731 
of Edinburgh, Session 1877-78. 
depth than the outer surface of the scales ; they are tubular, the 
whole plant being without septa forms a single individual of 
apparently indefinite extent. The spores are variously shaped at 
different stages, ovate and kidney being the commonest forms. They 
are very minute, and require a power of 450 to observe them well. 
The cilia are two in number, a longer and a shorter one, and are 
situated at the long axis of the spore. They are difficult to observe, 
and always disappear in permanently mounted preparations, although 
the spores themselves remain unaltered in all other respects. When 
the fungus is stained with logwood or picric acid, excellent 
permanent preparations can be got. It has been stated that the 
fungus dies with the fish. I have not found this to be the case; on 
the contrary, all my observations have been made from dead fish. 
Some of the specimens sent me from Carlisle by Mr Dunne were 
mis-sent to Aberdeen, and returned to me on the seventh day after 
the death of the fish, and yet I have scores of permanent prepara- 
tions from these specimens, which show distinctly the characteristic 
form of saprolegnia ferax. 
I have also found the fungus perfectly identical in ail the 
specimens I have examined, which consist of salmon, sea trout, and 
river trout from the Eden, and salmon and grayling from the 
Mth. 
It has also been said that a salt solution destroys the fungus, 
“which, melts in the solution like sugar in ivater .” On the contrary, 
salt and water is an excellent preservative of saprolegnia ; masses of 
it before me as I write have been in a salt solution for two months, 
and it remains unaltered. Further, the salmon captured in 
the Nith, which is believed to have gone to the sea in order to 
get rid of the fungus, had the fungus growing vigorously on several 
parts of its body. The fungus must either have instantly attacked 
the fish on its return to the river, or not have been destroyed during 
its stay in the salt water. 
Regarding the cause of the disease, I can offer no opinion further 
than that some functional condition of the fish seems necessary for 
the propagation of the fungus. The germs of saprolegnia ferax 
must exist at all times, and in many places; and if so, there must 
be a reason why fish are not constantly affected with the fungus and 
in every river. I am persuaded that the condition of the fish 
