The adults live in small tubes shaped like ice-cream cones, made of sand grains cemented together. They are found in muddy sand in shallow water, and can be collected readily by digging on sand flats around Woods Hole, Mass. The sexes are separate.

The limits of the season have not been investigated, but it is possible to secure ripe animals at least during August.

A. Care of Adults: These worms are quite hardy and will survive in the laboratory if they are kept in dishes of running sea water, whether they are removed from their tubes or left in them.

B. Procuring Gametes: Eggs and sperm can be obtained by removing male and female animals from the tubes and pinching the bodies with a pair of fine forceps. When first released, the sperm are in packets, but these quickly break up into masses of free-swimming sperm when they come into contact with sea water.

C. Preparation of Cultures: Just (1922) reports that the larvae can be reared through metamorphosis, but without special feeding the trochophores die within a few days.

A. The Unfertilized Ovum: The mature ovum measures approximately 55 microns in diameter. It is pale yellow-green in color and very transparent, showing internal changes without staining. The egg contains a large germinal vesicle with a prominent nucleolus when shed, but the vesicle breaks down rapidly when the egg comes in contact with sea water.

B. Fertilization and Cleavage: A thin membrane is elevated at the time of fertilization. The formation of two polar bodies quickly follows. Cleavage is total, unequal and spiral; the D cell is markedly larger than the other macromeres, and the micromeres are usually large. Gastrulation is by invagination.

C. Time Table of Development: The following table shows the rate of development at 24û C. The time is recorded from insemination.

Stage Polar bodies formed Fusion of pronuclei First cleavage Second cleavage	Time 29 minutes 40 minutes 54 minutes 72 minutes
Stage Third cleavage Free-swimming blastula Gastrula Well-formed trochophore	Time 92 minutes 5 hours 10 hours 22 hours

D. Later Stages of Development: The trochophore is small and transparent. It has a long tuft of apical cilia and a well-developed prototroch. Ciliated lateral and anterior lips overhang the mouth like a hood. From one of the lower corners of the mouth a tuft of long cilia protrudes; it is particularly noticeable in side view. There are indications of a telotroch. The tri-partite digestive tract is well ciliated and contractile. The diagrams by Wilson (1936), illustrating the larvae of a European species of Pectinaria, show that these larvae are almost identical with those of Cistenides gouldi.

JUST, E. E., 1922. On rearing sexually mature Platynereis megalops from eggs. Amer. Nat., 56: 471-478.

WILSON, D. P., 1936. Notes on the early stages of two polychaetes, Nephthys hombergi Lamarck and Pectinaria koreni Malmgren. J. Mar. Biol. Assoc., 21: 305-310.