22 JANUARY 



whether the old one fed the three young in turn, or 

 whether it was first come first served. 



VIII 



Not less mysterious than the migratory impulse 

 spring among birds is that which regulates the 



Salmon seasonal movement of salmon. That 

 they should ascend rivers in the autumn floods is 

 intelligible enough, seeing that they spawn in 

 November and December. In like manner, as birds 

 fly as near home as they can to nest, so the instinct 

 of salmon takes them back to their native shallows 

 to reproduce their kind. These inland waters are 

 the home not only of the individuals, but of the 

 race; for it is probable that salmon and brook 

 trout were originally one and the same species. 

 Adventurous individuals of the trout kind dropped 

 into the estuaries of post-pliocene streams in search 

 of food, just as they may be observed to do at 

 this day, whence the boldest and strongest of them 

 pushed on into the ocean, where food of the richest 

 kind is most abundant. They got over the prelimi- 

 nary qualms of sea-sickness, throve abundantly, 

 their complexion changed, they acquired all the 

 airs of pelagic fish, and despised the timid lands- 



