202 Transactions.— Zoology. 
waited for the “troubling of the water." Being unable then to fulfil the 
functions of nature at the spawning season, is the first contributing cause 
to the outbreak of the fungus. 
Again the chemical constituents of the water have an important bearing 
on the health of the trout. Trout under domestication when attacked by 
fungus have in almost all cases been cured by the addition of common salt 
to the water supplying the ponds or tanks containing the fish, provided the 
disease has not been permitted to go too far. As already mentioned, Dr. 
Black reports that the Wakatipu water has less salt in solution than any 
water ever examined by him. Now, as salt is an essential to health in 
trout, its entire absence in the water under consideration must act pre- 
judicially on these fish. This is the second and only known cause tending 
to accelerate the outbreak of the disease. But there is yet another cause 
which I suspect, although not in a position to prove, namely,—the absence 
of a due proportion of oxygen among the gases held in solution by the 
water. To determine this, not only is a gaseous analysis required, but it 
is also necessary to find out what that quantity of oxygen is which trout 
require. Science has yet to discover this ratio so far as I know, and it is 
an important element in its bearings on this question. As already stated, 
the fact of the trout seeking those places, as the mouth of the creek and the 
reef, where oxygen is likely to be most abundant owing to the constant 
agitation of the water, shows that the instincts of these trout teach them to 
look for water where the best aeration is to be found. 
These causes, then, seem to me sufficient to prove that the disease 
among the Wakatipu trout has been consequent on functional derangement, 
and that this has so lowered the vital force of the fish as to leave them 
powerless to resist the attacks of the fungus, a plant which the best authori- 
ties tell us is present in all fresh waters. 
Can the Disease be cured in the Wakatipu Fish ? 
And here I confess that, considering the unfortunate situation of these 
trout in Queenstown Bay, no ordinary remedy could be applied efficiently. 
For although the submergence of rock salt at the places frequented by 
the fish, and the artificial increase of the water supply to the Town 
Creek, might probably lessen the extent of the evil, yet these applica- 
tions could effect but a partial and temporary check on the disease. 
Moreover, there would be no finality to these operations, and their 
cost would exceed the means of the local Acclimatization Society I 
fear. No doubt it would assist if the trout were netted and all affected 
fish killed and burned; but in this there might be no finality either, 
still it ought to be done. While I am bound then to admit that I see 
no specific cure of an easy and cheap nature, there is yet hope, I think, 
