290 
FISHES. 
colour and brightness by living at greater depths, and 
further from the sun; changing in proportions and shape 
of the fins and tail, caused by the greater superincumbent 
body of water above, as it lives in deeper waters than its 
fly-feeding cousins nearer the surface. 
The very anatomy changes, as in variety " e " of our 
list ; and any one conversant with the marvellous changes 
and infinite varieties of S. fario already existent in New 
Zealand, or, as we are, conversant only with the fact as 
gathered from the late Dr. Arthur's and other New Zealand 
authors' papers, cannot fail to realise the vast power of 
isolation and natural selection. 
194. Salmo fontinalis, Mitchell. American Brook Trout. 
Introduced some years ago by his Grace the Duke of Suther- 
land, most of which were placed in Loch Brora, and a few 
in the Kintradwell burn ; we doubt if many, or indeed any, 
of these are now left. 
195. Salmo alpinus, L. The Charr. 
Common in some of the lochs throughout the county of 
Sutherland, and probably inhabits others where its presence 
is yet undetected, as the charr rarely takes a fly in most 
of the lochs, though there are exceptions, as we have 
caught occasional ones in Lochs Merkland, Griam and 
Shin, and Lochs Borrolan, Urigill, Camaloch, Veyattie, 
I'ewn, Assynt, and Brora, with fly, and more rarely with 
artificial minnow. 
The isolation of the charr in certain lochs on the shoulder 
of Ben Hope, in Sutherland, is a subject distinctly deserv- 
ing of the attention of naturalists, as indeed is the isolation 
of charr and trout in several other localities known to the 
writers of this account. Patient investigation of these 
