2/8 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 



a seven-pound " Silver Trout " taken at Tahoe City, with the 

 ordinary henshawi, 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. 



