12 



but overflow/t'il afjain from the rivei' at every slight rise. Phelps Lake, on 

 the other hand, serves as an example of the highly variable conditions pre- 

 vailing in a pool filled up at every general overflow, but isolated on the re- 

 treat of the waters, and di-ying out entirely in the very driest years. 



ESSENTIAL OBJECTS. 



It is the genei-al. comprehensive object of our Biological Station to stuily 

 the forms of life, both animal and vegetable, in all of their stages, of a gi*eat 

 river system, as represented in carefully selected typical localities. This 

 study must include their distinguishing characters; their classification and 

 variations; their local and general distribiation and aVjundance; their be- 

 havior; characteristics, and life histories: their mutual relationships and inter- 

 actions as living a-ssoeiates; and the intei'actions likewise between them and 

 the inanimate forms of matter and of energy in the midst of which they live. 

 We are, in short, to do what is possible to us to imravel and to elucidate in 

 general and in detail the system of aquatic life in a considerable district of 

 interior North America. 



So vast a subject nu;st of course be intelligently divided and studied i>art 

 by part, in some systematic order, to avoid a dissipation of effort and to in- 

 sure the speedy attainment of some definite and tangible results. Its most 

 olbvious divisions ai'e the systematic, the biographical, and the oecological: 

 and this is the order, broadly speaking, in which the general investigation 

 must be carried on. Both systematic and biographical biology have a high 

 independent value in our scheme, but both are with us chiefly means to the 

 remoter end of a study of the interactions of associate aquatic organisms, ami 

 of their relations to nature at large. It is thus the oecological idea which is 

 to lead in the organization and development of our work. A systematic sui'- 

 vey of the biological assemblage is a necessary preliminary step and the 

 tracing of life histories and the recognition and description of immature 

 stages is a scarcely less essential prerequisite; for without the knowledge 

 which these studies are to give us, it would be obviously impossible to make 

 any comprehensive study of variations, distribution, and (ecological relation- 

 ships. 



The oecology of the Illinois Hiver is greatly complicated, and the difficulty 

 of its study intensified, by certain highly and irregularly varial>le elements of 

 the envii-onmeut. Apart from those secular and moi'c or less inconstant 

 features of climate and Aveather which nuist be tnken into account wherever 

 s\ich studies are prosecuted, we often have here the evidently very large and 

 highly intricate reactions produced by periodic variations in the river level, 

 and the consequent eiun-nKms extensions and corresponding diniinution?; 

 of the mass of the waters and of the area covered by them. Fortunately 

 for the possibilities of success in so difficult a field, progivss in it does not 

 reqilire that the entire system of life should be studied as a unit at first. 

 Spt'cial i>rdl)lems may be selected, of a kind to be brought easily within the 

 Available time and the capacities of the individual investigator, which, being 

 worketl out one by one, may be later bnnight together as contributions to a 



