The Fungus of Salmon Disease. J i 



where they are favoured by quiet water. Where, however, 

 suitable food is to be found in a river, and our fungus can fix 

 its roots, it would be an extremely difficult, if not impossible, 

 task to exterminate it without the use of an antiseptic, which 

 would be injurious to the fish also ; for its very quick and plen- 

 teous reproduction, the diplanetic provision of movement pos- 

 sessed by the spores, and their long periods of torpidity to resist 

 starvation on unfavourable surroundings, render the fungus ex- 

 tremely resisting. When endeavouring to account for these peri- 

 odic outbreaks of salmon disease, it is necessary to consider the 

 conditions of favourable life in the fish as well as the fungus, and 

 to do this in the broadest sense. The problem is a most difficult 

 one, as the practical evidence seems to be contradictory at almost 

 every point; but there area few elementary facts that at the outset 

 are forced upon us. The distribution of the spores of the fungus 

 of salmon disease is so general that it would be unsafe to assume 

 that the outbreak was due to their sudden arrival and intro- 

 duction into our rivers. On the contrary, we have every reason 

 to believe that the disease in isolated cases has never been 

 absent from our rivers — indeed, such instances are now of 

 frequent occurrence in rivers where the epidemic form of the 

 same disease is unknown. The periodic manner in which the 

 disease breaks out, and again disappears to occur surely the 

 following year, clearly proves that fish can live happily in in- 

 fected rivers — that is, in waters where the spores of the fungus 

 pre-exist, and possess the same readiness to germinate as before. 

 If this was not the case, epidemics would be more frequent, 

 and theoretically, at least, not a fish could escape. The manner 

 in which fish can live side by side with the fungus is also illus- 

 trated by the way in which trout can thrive in water that must 

 be swarming with the seeds of the disease as liberated from 

 diseased salmon at the time of epidemics, and yet not be quite 

 invulnerable, as occasional trout have been known to die of 

 salmon disease during these periods. During the warm weather 

 of last summer I was present when a net was drawn, and nearly 

 a hundred salmon taken from a river ; — the net was used, as 



