Although the changes which take place during budding do not fall within the province of this work, it may be well to state that Hatschek has observed during this process the development of the nervous system and the generative organs. The nervous system arises as an unpaired thickening of the epiblastic floor of the vestibule, between the mouth and the anus. On becoming constricted off from the epiblast the nerve ganglion contains a central cavity which afterwards vanishes. The generative organs originate as a pair of specially large mesoblast cells in the space between the stomach and the floor of the vestibule. These two cells, surrounded by an investment of flattened mesoblast cells, subsequently divide and form two masses. At a still later period each mass divides into an anterior and a posterior part; the former giving rise to the ovary, the latter to the testis. The similarity of this mode of development of the generative organs to that observed by Bütschli in Sagitta, which is described in the sequel, is very striking. ECTOPROCTA. Although the embryology of the Ectoprocta has been investigated by a very considerable number of the distinguished naturalists of the century, many points connected with it still stand in great need of further elucidation. The original nature of the embryo was rightly interpreted by Grant, Dalyell and other naturalists, but it was not till Huxley demonstrated the presence of both the ovary and testis that the true sexual origin of the embryo in the ovicells became an established fact in science. The recent memoir of Barrois (No. 298), though it contains the record of a vast amount of research, and marks a great advance in our knowledge, still leaves a great number of points, both with reference to the early development and to the larval metamorphosis in a very unsatisfactory condition. Four larval forms can be distinguished, viz. (1) A larval form which with slight modifications is common to all the genera of the Chilostomata (except Membranipora and Flustrella) and of the Ctenostomata. (2) A bivalved larva of Membranipora known as _Cyphonautes_, the true nature of which was first recognized by Schneider (No. 322), and the closely allied larva of Flustrella. (3) The typical Cyclostomatous larva, for the first full description of which we are indebted to Barrois (No. 298). (4) The larva of the Phylactolæmata.