exposed, and the fins are eaten away, and become ragged 

 Very often one or both gill-covers become partially glued 

 down to the shoulder, and the gill-openings obstructed, but 

 I have never yet been able to meet with any sign of disease 

 on the gills themselves. This is contrary to common belief, 

 but I can only say that such is my experience. On the 

 other hand, the disease frequently invades the cavity of 

 the mouth, and often more or less destroys the mem- 

 branous veil which lies behind the teeth, and plays a 

 curious part in respiration. Thus, although, so far as I have 

 been able to observe, the respiratory organs are not 

 directly attacked, the performance of the respiratory 

 function may be very seriously obstructed. 



If the mucous membrane lining the mouth be reckoned 

 with the integument, of which it really is a part, it. may be 

 said that the affection under discussion is strictly a 

 cutaneous disease, comparable to ringworm among men. 

 However badly a fish may have been diseased, there is no 

 trace of the affection in the abdominal cavity or in any of 

 the viscera, and the muscles and deep-seated bones appear 

 healthy. Some say that the liver is enlarged and soft, but 

 I have seen the liver quite healthy in very severe cases. 



The fish appear to suffer considerable irritation from the 

 disease ; but how far this is a primary symptom, and how 

 far it results from the entanglement of multitudes of 

 minute grains of sand in the fluffy coat of the diseased skin, 

 is uncertain. Badly diseased fish in aquaria, the water of 

 which contains no suspended particles of sand, do not show 

 signs of any particular irritation. 



The mortality among salmon, sea trout, and freshwater 

 trout caused by this disease is very considerable. In the 

 last five years from 2000 to 4000 diseased fish have been 

 taken out of the Tweed, and a like number out of the 



