Development of Scolecolepis fuliginosa (Claparède)

Abstract

1. The development of Scolecolepis fuliginosa (Claparède) is described from the egg to the young worm for the first time.2. Comparison of reared larvæ with larvse from the plankton did not reveal any important difference.3. The eggs are pelagic, and are similar to those of Nerine.4. A description is given of the histological structure of a ciliated pit which arises in early larval existence and disappears at metamorphosis. The structure of the glandular region of the pygidium is also described.5. It is apparent that from the attainment of the fourth setiger onwards, the centre of differentiation is located in the third setiger, so that segmental structures arise first in this segment and then appear in the first and second setigers as well as in the succeeding ones.6. The larva of Scolecolepis has three pairs of eyes, the third pair disappearing in the young worm long after metamorphosis is otherwise complete.