Arruur.—On the Brown Trout introduced into Otago. 981 
and water during each day of the fishing season, it was found that most 
salmon were killed with the rod on Loch Tay when the difference in tem- 
perature did not exceed 2° Fah.; but when it became as much as 5°, the 
fish ceased to take altogether. Although fish are cold-blooded animals, 
this would appear to indicate a certain degree of sensitiveness to variations 
in temperature. It is not so easy to account for trout and other species of 
the Salmonidz being aware (to use a common expression) when the baro- 
meter is falling before rain, as I have stated already. But one thing I am 
convinced of is that they do feel when the atmospheric pressure on the 
water alters to an appreciable extent. They get sluggish, and will not 
move to feed when the air becomes rarefied. But when the weather begins 
to change and clear up they soon move about again and resume feeding. I 
explain this on the supposition that, in the first instance, the fish feel their 
bodies sensibly heavier, so as to indispose them to move; but when the 
atmosphere regains its normal pressure, they are relieved from the sensation 
of weight, and their ordinary lively habits are resumed. Other animals— 
human beings included—are affected by the very same cause. This is, no 
doubt, rather a speculative part of my subject, and I could easily enlarge 
my remarks on it, but probably I have said enough for the present. 
4. Distinguishing Marks of Trout. 
This brings me to the concluding and more technical portion of my paper, 
but before going into that I think it will be better to record my examina- 
tions of a number of specimens of S. fario, which were caught in some of 
those rivers which I have already frequently referred to. From various 
causes my notes are not so complete as they should be, but still I give them 
just as they are. They may be useful for comparison and reference. 
: Specimens of Salmo fario examined in Otago. 
a.—1877, Nov. 30th.—Male trout caught in Lee Stream—the gorge 
water—with grasshopper, the river being very low. Condition thin, head 
long, and lower jaw hooked; colour, brown on back, golden on sides, 
numerous black spots and large red ones, a few being beneath the lateral 
line. 
Dimensions: Weight, 5lbs.; length, 25 in.; depth, 6 in.; head, 6} in.; 
maxillary bone projecting } in. behind the vertical from posterior margin 
of orbit; sixteen round black spots on gill-cover, one side. Teeth, vomer 
three firm five loose, palatines each well armed with teeth, tongue also, and 
with two small teeth loose near the tip. 
Fin Rays: P.14 on each fin; C.21 (doubtful), Scales: 16 in trans- 
verse row from adipose fin backwards to lateral line. Pyl. ceca: 54. 
Contents of stomach: crayfish, 2 in. long, and remains of larger one; three 
legs of a grasshopper and part of a black beetle, ái 
