades. 



The female digs a nest in the form of a deep trench by 

 wriggling her body in the gravel of the bed of the stream, and there 

 deposits her eggs, many thousands in number, small quantities 

 at a time. As each batch is deposited the eggs are fecundated 

 by the kipper, and then covered over lightly with gravel by the 

 baggit ; and this work having been accomplished, both male and 

 female rest and feed, with the result that their condition is rapidly 

 improved. 



After about eighteen weeks the eggs begin to hatch, and the 

 fry wriggle out of the nest and seek shelter under stones in the 

 immediate neighbourhood. They are now peculiar little creatures, 

 as much like tadpoles as fishes, with big heads and narrow bodies, 

 and a bag of albuminous yolk-matter attached to the ventral side. 



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