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262 and in connection with the Boston Society is manager of the Teachers' School of Science, which was founded in 1870-'71, for the purpose of giving lectures to teachers in Boston and vicinity.

The Society of Naturalists of Eastern United States, founded in 1883, really arose from an idea of Professor Hyatt's that there should be a society representing the practical side of natural history. lie communicated his ideas to Professor Clark, of Williams College, who realized the value of the plan; and it was mainly through the executive ability and energy of Professor Clark that the first meeting was called at Springfield. Professor Hyatt was elected first president of the society for a term of two years. In 1869 he was elected Fellow of the American Academy of Arts and Sciences, and in 1875 he became Fellow of the National Academy.

In his scientific researches Professor Hyatt has been exceedingly active. He first published an article upon "Beatrecia," a large and curious fossil first described as a tree, and then successively placed by different authors in all the several classes of Invertebrata, till at last, by another paper of Professor Hyatt's, it has been again shifted to the Protozoa. In 1866 appeared his "Observations on Polyzoa," an article of importance at that time, upon the structure of this curious and beautiful group of fresh-water animals. This was followed, in 1867, by an article upon "Parallelism between Different Stages of Life in Tetrabranchiata," and in 1872 by an important paper upon the "Fossil Cephalopods of the Museum of Comparative Zoölogy." In these and other subsequent pamphlets upon the fossil cephalopods he has steadily endeavored to elaborate a practical demonstration of the theory of evolution, and to illustrate the laws by which this has taken place among the cephalopods. One of his best works is "Revision of North American Poriferæ," the only work on North American commercial sponges, and one which is recognized throughout the world as one of the finest monographs of Porifera ever published. The field was entirely unexplored, and the group one of the hardest in the animal kingdom—so hard, in fact, that few naturalists have ever touched it. In his "Effects of Gravity upon Forms of the Shells of Planorbis," Professor Hyatt shows how important the action of gravity has been in modifying the shape of the shells of Ammonites and other animals, pointing out many cases where it has undoubtedly fundamentally affected the forms of shells and the growth of the parts and organs of the animals, and produced specific and generic modifications. Some of Professor Hyatt's most important theories have been set forth in an extensive paper, entitled "Genesis of Tertiary Species of Planorbis at Steinheim." It covers one hundred pages, quarto, and has nine plates. Professor Hyatt went to Steinheim with the intention of making additional observations and proving Hilgendorf's theory of the evolution of Planorbis, which was then recognized by paleontologists in Europe as the only positive demonstration of the theory of evolution.