448 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



question Trbetlier a salmon wliicli enters water in which Saprolegnia is 

 present shall be infected or not depends upon the mutual adjustment of 

 a vast variety of conflicting agencies. Until we have learned something 

 more than we at present know of these agencies, and of the history of 

 the salmon Saprolegnia itself, there can be no thoroughly safe founda- 

 tion for any view which may be j)ut forward as to the best mode of 

 dealing with the disease. 



Nevertheless, since it is evident that every diseased salmon which re- 

 mains in a river must immensely increase the chances of infection of the 

 healthy fish in that river, the policy of extiri^ating every diseased fish 

 appears, theoretically, to be fully justified. But whether, in endeavor- 

 to carry such a policy into effect in any given river, the cost would not 

 exceed the loss from the disease, is a point which must be left for the 

 consideration of boards of conservators. 



We have the honor to be, sir, your obedient servants, 



S. WALPOLE, 

 T. H. HUXLEY, 



Inspector's of Fisheries. 

 The Eight Hon. the Seceetary of State 



FOR THE Home Department. I 



I 



