6— A PRELIMINARY REPORT ON THE AOUATIC INVERTEBRATE FAUNA 
OH THE YELLOWSTONE NATIONAL PARK, WYOMING, AND OF THE 
FLATHEAD REGION OF MONTANA. 
BY S. A. FORBES, 
Professor of Zoology, University of Illinois. 
INTRODUCTORY. 
The immediate impulse to the investigation of the aquatic invertebrate fauna of 
Wyoming and Montana, here reported in a preliminary way, was supplied by the 
ichthyological work of Dr. David S. Jordan, in the Yellowstone National Park, in 
1889, and of Prof. B. W. Ever maun, in Montana and Wyoming, in 1891. 
The waters of Yellowstone Park had been reconnoitered by Dr. Jordan for the 
special purpose of ascertaining precisely which of them were destitute of fish and 
what was the cause of their barrenness. This having proved to be topographical in 
every case — some physical barrier to the entrance of fishes from below— it seemed 
possible to stock these waters permanently with valuable game-fishes, and thus greatly 
to increase the attractiveness of the Park to a considerable class of travelers. Pre- 
liminary to this, however, it was evidently desirable that a full knowledge should be 
had of the variety and abundance of the lower animal life of these fishless waters, 
since upon this the fishes introduced must chiefly depend for food. To this practical 
end it was the wish of Hon. Marshall McDonald, United States Commissioner of 
Fish and Fisheries, that my own investigations made in 1890 should be immediately 
directed ; but with the understanding that the opportunity thus afforded for a general 
zoological survey of the waters of Yellowstone Park should be improved to the best of 
my ability. 
My associate in 1890 was Prof. Edwin Linton, of Washington and Jefferson College, 
Pennsylvania, who, although specially charged with another duty, that of a study of 
the parasites of fishes in these waters, rendered me constant and invaluable service in 
my own special field. 
In 1891 it was my general purpose to cooperate with Prof. Evermann in an 
exploration of the waters of Montana and Wyoming, to be made with reference to 
the location of a fish-hatchery; but in this, as* in the preceding year, I made every 
effort to become as thoroughly acquainted with the animal life of the waters which 
I examined as the brief time spent iu each locality would permit. 
207 
