97 
cuting through a series of years these investigations upon the 
life of the Ilinois River, a problem for whose solution private 
enterprise and even the usual university facilities are quite in- 
adequate. To him I wish also to make acknowledgment for 
his valuable directions, suggestions, and encouragement 
throughout the whole course of the work. To my colleagues 
of the State Laboratory staff acknowledgments are due for co- 
operation in manifold ways. The collections of the period 
preceding July, 1895, were made by Professor Frank Smith 
or under his direction. He also devised the “oblique-haul” 
method of collection, and has rendered assistance by the identi- 
fication of aquatic oligochetes. A portion of the field work in 
1894, 1895, and 1896, was performed by Mr. C. A. Hart and Mr. 
Adolph Hempel. To the former I am indebted for clerical ser- 
vices and for assistance with the aquatic insects and the mol- 
lusks; to the latter, for some data concerning the rotifers and 
the Protozoa. During the last seven months of our operations 
the field work was faithfully attended to by Mr. Wallace Craig. 
Acknowledgments are also due Mr. Miles Newberry, who from 
the beginning to the end of our operations served, in summer’s 
heat and winter’s cold, as field assistant in the work of col- 
lection. His faithfulness and skill in dealing with the frequent 
difficulties and the occasional dangers of the river situation 
have added not a little to the success of our work. Iam under 
much obligation to Mr. R. E. Richardson (of the class of 1901, 
University of Illinois) for most efficient clerical assistance in 
the laborious task of the counting work and in the compilation 
and organization of the. statistical data resulting therefrom. 
From Captain J. A. Schulte, Mr. J. M. McHose, and the city 
authorities of Havana the Station has received many courte- 
sies. Hon.J.M. Ruggles and County Superintendent M. Bollan, 
of Havana, have also rendered favors by way of information on 
various points. To many other correspondents I am under 
obligation for courtesies, and not the least to Mr. G. A. M. Lil- 
jencrantz, of the office of U. 8. Army Engineer of Chicago, for 
oft-repeated contributions of hydrographical data, 
