We take pleasure in reproducing in this number the text and illustrative plate of a circular entitled " Fresh-water Sponges," recently issued by Mr. Edward Potts, an active member of the Academy of Natural Sciences of Philadelphia.

To the enthusiastic student there is probably no field of scientific investigation which offers a greater prospect of novelty and interest than the study of the flora and fauna of this country as represented in the microscopic life of its lakes and streams. It is a singular fact that while hundreds of naturalists, amateur and professional, have devoted years to the collection and study of diatoms, the higher algae, the rhizopods and, as we think them; the far more interesting rotifera, polyzoa, etc, hardly any appear to have observed or collected the class of animals described in this article. And yet, occupying fixed positions as there described, and easily recognized by the naked eye, they are far more readily discovered and collected than most of the above-mentioned objects. Simply drying or bottling them in alcohol preserves them for future study; the process of preparation for microscopic investigation is quickly learned, and the forms of their resultant elements, as hinted at in the accompanying plate, are wonderful in their variety and grotesqueness.

It is greatly to be hoped that many of our young people whose scientific instincts lead them to the exploration of the ponds and creeks of their respective neighborhoods, as well as those who haunt our lakes and rivers through the summer season, for the enjoyment they find in boating and bathing, in fishing and shooting along their shores, may be inspired by this article to assist Mr. Potts in the preparation of his intended monograph by forwarding to him specimens of such sponges as his description may have taught them to recognize and appreciate. The season for collecting is at its best; even now (September 1st) the slime-like flesh of some species, already mature, is beginning to decay; their spicules will soon be scattered by the autumn floods, and a few seed-like stato-blasts, the winter eggs of the sponges, will alone remain to show where they once had been.