NATURAL HISTORY OF THE SALMON. 81 



got upon slippery ground, tries to slide off with the re- 

 mark that " this distinction is observable in the smolts 

 also." This is quite a new statement, never heard of 

 before, and therefore the more imperatively requiring 

 that proof of which it has as yet received none. Who has 

 observed the distinction ? — where is it recorded ? Every 

 schoolboy on the banks of the Tweed (where almost 

 alone the solar and the eriox are found together in 

 plenty) knows at a glance the difference between the 

 smolt of the salmon and of the bull-trout — the "black- 

 fin" and the " orange-fin." But the knowledge of the 

 alleged distinction between the smolt of the salmon and 

 of the grilse, if not hitherto confined to Mr. Mackenzie', 

 is a piece of useful knowledge certainly not yet diffused. 

 Mr. Mackenzie tries again : " The absurdity of the 

 theory consists in the assertion that the smolts of salmon, 

 going down to the sea in company with the smolts of 

 grilse, also return from the sea under the denomination 

 of grilse." "Where is the absurdity ? There is just as 

 much absurdity in supposing that the families of ewes 

 who ha,ve never bred before, and of ewes who have 

 often bred before, both appear under the denomination 

 of lambs. 



A pretty strong point made by Mr. Mackenzie is the 

 allegation, supported by many appearances, but also 

 contradicted by some facts, that salmon and grilse are 

 never seen paired in connubial relations. This would be 

 a powerful fact if established, for we do not see the 

 young of any other species cohabiting only with the 

 young, or the old only with the old. But then, in the 

 case of animals in their wild or natural state, we have 



