THE DISTRIBUTION OF SPECIES. 205 
miles long and two hundred wide. For days they passed 
in clouds that darkened the earth with the gloomy hue of 
an eclipse, while the ground was covered with crawling 
millions, devouring every green thing, and giving to the 
country the appearance of being carpeted with scales. 
It has been discovered, however, that before they attain 
their winged state they can easily be destroyed, and en- 
ergetic measures will be taken against them throughout 
all the inhabited districts of Australia whenever they 
make another appearance.” (Station Life in Australia, 
Scribner’s Magazine, February, 1892, pp. 136-154.) 
I was lately called to examine a specially interesting 
problem in geographical distribution, that of the disper- 
sion of fishes in the Yellowstone Park. 
This region is a high volcanic plateau, 
formed by the filling of a mountain basin 
with a vast deposit of lava. The streams of the park are 
for the most part among the coldest and clearest of the 
Rocky Mountains, and apparently in every way suitable 
for the growth of trout. All the hot springs of the great 
geyser basin are not sufficient to warm the waters of 
the Firehole River. Yet, with the exception of the Yel- 
lowstone itself, all these streams are destitute of fish life. 
A reason for this is apparent in the fact that the plateau 
is fringed with cataracts which no fish can ascend. Each 
stream has a cafion and waterfall near the point where 
it exchanges the hard bed of lava for the rock below. 
So the best of trout streams, for an area of fifteen hun- 
dred square miles, are left without trout, because their 
natural inhabitants can not get to them.* 
Trout in Yellow- 
stone Park. 
* Since this was written, the principal waters of this region 
have been stocked with trout of different species, and these have 
multiplied with great rapidity. There is now an abundance of 
trout in the Firehole, Gibbon, Gardiner, and Lewis Rivers, as well 
as in Shoshone Lake. 
