[16] I draw this conclusion from Gegenbaur's fig. (No. 10), Pl. XVI., fig. 15. The body (_x_) in the figure appears to me without doubt the rudiment of the stolon, and not, as believed by Gegenbaur, the larval tail. On this stolon there develop two entirely different types of buds, (1) lateral buds, (2) dorsal median buds. The lateral buds are developed in regular order on the two sides of the stolon, and the most advanced buds are those furthest removed from the base. They give rise to forms with a very different organization to that of the parent. They are compared by Gegenbaur to a spoon, the bowl of which is formed by the branchial sack, and the handle by the stalk attaching the bud to the stolon. The oral opening into the branchial sack is directed upwards: _an atrial opening is remarkably enough not present_. The branchial sack is perforated by numerous openings. It leads into an alimentary tract which opens directly to the exterior by an anus opposite the mouth. The stalks attaching the more mature buds to the stolon are provided with ventrally directed scales, which completely hide the stolon in a view from the ventral surface. These buds have, even after their detachment, no trace of generative organs, and shew no signs of reproducing themselves by budding. Their eventual fate is unknown. The median dorsal buds have no such regular arrangement as the lateral buds, but arise in irregular bunches, those furthest removed from the base of the stolon being however the oldest. These buds are almost exactly similar to the original sexual form; they do not acquire sexual organs, but are provided with a stolon attached on the ventral side, in the sixth intermuscular space. This stolon is simply the stalk by which each median bud was primitively attached to the stolon of the first asexual form. From the stolon of the median buds of the second generation buds are developed which grow into the sexual forms. The generations of Doliolum may be tabulated in the following way. Sexual generation, | 1st asexual form with dorsal stolon, _________________|_____________________ | | spoon-like forms developed as 2nd asexual forms developed as lateral buds (eventual history median buds with ventral stolon, unknown). | sexual generation. BIBLIOGRAPHY. (6) P. J. van Beneden. "Recherches s. l'Embryogénie, l'Anat. et la Physiol. des Ascidies simples." _Mém. Acad. Roy. de Belgique_, Tom. XX. (7) W. K. Brooks. "On the development of Salpa." _Bull. of the Museum of Comp. Anat. at Harvard College, Cambridge, Mass._ (8) H. Fol. _Etudes sur les Appendiculaires du détroit de Messine_. Genève et Bâle, 1872.