n8 THE EVOLUTIONIST AT LARGE. 



salmon himself is only a river trout who has 

 acquired the habit of going down to the sea, 

 where he gets immensely increased quantities 

 of food (for all the trout kind are almost om- 

 nivorous), and grows big in proportion. But 

 he still retains many marks of his early exist- 

 ence as a river fish. In the first place, every 

 salmon is hatched from the egg in fresh water, 

 and grows up a mere trout. The young parr, 

 as the salmon is called in this stage of its 

 growth, is actually (as far as physiology goes) 

 a mature fish, and is capable of producing 

 milt, or male spawn, which long caused it to 

 be looked upon as a separate species. It 

 really represents, however, the early form of 

 the salmon, before he took to his annual ex- 

 cursion to the sea. The ancestral fish, only 

 a hundredth fraction in weight of his huge 

 descendant, must have somehow acquired the 

 habit of going seaward possibly from a dry- 

 ing up of his native stream in seasons of 

 drought. In the sea, he found himself sud- 

 denly supplied with an unwonted store of 



