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cuting through a series of years these investigations upon the 

 life of the Illinois 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 oligochsetes. 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. I am 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. S. Army Engineer of Chicago, for 

 oft -repeated contributions of hydrographical data. 



