124 FISH O0LTUKE. 



trout, as well as other fish, depend almost wholly 

 upon the supply of food, and I think I have shown 

 that the particular kinds of food are also a great 

 desideratum. Now, it being known that particular 

 kinds of weed are favourable to the production of 

 certain species of insects, what can be easier — when 

 the soil is favourable to such a measure — than to 

 transplant a sufficient quantity of these weeds, and 

 the larvEe of the insects which will almost always 

 be found to abound in them, from one lake and from 

 one stream to another ? For example, with respect to 

 the gammari so often noted, what could be easier 

 than to transplant weed ? This would serve as food 

 for the large fresh-water mussel found in almost all 

 waters, and it would serve as food for the gammari, 

 which in turn would serve as food for the fishes. It 

 may be said, with regard to some lakes and streams, 

 that they are so gravelly and rocky, that the weeds 

 would hardly thrive in them ; but it is seldom indeed 

 that some nooks and corners do not exist, in or about 

 the banks of lakes and streams, where there may be 

 found sufficient soil, which, with a slight admixture 

 of the natural soil, and a judicious planting of these 

 weeds, may not be made to grow them to some small 

 extent; and the weeds, once introduced, wUl gradually 

 increase year by year, forming their own soil, and 



