A CURIOUS THEORY. 23 
either that many of the smolts remain in the sea for 
several years before migrating up-stream as adult salmon, 
or that their rate of growth is either very much more 
irregular, or very much more rapid than is the case in 
Europe. Otherwise, it is impossible to account for the 
large salmon which go up to spawn, and for the small 
salmon which accompany them on the same errand. 
Either the small fish are of the same age as the large, or 
the reproductive age varies, not by a few months, or even 
a year or two, but by several years, in different fish of 
exactly the same species living under exactly the same 
conditions. 
