78 The Fungus of Salmon Disease. 



differ, the case is quite different with salmon, as they are said 

 to feed only in the sea, where the chance of supplies ought to 

 be pretty constant ; and salt water fish do not present the vary- 

 ing appearance of salmon, which, from two neighbouring rivers, 

 and probably the very same feeding grounds in the sea (as in 

 the sea nets they are caught together), present such variations 

 in appearance as to render the salmon from each river recog- 

 nisable at a glance. The conditions in the sea being, then, im- 

 partial, as open to the fish of different rivers, it must be the 

 sojourn of the fish in fresh water, where they are bred, that 

 influences their appearance, strength, vigour, and eating quali- 

 ties ; and a predisposition to take the disease may thus descend 

 by inheritance. 



The pollution of a water is generally supposed to favour 

 salmon disease, and the opinion is even prevalent that it can 

 originate it. The latter view is, of course, quite impossible, as 

 the origin of the disease is undoubtedly the spore or seed that 

 it grows from, and which can only be produced by the fungus 

 itself. The direct influence of pollution, in the present undefined 

 meaning of the word, is apparently of little real weight, when 

 we consider as a. fact that the cleanest water is as favourable to 

 the growth of the fungus as can be desired to account for its 

 ravages, and that the ordinary pollution of rivers from towns 

 or manufacturing sources would in all probability be more un- 

 favourable than otherwise to the fungoid growth. It is on 

 record that many of the cleanest rivers in the kingdom have 

 been the scenes of bad outbreaks of the disease. A case 

 occurred in Sheffield a few years ago, when as many as a 

 thousand trout died of fungus in a, reservoir that supplied the 

 town with water, the quality of which was certified by the City 

 Analyst to be quite as good as usual. The people of the town 

 were, indeed, drinking it all the time. 



We have also the fact that aquarium fungus is and always 

 has been common, even when supplied by the town pipe-water, 

 as aquariums usually are. Against this, consider that some of 

 our polluted rivers in the neighbourhood of the diseased are quite 



