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but overflowed again from the river 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 drying out entirely in the very driest years. 
ESSENTIAL OBJECTS. 
It is the general, comprehensive object of our Biological Station to study 
the forms of life, both animal and vegetable, in all of their stages, of a great 
river system, as represented in carefully selected typical localities. This 
study must include their distinguishing characters; their classification and 
variations; their local and general distribution and abundance; their be- 
_ havior; characteristics, and life histories; their mutual relationships and inter- 
actions as living associates; and the interactions 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 unravel 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 must of course be intelligently divided and studied part 
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 
obvious divisions are the systematic, the biographical, and the cecological: 
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, and 
of their relations to nature at large. It is thus the ecological idea which is 
to lead in the organization and development of our work. <A systematic sur- 
vey of the biological assemblage is a necessary preliminary step and the 
tracing of life histories and the recognition and description of immature 
stages 1s a searcely 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 cecological relation- 
ships. 
The cecology of the Illinois River is greatly complicated, and the difficulty 
of its study intensified, by certain highly and irregularly variable elements of 
the environment. Apart from those secular and more or less inconstant 
features of climate and weather which must be taken into account wherever 
such 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 enormous extensions and corresponding diminutions 
of the mass of the waters and of the area covered by them. Fortunately 
for the possibilities of suecess in so difficult a field, progress in it does not 
require that the entire system of life should. be studied as a unit at first. 
Special problems may -be selected, of a kind to be brought easily within the 
available time.and the capacities of the individual investigator, which, being 
worked out one by one, may be later brought. together as contributions to a 
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