SAPROLEGNIA FERAX, SALMON DISEASE. 145 



mouthshire. I cannot fix the date on which it first 

 made its appearance in the Usk, but as this river is 

 not mentioned in the report of 188 1, it must 

 presumably have been after the date of the report. 



As saprolegnia is an infectious or contagious 

 disease, it is not surprising that it spread in the first 

 instance to rivers in the Solway Firth, adjoining the 

 "Esk and the Nith, but it is difficult to account for 

 its appearance in Scotch rivers on the east coast, and 

 also in the Welsh rivers, and not in rivers intervening. 

 The Ribble in Lancashire, adjoining the Lune ; the 

 Dovey, the Towey, and Teifi on the Welsh coast, 

 and all the rivers from the Doon in Ayrshire round 

 the north coast of Scotland, as far as the North Esk, 

 are all intervening rivers which appear to have 

 been free from disease, but the most unaccountable 

 incident is, that meanwhile^ the Tweed was the first 

 river in which it made its appearance after the out- 

 break in the Nith and the Esk in the Solway Firth. 

 No one is able to say where migratory fish go to 

 during their sojourn in the sea ; there is a well- 



