of the Mshery Board for Scotland. 



379 



on cither aide. Largo patches existed at the posterior border of the 

 opercula, and passed thence to the posterior insertion of first dorsal 

 fin over which it extended half way to its tip. The upper half of the 

 tail had an extensive growth, and there existed a small single patch on the 

 tip of the right pectoral fin. On opening the mouth the fungus was 

 seen to form a close-felted mass over the teeth, and passing thence to the 

 lining membrane of the mouth, which it alfected to a distance of one inch 

 beyond the teeth, but extending a little further in the mesial line of the 

 lower jaw. Both gills were slightly affected, and here there were found 

 several parasites, which were themselves diseased. The viscera showed 

 no visible signs of disease, with the exception of the spleen which was 

 congested, but not much enlarged. The fungus was somewhat similar to the 

 common S. ferax, and as the mass in the mouth contained growing 

 zoosporangia, I endeavoured to obtain cultivation from the contents of the 

 intestinal canal, and have at length succeeded. Here then we have a case 

 of infection occurring without any suspicion of overcrowding. I have 

 traced the origin of the disease in this case, either to a hatching box 

 suspended near the tank, and from which several young embryos were 

 removed several days before, affected with the disease, and it is possible 

 that when cleaning this box some material was allowed to fall into the 

 larger tank, thus determining the infection of this fish ; or to there 

 having been disease in this tank during a previous year. The 

 problem as regards infection of river salmon is somewhat difficult to 

 solve. The disease exists while salmon are in the water, and disappears 

 on their departure. Thus it would seem that they bring it with them, 

 but I have the reliable observation of Mr Johnston, the lessee of the 

 Esk fishings, to show that the disease always first makes its appearance 

 in the higher reaches of the river an d subsequently comes down. This 

 would indicate that the infection is met with in the higher parts of the 

 river, and that the fish are healthy when they leave the sea. This is 

 somewhat emphasised by the experiments made by Mr List, for Mr 

 Stirling and later for Professor Huxley, and by those of Mr Armistead 

 of the Solway fishing, Dumfries, and by that of Mr Johnston of 

 Montrose. In all these experiments it has been found that if diseased fish 

 are placed in salt water they tend to recover, and their sores, if there be 

 any present, to heal, indicating that it is improbable that the disease is 

 brought from the sea. Further Sir James Maitland informs me that at 

 the Howietoun fisheries the fungus can always be controlled by the addition 

 of rock salt to the water in the upper ponds. 



If then we assume that the disease is contracted by the fish in the 

 higher reaches of the river, where does it remain during those months 

 when no salmon are in the river 1 It may be said that it attacks trout, 

 and that therefore we should find it during the summer affecting them. 

 I do not know, however, that it is a well-ascertained fact that trout are 

 generally liable, and farther we do not possess reliable evidence to show 

 that the fungus attacking trout in summer is the true JS. ferax. 



Having obtained, by the kindness of Mr Johnston of Montrose, a fine 

 salmon heavily coated with the fungus, I determined to attempt tli?3 in- 

 fection with it of some healthy gold-fish, as from multifold observation, 

 such fish seem to have acquired it naturally when kept in aquaria. For this 

 purpose large portions of the fungus, in which a plentiful growth of spor- 

 angia was present, were placed in a large glass vessel of water in which three 

 gold-fish were present. In another vessel the same procedure was adopted, 

 but here, in addition to the gold-fish, three minnows were also placed. In 

 neither case, however, did any successful result accrue, while in the case of 

 the minnows I found that they devoured the fungus greedily, ejecting the 



