These animals are relatively abundant at Woods Hole, Mass. They may be obtained during the day from the bottom or vegetation of Eel Pond, or during the evening, between 7:30 and 9:30, when the mature worms are swarming at the surface. They are attracted by the light of the Nereis-collecting lamps. The sexes are separate, and when the animals are ripe, they may be distinguished by the color of the gametes seen through the semi-transparent body wall; the females are seal-brown, the males cream color.

A. Care of Adults: Transferred to clean dishes, with an occasional change of sea water, these worms will live indefinitely in the laboratory. It is best to segregate the sexes.

B. Procuring Gametes: Swarming animals usually will shed when taken. Females procured during the day shed eggs from 7:30 to 9 P.M. on the second or third, but rarely on the first, night after collection (Treadwell, 1901). The eggs sink to the bottom of the dish where they may be collected with a pipette. A simpler method of collecting them is to strain the water through a fine cloth which allows the eggs to pass through, but retains the spent adults.

C. Preparation of Cultures: Fertilized eggs may be obtained either by placing several males and females in a fingerbowl and allowing them to shed, or by inseminating naturally-shed eggs from isolated females with sperm from the body cavity of the males (Treadwell, 1901).

A. The Unfertilized Ovum The eggs are slightly irregular when first shed, but soon become spherical. The average diameter is about 63 microns, and a thin, smooth membrane is present. Upon shedding, the egg proceeds spontaneously to the metaphase of the first maturation division and remains in this condition until fertilized (Treadwell, 1901).

B. Fertilization and Cleavage: There is no visible alteration of the egg membrane at fertilization. Cleavage is equal and spiral with especially large entomeres; no polar lobes are formed. Gastrulation is by invagination (Treadwell, 1898, 1901 ).

C. Rate of Development: Swimming forms appear five hours after insemination; well-formed trochophores are present in cultures 24 hours old.

D. Later Stages of Development: The trochophores are small, thin-walled and active. They have a large enteron; the intestinal portion of it seems to be almost severed from the remainder by a circular "shelf" of tissue. There is no paratroch, but the neurotroch, prototroch, apical tuft, and an additional anterior tuft are well developed. Two ventral eyespots and five frontal bodies are present (Treadwell, 1899). (See Figure 12 in the paper of Treadwell, 1899, and Figure 60 of Treadwell, 1901.)

JUST, E. E., 1939. Basic Methods for Experiments on Eggs of Marine Animals. P. Blakiston's Son & Co., Inc., Philadelphia.

TREADWELL, A. L., 1898. The cell lineage of Podarke obscura. Preliminary communication. Zool. Bull., 1: 195-203.

TREADWELL, A. L., 1899. Equal and unequal cleavage in annelids. Biol. Lectures M. B. L., Wood's Holl, Mass., 1898, pp. 93-111.

TREADWELL, A. L., 1901. The cytogeny of Podarke obscura Verrill. J. Morph., 17: 399-486.

TREADWELL, A. L., 1902. Notes on the nature of "artificial parthenogenesis" in the egg of Podarke obscura. Biol. Bull., 3: 235-240.