of the Fishery Board for Scotland. 



371 



This however, is an erroneous theory, because certain gastro-intestinal 

 conditions which are always followed by a diminution of mucus secretion 

 tend to make the fish more susceptible to fungus growth. 



Fish sometimes present a most disgusting appearance when the disease 

 is much advanced, the flesh being almost entirely rubbed off in certain 

 situations, as over the nose, crown of the head, opercula, and skin covering 

 the fins. I have seen a fin almost entirely denuded, with the rays stand- 

 ing out quite separate from each other. 



If one examines a fish in the early stage of the disease the patches have 

 a peculiar appearance, as the fungus falls when the fish is removed from 

 the water. On close inspection such a patch appears as if denuded of 

 scales, but a little gentle rubbing removes the fungus, and it is then seen 

 that the scales are so far intact. 



On parts naturally devoid of scales, the diseased areas look as if they 

 were produced by injury, and are not at all unlike as if due to bruises, 

 having a somewhat darker colour than the healthy skin. Here also by 

 gently rubbing one may manage, in some cases where the disease is slight, 

 to completely remove all visible signs of the fungus. It has been already 

 remarked that the very early patches are usually almost completely 

 circular, but, as the diseased areas extend, new foci are formed and the 

 patches become irregular, and still later by the blending of several 

 previously discrete patches, the irregularity is made worse. On attempt- 

 ing to rub off the fungus covering an older patch, it may be found that 

 the epidermis below has completely disappeared, and an ulcerating or 

 granulating sore is left. The appearance presented by a young patch 

 when examined in water is rather pretty than otherwise, as the fungus 

 can be observed standing up like wheat in a field ; but in the older, the 

 threads of the fungus become intertwined, and enclose in their meshes 

 bacteria, diatoms, particles of dirt, &c* 



After a diseased patch has once appeared it extends for a day or more 

 and then frequently many other patches make their appearance, and the 

 disease then progresses rapidly. 



In advanced cases, not only may the bones of the head and fins be 

 denuded of skin, but blindness f may, in some cases, ensue from the 

 fungus attacking the eyes. I have not, however, seen such a case; 

 contrarily I have observed in the case of a char, disease progress from the 

 snout to the regions beyond the eyes, but leave the pupil quite 

 untouched, although it was adherent to the skin all around it. Probably, 

 in this case, it might have extended to the eye, but the fish died at this 

 period. Even after death, however, in this specimen, as also in the case of 

 a gold fish and a minnow, the pupil remained quite unaffected. Fre- 

 quently the fungus extends into the mouth and forms a tangled mass 

 over the teeth, and usually also affects the membrane covering the floor 

 and roof of the mouth itself, more especially that in the floor, forming, in 

 this way, a decided obstacle to respiration. I have only in one case 

 observed the gills affected, and in this case there were present several 

 parasites adhering to the gills and being themselves affected by the fungus. 



Fish soon after becoming affected show many evident signs of irrita- 

 tion, rushing about in a most erratic manner and leaping out of the water. 

 They may also be seen to rub themselves against rocks, as if attempting 

 to effect the removal of the parasite. Probably this accounts for much 

 of the injuries one finds on such fish, which may thus be held to be self- 



* Animal Report of Scottish Fishery Board, 1886. 



t Bacteria are also found inside the tubules of the fungus itself, but this seems in 

 most cases to be due to degeneration taking place in the particular hypha, as they 

 are not usually seen in healthy hyphse. 



