ArtHUR.—On the Brown Trout introduced into Otago. . 501 
out of their stomachs, as related by me above, and they are known or sup- 
posed to have killed and eaten trout about 2 lbs. in weight. The ordinary 
shag of our rivers is about as big as a tame duck, but much thinner in body 
having a long sinewy neck and a dreadful bill with a hook at the point. 
Disease at our Opoho hatchery among the ova is unknown. Dead eggs 
have been found to be unimpregnated, and no loss has resulted from silt, of 
which there is always a good deal. Deaths among the young fish have been 
consequent on a dropsical affection of the umbilical sac, and of monstrosi- 
ties. Having already made some remarks on very thin male trout which 
appeared to be “dying by inches,” in consequence of their flesh and fat 
consuming away, 1 will not add more than the suggestion that fever would 
account for the symptoms or effects of their ailment. Several specimens 
of trout found dead in our rivers have come under my notice. Dissection 
showed that some internal organ as the intestine was ruptured, but how oc- 
casioned it would be hard to say. For several years Mr. Nelson has seen 
trout in Lovell's Creek which were quite blind. This he proved repeatedly 
by trials; yet when a worm or bait was thrown into the water they took it 
at once. These trout were of both sexes, 4-5 lbs. in weight, not by a long 
way the largest trout in the stream, and their eyes had white opaque spots 
on each. In the case of females, the ova were found at the spawning season 
to be bad, although the fish were in good condition. No cause has been 
found out for this singular eye affection, but probably its origin is parasitic. 
Fungus, unfortunately, is not unknown in Otago waters. It was noticed 
first on trout in confinement at the Wallacetown ponds, by Mr. Howard, 
about 1874 or 1875. During spawning it has been seen on trout in Fulton’s 
Creek; but in Queenstown Bay, Lake Wakatipu, it ig very prevalent among 
the shoals of trout there, as formerly described by me.* The pathology (to 
borrow a medical expression) of this disease has not yet been worked out 
exhaustively, and it is surrounded by many difficulties. At the same time 
I may be pardoned if I again give my opinion, that all the exciting causes 
of the affection may be narrowed down to two conditions, viz.:—the absence 
of sufficient salt in the water inhabited by the fish, and of sufficient oxygen 
in the blood of the fish itself. Salt has been found to be a wonderful health 
promoter among the Salmonide; and oxygen, in the necessary proportions 
in the blood of the fish, is indispensable to secure it from fungoid attacks. 
Trout in Shag River have died, as supposed, because of excessive heat. 
; ILL — Structure. 
Although external colour and markings can scarcely be referred to struc- 
ture, yet these come more naturally under that heading than any other. 
Specimens of trout from High Wycombe, Bucks, are thus described by Mr. 
* Trans. N.Z. Inst., 1882, vol. xv., p. 198. 
