78 THE SALMON. 



alone the migratory Salmonidce, subsequent to the infant 

 stages, have any perceptible growth. A different result 

 is seen in the case of trouts, the average weights of 

 which decrease during those summer months during 

 which the young, or first-ascenders of the species, add 

 themselves to the older fish ; a comparison between the 

 two columns in respect of weight, as we have already 

 seen in respect of number, showing just such differences 

 as would arise from one column comprising only old fish, 

 and the other both old and young. 



But, besides showing that Mr. Mackenzie fails to 

 make anything in his favour out of the facts as to 

 weight and size, we show that, in at least two respects, 

 those facts are dead against him. 1st, There is a great 

 range between largest and smallest in salmon, and a very 

 small range in grilse ; 2d, There are very few roundly 

 speaking almost no salmon of those weights which may 

 be called the grilse weights. Taking even monthly aver- 

 ages, which obviously can bring out veiy imperfectly the 

 facts we speak of, the average weight of Tweed salmon 

 in one month is 7 Ib. lOf oz., and in another month 

 16 Ib. 2 f oz. ; and everybody knows that there are com- 

 paratively few salmon below the smaller of those monthly 

 averages, and a great many above the larger a fact 

 corroborated by the month which shows the largest 

 average weight showing the greatest average number, 

 and by the month which shows the lowest average 

 weight showing also by far the smallest number. But 

 we do not see this in grilse the difference between the 

 smallest and the largest (excluding, of course, rare in- 

 dividual cases), being seldom so much as three pounds. 



