considerable advance in this direction only at the cost of tenacious patience and untiring industry. His subsequent labors on the _Rhabdocoelas_ of the vicinity of Cracow, the _Dendrocoelas_ of the vicinity of Grätz, and his researches on the _Turbellaria_ of Corfu and Cephalonia, which (in 1861) closed this period of his career as worthily as it had begun, proved that Schmidt possessed both these requirements. These labors, if he had accomplished no more, would have been sufficient to give him an honorable position in science for all time. "The second period begins in Grätz. Some contributions to the knowledge of the prehistoric vertebrate fauna of Steiermarck resulted from Schmidt's keen observations of Nature during an excursion in the Alps. But the Adriatic, so near, enticed him into new paths, and offered an inexhaustible field for work in the sponges. Aside from his contributions to the theory of the _Bathybius_ and to the systematics of the _Gephyrea_, the sea sponges constituted the object of his studies during the whole period of his residence in Grätz, and were the occasion of yearly journeys to the Adriatic coasts. The results reached by Schmidt in this field placed him in the foremost rank of contemporary investigators, while his occupation with the sponges marked the completion of a revolution in his view of Nature by converting him to Darwinism. After his work the characteristic fluid form of the sponges became a classic subject in the study of the transmutation theory.