The Fungus of Salmon Disease. 65 



During epidemics of salmon disease in a river with prevalent 

 high water, immense numbers of spores are in all probability 

 deposited on the banks, and have better chances of remaining 

 there undisturbed than in other situations. When the waters 

 recede, and are followed by summer weather or other drying 

 influences, it would only be natural for dry spore distribution to 

 go on with every favourable wind, and I have no doubt this 

 happens, (See Note on pp. 64, 65.) 



The conditions for the favourable growth of salmon fungus 

 are not many, nor is the fungus as difficile as some kindred 

 organisms. The first essential condition is the quality of the 

 water in which the growth is to take place, and its full aeration ; 

 next, a proper solid nidus, containing the necessary suitable 

 nourishment that can be quickly assimilated ; and the third 

 requisite condition is a suitable temperature. 



The purity or impurity of the water is an important factor, 

 but I am not able to agree with the usual view that impure or 

 polluted water is distinctly favourable to the disease ; in fact, 

 my experience is exactly the reverse, and I know of no re- 

 liable evidence that can be justly considered to favour such 

 a supposition. As I shall have more to say on this subject later ? 

 I have only to add briefly here, that pure spring water taken at 

 its source invariably gives results of growth that, for favourable 

 and plenteous development, are enough to satisfy anybody. 



The proper aeration of the water is absolutely necessary. 



servation which at the time gave such positive results. I am aware that contamination 

 may have been conveyed by the water used, or the flies that were employed to culti- 

 vate upon, and in confirmation of such a possibility, I may mention that I have twice 

 had an invasion of Achlya in my cultures of salmon disease, and which must in one 

 case have come from the flies used, as the water was previously sterilised by boiling, 

 but this would tend to confirm the experience rather than otherwise. 



Of course, it must be understood that, in order to obtain such a result as the one 

 detailed, the zoospores would need to be in their second stage of full maturity before 

 drying. 



In the wet condition, I have lately had very vigorous and ready development from 

 the zoospores of an intentionally neglected cultivation of salmon disease fungus, after a 

 period of more than thirty days. 



