In this communication the author gave the results of some careful observations and dissections he had made of a species of Beröe (Idyia), obtained in abundance during the last summer in the Firth of Forth.

In the anatomy of the adult animal, several points were described which seem to have been hitherto either overlooked or imperfectly examined. In the digestive system, the author noticed the presence of two richly ciliated membranous semi-elliptical flaps, which just before the stomach terminates in the narrow neck which leads into the bifurcating funnel, spring from its walls, and extend, by their free extremities, into the neck and commencement of the funnel.