SAPROLEGNIA PER AX, SALMON DISEASE. 157 



warmer ? This, of Itself, may be the immediate 

 cause of the reappearance of disease in rivers in 

 which it is supposed to have died out. Salmon roam 

 about in the sea in shoals, and should one of a shoal 

 happen to be diseased, it would not be surprising if 

 the whole shoal eventually exhibited disease after 

 their arrival in fresh water. I am at a loss to 

 account in any other way for the fact that so few 

 early ascending fish are affected with saprolegnia. 

 It would be interesting if a record were kept to show 

 whether or not the spring had been a mild one in 

 those years when signs of disease appeared amongst 

 the early fish. 



My remarks have been so far confined to sapro- 

 legnia among salmon, but it should not be forgotten 

 that non-migratory fish, affected with the same 

 disease, remain behind in the rivers after all the 

 surviving diseased salmon have gone to sea. These 

 fish have no access to a salt-water bath, and the 

 question arises as to what becomes of them. Many 

 must die as well as salmon, but we do not hear oi 



