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Proceedings of the Royal Society 
which it was affected, it had returned to the river in such a 
mutilated condition, and with unhealed sores of such a nature, as in 
all likelihood would have ultimately proved fatal. Besides, the fact 
that the fungus was not killed by the salt water, but was found in 
a highly vigorous condition on the parts to which it still adhered, 
gives but small hope of any permanent benefit to diseased fish from 
a visit to the sea. 
The fungus belongs to Saprolegnieae, a natural order of doubtful 
affinity — said to have the habits of moulds and fructification 
algae. This order consists of the genera saprolegnia and achlya, 
which are great enemies of fish and other animals preserved in 
aquaria. 
The filaments of the fungus arise free from the outer surface of the 
epidermic layers of the fish, having neither branches nor articulations. 
They are tubes, the walls of which are perfectly translucent, and in 
their interior at irregular intervals are small groups of fine granular 
matter. 
The majority of the filaments are spear-shaped at their upper 
terminations, and appear to be barren. 
The prolific filaments, on the contrary, enlarge at their upper 
extremities, and form elongated club-shaped chambers, in which 
granular matter gathers. In the midst of this granular matter small 
round bodies appear, and those enlarging, gradually develop into 
spores. The prolific filaments apparently contain more granular 
matter, and are of greater calibre than the other filaments. They are 
evidently destined from the first to be the propagating media. 
The spores escape by an opening in the summit of the chamber. 
This aperture is not an original opening. It is produced in a some- 
what remarkable manner — so long as the spores are unripe and unfit 
for expulsion, a slender continuation of the filament projects from 
the apex of the chamber in manner similar to the neck of a bottle. 
At the point at which this joins the spore-sac, there is a slight 
contraction, which goes on gradually increasing in depth. Ultimately, 
when the spores are fully matured it drops off, and the aperture is 
formed. The filaments forming the mycelium of the plant are 
tortuous and branched ; they ramify in the mucous and epidermic 
layers of the fish ; they do not penetrate the corium where there 
are no scales. In other situations they never reach a greater 
