278 SCIENCE SKETCHES. 
not only in Lake Tahoe and its outlet, but in 
Humboldt River and in every suitable stream and 
lake in the Great Basin of Nevada, as its cousin 
virginalis is found in the Great Basin of Utah. 
As Lake Bonneville was drained to the north, so 
was Lake Lahontan to the northeast, and the 
great Snake River found room for all their 
waters. From its great resources, it stocked them 
all with trout, and the falling of the waters has left 
these trout to isolation and therefore to change. 
Another of these old lake basins is that of 
Southeastern Oregon, the “Lake Idaho” of 
geologists, including Malheur, Summer, Goose, 
and Christmas Lakes and their tributaries. In 
these many lakes and streams trout doubtless 
occur, and these have doubtless undergone modi- 
fications. But the varieties thus formed are yet to 
be studied and to be named. 
Coming back to the Colorado Basin, we find its 
trout spread far and wide in the mountain streams. 
Between the valley of the Colorado and that of the 
San Joaquin stands the great main chain of the 
Sierra Nevada, full of trout-brooks, made up of 
rocky walls which no trout can ever pass. To the 
southward this great wall breaks up into detached 
ranges now separated by Valleys of Death; fiery 
deserts and alkaline sinks, some of them below 
the level of the sea; burning wastes of cactus and 
aseven-pound “Silver Trout” taken at Tahoe City, with the 
ordinary Aenxshawi, and find no real or permanent difference. The 
Silver Trout are the large ones living in the depths and spawning 
in the lake. The Black Trout live near shore, and spawn in the 
stream. The Silver Trout may sometime become differentiated, 
but is not yet a separate species or subspecies. 
