FOOD OF FISH AND ITS PRODUCTION. 91 



part. Nothing living comes amiss, but doubtless 

 some kinds of food agree with them far better than 

 others. But we know very little on this branch of 

 the subject. It is dreamland to us, with a very little 

 ascertained waking reality. What do we know even 

 of the various breeds of the same species of fish, 

 save the bare fact of their existence ? What do we 

 know of the food and conditions most favourable 

 to them ? Consider the trout. Can any fish display 

 greater diversity or variety of size and value than 

 trout ? And how do we account for it ? 



Trout in one stream will be much larger, firmer, 

 redder, and better shaped than in others. This may, 

 in a measure, be owing to the greater abundance of 

 food ; but I have every reason to believe that it pro- 

 ceeds quite as much from the kind of food that they 

 are enabled to obtain. In some rivers and lakes we 

 find the trout large, handsome, red, and vigorous fish ; 

 in others, we find them small and meagre ; nay, even 

 in the same lake the fish will be influenced in a 

 strange way by locality, so much so that the very 

 breed even appears to be different. It would seem 

 difficult to account for this peculiarity upon any 

 other hypothesis than that of food and the nature 

 of the water and soil around them, and yet the 

 fish appear to be a totally different breed; and it 



