NATURAL HISTORY NOTES 71 
Sapolegnia ferax is one of these moulds and first cousin to the same 
organism is Achlya prolifera which, I believe, is the direct cause of 
Salmon disease. Achlya grows parasitically on the bodies of dead 
flies lying in water and it is obviously but a step from this to the 
Salmon for it is quite conceivable that a stagnant pool in a river on 
or near which considerable hatches of flies took place might become 
infested with the spores of the organism, their new nidus being the 
skin of the living fish. 
Some years afterwards I saw that the same or a similar disease 
was affecting the grayling in the Wye between Rakewell and Haddon 
Hall: some very large fish were seen dying and dead. The general 
appearance cf the diseased fish being that of the salmon in the Usk - 
there can be little doubt that the malady was the same as also the 
general causes which led to the outbreak, viz.,a low river for a 
lengthy period and consequent increase of contamination ; the sowing 
of the mould into the stream by insects and probably the passage of 
such insects through the digestive tract of the fish, whilst the 
evacuations of the fish might greatly foster the trouble. From what 
I have observed I should think that the trout is not nearly so 
susceptible to the disease as the other fish mentioned—I have never 
seen an indisputable case amongst trout. It suggests itself that 
Some antiseptic treatment might be carried out in an affected river— 
something which would restrict the mould srowth without injuring 
the fish. A salt of copper very carefully applied might prove 
successful. ; 
An incident of the little campaign on the Usk, which I recall] 
with some pleasure, was seeing an otter face to face on one of the 
scours. It was in the dusk, but the surface of the water was plainly 
visible with the western sky as a back vround. Whilst pausing for a 
few moments in casting, there rose from the sandy shoal] at a distance 
of perhaps ten paces an object which at first view looked like a black 
baby. Just as I had made out what it really was, it slid noiselessly 
back into the water and was gone. I found subsequently that the 
animal had shewn itself in a somewhat similar manner to my friend 
who was fishing further down the river-— it had given him quite a 
“start,” having come much nearer to him than to me. 
Turning to an entirely different subject. How many people 
who have spent much time in open country must have been struck 
by the curious movements of birds when flying in flocks. Starlings 
