The development of eggs and nauplii was studied over 19 days. At 1.5°C nauplii hatched after 5 days. Abdominal spines changed their appearance successively during nauplius development, but no moulting was observed in the course of naupliar development. Moulting occurred between the nauplius and the metanauplius stage 13 days after spawning. Swimming activity was weak in the nauplius, while it was vigorous in the metanauplius. A model is presented for the depth distribution of eggs and larval stages. It is also suggested that present collection techniques may inadequately sample eggs and nauplii based on experiments that show that eggs are extremely sensitive to sieving. © 1984 Springer-Verlag.