APPENDIX. 



DO GKILSE GKOW TO BE SALMON. 



M. I have frequently heard you remark that a grilse is a 

 distinct fish from a salmon, though of the same family. 



H. Yes ; its instincts in some respects are different, though 

 its habits are precisely the same ; and this is the reason why 

 superficial observers have considered them one and the same 

 fish. 



M. Explain to me how you have arrived at that conclusion, 

 so opposed to the theory generally received ? 



H. The answer to your question can only be developed by 

 degrees, as we proceed with the examination of the subject. 



M. Before proceeding further, I should like to hear your 

 definition of instinct, a word frequently used in connection with 

 animals, but which seems to me to be but little understood ? 



H. Instinct is a law of nature which influences animals with 

 systematic regularity, and without the aid of any reasoning 

 faculty in themselves, to the exercise of those functions bestowed 

 upon them by Providence, in the same mysterious manner as 

 the needle of the mariner's compass is influenced by an invis- 

 ible attraction, always pointing to the north whichever way 

 the compass is placed ; and it would be just as impossible for 

 a salmon to alter its physical shape at will and become a shark, 

 or any other animal, as to deviate from its instinct, as the 



