These worms live in muddy sand and are abundant in many locations at Woods Hole, Mass. The sexes are separate; mature males can be recognized by the bright orange body color which develops during the breeding season (Mead, 1898).

The limits of the season have not been established for the Woods Hole region, but ripe individuals are available during July and at least the early part of August (Bumpus, 1898). Mead (1898) states that the height of the breeding season is early July, and that nearly ripe females were found as early as April 17.

A. Care of Adults: The worms should be washed free of mud and placed in a fingerbowl of sea water. It is best if the water is changed daily.

B. Preparation of Cultures: Spawning occasionally occurs in the laboratory. After it is completed, the adults should be removed and the eggs allowed to remain undisturbed for an hour or so. Then the inseminated eggs should be transferred to a fingerbowl of fresh sea water. Change the sea water daily.

A. The Unfertilized Ovum: The mature ovum measures approximately 104 microns in diameter. It is opaque and pale yellow-green in color. A conspicuous refractive membrane is present. The egg is probably shed in the germinal vesicle stage, but the oöcyte nucleus quickly ruptures and the egg proceeds spontaneously to metaphase of the first maturation division.

B. Cleavage: Although no details of cleavage are available in the literature, it is presumably spiral.

C. Rate of Development: Development is relatively rapid. A trochophore-like form, which never becomes an active swimmer, appears within about 24 hours, but it is rapidly converted into a three-segmented larva. Metamorphosis is well on its way by the fourth day after insemination.

D. Later Stages of Development: The vestigial trochophore has an apical tuft and a poorly developed prototroch. A three-segmented larva is formed.

SPECIAL COMMENTS:

Although this animal was at one time routinely used in the Embryology Course at Woods Hole, practically no details of its culture or embryology are recorded. Since it is quite abundant in the Woods Hole region, it merits further investigation.

BUMPUS, H. C., 1898. The breeding of animals at Woods Holl during the months of June, July and August. Science, 8: 850 858.

MEAD, A. D., 1898. The breeding of animals at Woods Holl during the month of April, 1898. Science, 7: