For the last few days I have been especially occupied with the development of the medusae. In studying the actiniae I have made a striking discovery, and I should be glad if you would communicate it to the Academy in advance of the illustrated paper on the same subject, which I hope soon to send you. Notwithstanding their star-like appearance, the star-fishes have, like the sea-urchins, indications by no means doubtful, of a symmetrical disposition of their organs in pairs, and an anterior and posterior extremity easily recognized by the special form of their oral opening. I have now satisfied myself that the madrepores have something analogous to this in the arrangement of their partitions, so that I am tempted to believe that this tendency to a symmetrical arrangement of parts in pairs, is a general character of polyps, disguised by their radiating form. Among the medusae something similar exists in the disposition of the marginal appendages and the ocelli. I attach the more importance to these observations, because they may lead to a clearer perception than we have yet reached of the natural relations between the radiates and the other great types of the animal kingdom. This summer I hope to explore the lower lakes of Canada, and also the regions lying to the eastward as far as Nova Scotia; in the autumn I shall resume my excursions on the coast and in the Alleghenies, and shall pass a part of the winter in the Carolinas. I will soon write to Monsieur Brongniart concerning my plans for next year. If the Museum were desirous to aid me in my undertakings, I should like to make a journey of exploration next summer in a zone thus far completely neglected by naturalists, the region, namely, of the small lakes to the west of Lake Superior, where the Mississippi takes its rise, and also of that lying between this great basin of fresh water and the southern arm of Hudson Bay. I would employ the autumn in exploring the great valley of the Mississippi, and would pass the winter on the borders of the Gulf of Mexico. To carry out such projects, however, I have need of larger resources than I can create by my own efforts, and I shall soon be at the end of the subsidy granted me by the King of Prussia. I shall, however, subordinate all these projects to the possibilities of which you kindly tell me. Notwithstanding the interest offered by the exploration of a country so rich as this, notwithstanding the gratifying welcome I have received here, I feel, after all, that nowhere can one work better than in our old Europe, and the friendship you have shown me is a more than sufficient motive, impelling me to return as soon as possible to Paris. Remember me to our common friends. I have made some sufficiently interesting collections which I shall forward to the Museum; they will show you that I have done my best to fulfill my promises, forgetting no one. . .