association with a number of like-minded co-workers, all striving toward the same end. With every year, however, the number of able and influential investigators increases here, and among them are some who might justly claim a prominent place anywhere. . . Neither are means for publication lacking. The larger treatises with costly illustrations appear in the Smithsonian Contributions, in the Transactions of the American Philosophical Society, in those of the Academy of Natural Sciences, and in the Memoirs of the American Academy; while the smaller communications find a place in Silliman's Journal, in the Journal of the Boston Natural History Society, and in the proceedings of other scientific societies. Museums also are already founded;. . .and beside these there are a number of private collections in single departments of zoology. . . Better than all this, however, is the lively and general interest taken in the exploration of the country itself. Every scientific expedition sent out by the government to the interior, or to the Western States of Oregon and California, is accompanied by a scientific commission,--zoologists, geologists, and botanists. By this means magnificent collections, awaiting only able investigators to work them up, have been brought together. Indeed, I do not believe that as many new things are accumulated anywhere as just here, and it is my hope to contribute hereafter to the more critical and careful examination of these treasures. Under these circumstances I have asked myself for months past how I ought to decide; not what were my inclinations, for that is not the question,--but what was my duty toward science? After the most careful consideration I am no longer in doubt, and though it grieves me to do so, I write to beg that you will withdraw from any action which might bring me a direct call to the professorship in Zurich. I have decided to remain here for an indefinite time, under the conviction that I shall exert a more advantageous and more extensive influence on the progress of science in this country than in Europe. I regret that I cannot accept your offer of the Oeningen fossils. In the last two years I have spent more than 20,000 francs on my collection, and must not incur any farther expense of that kind at present. As soon, however, as I have new means at my command such a collection would be most welcome, and should it remain in your hands I may be very glad to take it. Neither can I make any exchange of duplicates just now, as I have not yet been able to sort my collections and set aside the specimens which may be considered only as materials for exchange. Can you procure for me Glarus fishes in any considerable number? I should like to purchase them for my collection, and do not care for single specimens of every species, but would prefer whole suites that I may revise my former identifications in the light of a larger insight.