In the preparation of this paper there have been two purposes in mind. One of these is the presentation of the results of studies thus far made on the fresh-water sponges of lllinois ; and the other is to assemble in more convenient form the information which we now have concerningthe distribution of such sponges in North America. Preliminary to the more detailed presentation of data it is desirable to give a brief summary of our knowledge of the fresh-water sponges of this continent.