58 FISH HATCHING. 



the stone-fly, and it immediately occurred to 

 me that I was destroying a most efl&cient 

 assistant, and that the water-ouzel was one 

 amongst the many exquisite links constantly 

 presenting themselves to the student of the 

 natural history of this valuable fish. During 

 the formation of the spawning-bed, the 

 salmon turns over gravel, in the interstices 

 of which lie the larvae of aquatic flies, to 

 which the water-ouzel is debarred access 

 until so turned over by the salmon ; and the 

 more frequent the visits of this useful bird to 

 the newly-turned gravel, the freer will the 

 spawning-bed be from these hurtfiil insects. 

 This opinion subsequent experience has con- 

 firmed, and preservers of salmon will act 

 wisely to protect, as a most able assistant, the 

 falsely-accused water ouzel. — J. H. Hobsfall." 



