The Fungus of Salmon Disease. 55 



points that were considered specially necessary to study. 

 Taken as a whole, this evidence is of the most contradictory 

 kind, and shows that fish are attacked by the fungus in large 

 and in small rivers, near the sea and far inland, in pure river 

 water quite unpolluted by sewage or manufacturing bye- 

 products, as well as in rivers where for long distances from the 

 sea every kind of impurity and pollution is common ; and this 

 point in the contrariety of the water question receives full con- 

 firmation from the fact of other similar rivers escaping, and no 

 instance of an outbreak occurring in them. Then, again, 

 although the disease seems to prefer salmon, almost every other 

 kind of fish appear liable to be attacked by it ; and the various 

 kind of trout, more especially the migratory ones, are some- 

 times found dying in numbers, alone or side by side with the 

 salmon ; and as for the salmon themselves, none of them appear 

 to enjoy a perfect immunity; — large and small, fresh run or 

 old fish, all suffer, though in varying numbers, and with 

 marked differences in separate localities. It is observable that, 

 as a rule, it is the large spawning fish that are attacked ; — no 

 instance of epidemics among the freshly-run clean salmon is, I 

 think, noticed in the reports of the inspectors ; but even this 

 occurs in Ireland. The only other point on which any 

 kind of consistency occurs elsewhere is also contradicted here, 

 as, whereas in other localities the disease almost always occurs 

 in winter, or at least during cold weather, it breaks out in Ire- 

 land not only in summer, but also in the clean, freshly-run fish. 

 Winter epidemics of salmon disease are far more disastrous 

 in the injury they cause to a river than outbreaks of the dis- 

 ease on freshly-run fish during the summer. In the former 

 case the fish are not only congregated in far greater numbers, 

 but they are usually killed during their spawning operations ; 

 on the other hand, during an outbreak that requires the 

 stimulus of heat, and attacks fish that are accidentally 

 wounded, owing to their difficulty of freely moving in very low 

 water containing numerous obstacles, the injury is confined to 

 the varying number of fish that are actually killed, as it does 



