Xll 



exceptional activity, or (2) the fish must have been rendered 

 exceptionally susceptible to its attacks. The first of these causes 

 is admirably illustrated by Professor Eolleston — the second by 

 Dr. Cooke — in the valuable papers which we have inserted in the 

 Appendix.* We can only say here that we do not consider 

 either of these theories quite established, and we pass on to the 

 question whether any remedies are applicable to the disease. 



On this point, however, a very material question arises which 

 we have not hitherto examined. The evidence which we received 

 during our inquiry pointed to the conclusion that the disease was 

 a freshwater disease or a disease which attacked the fish during 

 their sojourn in fresh water. Isolated cases indeed came before 

 us of fish taken in salt water with disease upon them. But in 

 all these cases the fish were taken in the estuaries or near the 

 estuaries of rivers, and there was reason to believe that they 

 had dropped down to the sea after they had contracted the 

 disease, and had not recovered. This conclusion was strengthened 

 by an experiment undertaken by the Tweed Commissioners. 

 They confined diseased fish in the brackish waters of the 

 estuary of the Tweed, and kept them till they recovered from 

 the disease. For all these reasons we were disposed to infer 

 that the disease was a purely freshwater disease. The remark- 

 able outbreak of the disease, however, which undoubtedly occurred 

 in the Aquarium at Southport, seems to shake this conclusion. 

 There can be no doubt whatever that an outbreak of Saprolegnia 

 occurred in the freshwater tanks of the Aquarium. There can 

 also be no doubt that a sea-trout in salt water, which had been 

 continuously in salt water for months, and had never come into 

 contact with fresh water, showed symptoms which in the judgment 

 of the Honorary Consulting Naturalist, Mr. C. L. Jackson, 

 and the Curator, Mr. Long, were precisely similar to those which 

 were displayed by the diseased fish in fresh water. We made 

 arrangements for ascertaining; whether the fish thus affected was 

 affected with Saprolegnia. But, in the hot weather of June, the 

 disease gradually disappeared from the freshwater tanks, and, at the 

 same time, the sea-trout also recovered. Two of us visited South- 

 port. The sea-trout then bore traces of the fungus. Its tail was 

 partly eaten away, and scars were visible on its head and on its body. 

 But the fungus had entirely disappeared and we were unable to 

 obtain any for microscopic examination. We cannot, therefore, 

 say that the fish in question actually had the Saprolegnia. But 

 there are prima facie grounds for suspecting that it had the 

 disease, and at any rate, with this doubtful case on record, we 

 hesitate to pronounce the Saprolegnia a purely freshwater diseasef. 



If the Saprolegnia can, under any circumstances, live in salt 

 water, the difficulty of curing the disease is obviously increased. 

 But, even in that event, the efforts towards eradicating it must 



* Appendix II., pp. 103, 113. 



f In this view Mr. Buckland does not concur. His individual opinion on this 

 particular point is separately expressed at the end of his Addendum to this Report. 

 See p. xxiii. 



