68 THE SALMON. 



spring, l)ut an all-tlie-year fish, the other niamly a 

 summer fish. All that we maintain, on the evidence yet 

 adduced, is that the facts are at least equally compatible 

 with, and indeed entirely suitable to, the theory, that the 

 fish coming up all the year are the adults of various ages, 

 and that those rushing up in a body in summer are the 

 young of the same species. 



To the same effect, though necessarily with less dis- 

 tinctness, is the rather curious evidence supplied by the 

 trout column in the preceding table, which, according to 

 the hypothesis we are maintaining, differs from the salmon 

 column, comprising only adults, and from the grilse 

 column, comprising only what we shall call, perhaps not 

 with strict accuracy, adolescents, in comprising both the 

 adults and the adolescents of another species. Because 

 the trout column comprises adults, it shows, like the 

 salmon column, a larger or smaller number ascending 

 every month in the year ; because it contains also 

 adolescents, it shows, like the grilse, a great and sudden 

 increase in certain summer months. Up till the end of 

 May, the trouts are few, but in June they suddenly increase 

 by 3 per cent., salmon in that month increasing only 1 2 

 per cent., and they increase another 50 per cent, in July, 

 in which month nearly a fourth of the whole capture 

 is obtained. We account for this feature by saying that 

 here we see the effects of the adolescent trouts, on their 

 first ascent, being added to the adults ; and, though 

 rather anticipating another portion of our argument, we 

 may add, that this view is supported by the falling ofl' 

 in the average weight of trouts during the months when 

 we sup})ose the young to l)e makino- their first ascent. 



