The Fungus of Salmon Disease. 67 



cold water, a dead fly is put in the glass along with the fungus, 

 and the water is then changed once in every twelve hours until 

 a growth of the fungus is observed on the fly ; the original 

 piece of fungus from the fish may then be thrown away. It 

 may take two or three days in cold weather, or one day in 

 summer, to produce a visible growth on the fly, but when once 

 it is started the development of the fungus on the fly is very 

 rapid, and goes on until the seeds of the growth are distributed 

 through the water ; and as these seeds or spores are ready to 

 germinate again, if another fly be put in the water, it soon be- 

 comes infected like the first, and the cultivation is thus carried 

 on from generation to generation with absolute regularity. 



All fungoid life is liable to be suppressed in the struggle for 

 existence by other kindred organisms, or such other life as can 

 go on and develop side by side with it. It is, therefore, the 

 kind of life that is best suited to the conditions supplied to 

 it that succeeds in the struggle, and for this reason our fungus, 

 as cultivated in common drinking tumblers, requires watching. 

 If the water is not changed frequently, the conditions, at first 

 favourable, will become altered owing to the development of 

 other life, such as infusoria and bacteria, both of which con- 

 tinually grow and multiply side by side with the salmon fungus 

 culture, and if they were allowed to remain they would use up 

 the oxygen and feeding stuff in the water, and actually consume 

 the fungus itself, while also causing ill-smelling products to 

 collect that are likewise quite unfavourable to the fungus. By 

 pouring off the water, the unfavourable organisms, which are 

 generally free and moving in the liquid, are carried away with 

 it, and by repeated washing they are reduced to such a minority 

 that the fungus, which is attached to the fly and living on it, 

 easily keeps the upper hand, and with a fresh supply of well- 

 aerated water it continues to develop freely. 



There is absolutely nothing disagreeable in these cultivations 

 of the salmon disease fungus, which can be carried on in any 

 number of glasses in a small room. If any bad smell arises it 

 is always due to the development of bacteria or infusoria, 



