142 THE ESSEX NATURALIST.
cent, of the membership of such societies have anything but
the vaguest ideas on these points, and in the belief that more
widespread knowledge will lead to greater activity in this field,
I venture to refer to some of the problems which are still in need
of investigation.
As the basis of nearly all further scientific work, especially
ecological work, with which we are most concerned, is the accurate
determination of species, and even varieties in some cases, it is
evidently of the greatest importance that complete records of
as many groups of organisms from as many different localities
as possible should be made. As regards the Essex waters, a good
deal of this kind of work has of course already been carried out,
but in no case can we consider the work as complete, and what
has so far been accomplished is but a small fraction of what still
remains to be done. Many groups of organisms, especially
among the smaller forms, have scarcely been touched.
The need for additional workers who will take up limited
groups of aquatic organisms as their special study is therefore
apparent. Even if they confine themselves to the purely
systematic work of identification of species they will have this
advantage with aquatic organisms that their chances of dis-
covering new species will be much greater than with terrestrial
forms, owing to the fact that less is known about the former
than the latter, and their knowledge will also be invaluable in
such general ecological work as may be undertaken by otheis.
But it is practically impossible for anyone who collects and
examines living material to remain solely a systematist. Facts
concerning the habits and the relations to the environment of his
particular charges will force themselves from time to time upon
his notice, and it is in this way that lines of further biological
work are often suggested and valuable additions to the general
body of ecological knowledge obtained.
Apart from the determination of the species, the problems
of aquatic biology, so far as a Field Club is concerned, can all
be classified in a general way as ecological, i.e. they are all
connected with the study of the living organisms in their natural
environment. There are, however, several categories of such
problems, and we may, perhaps, for our immediate purpose,
group them in the following way : (1) the occurrence and habits
of the individual species, (2) the relation of the organisms to