146 THE HABITS OF THE SALMON. 



authenticated instance of a bull-trout, which was 

 marked in the Tweed, having been caus^ht by the 

 nets on the coast of Norfolk, and for aught we know 

 salmon may travel as far away from their native 

 rivers as mid-ocean. I can affirm of my own know- 

 ledge, that there are a certain number of diseased 

 fish in the sea, and as there is 2. prima facie evidence 

 that diseased fish belonging to one river can commu- 

 nicate the disease to fish belonging to other rivers, 

 it is just possible that some of the diseased Sol way 

 Firth fish came across some Tweed fish during their 

 rambles in the sea, which might thus account for the 

 sudden outbreak of saprolegnia in the Tweed ; but 

 the most probable theory to account for its appear- 

 ance in the Tweed, as well as in other rivers, is that 

 the seeds of saprolegnia lie dormant in the bed of 

 the river which, under certain unknown conditions, 

 germinate and produce a fungus, from which spores 

 get detached, one of which, according to Professor 

 Huxley, is sufficient to kill any salmon it comes in 

 contact with, provided it adheres and germinates, 



