The Larval Stages of Notomastus latericeus Sars

Abstract

1. Artificial fertilisations of Notomastus latericeus Sars were made and the larvae reared. 2. The two-day old trochosphere is provided with a large central mass of yolk. It has a broad prototroch, a telotroch, a neurotroch and an apical tuft. It swims rapidly. 3. Development consists in the appearance of trunk segments; The most anterior of these is the achaetous peristomium. Those following acquire neuro- and notopodial chaetae. 4. At an age of about ten days the cilia are gradually lost. The larva then has about five chaetigerous segments, the first three bearing bristles, the last two hooded hooks. 5. The young worms lived for some twelve days after metamorphosis and by that time had seven claetigerous segments. Only a little of the yolk still remained. The worms possessed a protrusible introvert and were feeding on diatoms. 6. The larva apart from its strong prototroch and rapidity of swimming does not exhibit any special structural adaptations to pelagic life, such as are found in some other Polychaete larvae. In comparison with Capitella it has fewer segments when it metamorphoses.