HOW THE TROUT CAME TO CALIFORNIA. 279 
greasewood, enlivened only by the rattle of the 
Sidewinder. In the glacial period this region had a 
different climate. Melting ice once filled the terri- 
ble deserts of Amargosa and Panamint with sweet 
waters. In some way or other this region may 
have been traversed by the trout. I once thought 
that from the Colorado to the Kern! the trout must 
have come into California. It may beso; but if our 
theories follow the line of least resistance, there is 
an easier way. If the trout came from the Colorado 
to the Kern, it has in the transition lost most of the 
red of its cut-throat mark, but not all of it. The 
scales became somewhat larger, the red band on 
the side more distinct, and the spots extended for- 
wards. In all these regards we come nearer to the 
trout of the Walla Walla region, the one we call 
Salmo mykiss gibbsit; and while it is possible that 
.the Kern Trout (g2/derti) came from the Colorado 
trout (pleuriticus), which they greatly resemble, my 
present impression is that they did not. 
Let us try this supposition. The old mykiss 
stock filled the Columbia. After the lava flows 
had formed Shoshone and American falls, the trout 
of the Upper Columbia (/ew7s?) were shut off from 
the others. Perhaps the waterfall of the Cascades 
separated those of the Middle Columbia from those 
of the lower portion of the river. In any event, the 
gibbsti became somewhat different, losing in part 
its cut-throat mark, and passing into the small- 
scaled white-throated form we call the Steel-head, 
1 The Trout of Kern River is Salmo gairdneri gilberti Jordan, 
named for its discoverer, Dr. Charles H. Gilbert, who has been 
for twenty years my colleague in the study of our fishes. 
