These animals are relatively abundant, and can be found in pile scrapings and under stones at the tide level. The sexes are separate; the males are whitish and the females dark on the ventral surface (Mead, 1897; Bumpus, 1898).

From the last of April to nearly the beginning of June (Mead, 1897; Bumpus, 1898).

A. Care of Adults: Males and females should be segregated in individual fingerbowls when brought into the laboratory, and supplied with running sea water.

B. Procuring Gametes: The animals shed during the evening of the day of collection, usually between 8 and 10 o'clock, although sometimes earlier. The shedding of eggs may be induced during this time by plunging the female into a dish of colder water and then placing the dish close to a lamp. The eggs can stand for several hours in sea water before insemination without impairing normal development (Mead, 1897).

Normal DEVELOPMENT

A. The Unfertilized Ovum: The egg is irregular in shape when first shed, but soon becomes spherical. It measures 65 microns in diameter, and is rather opaque, although it contains a relatively small amount of yolk. A smooth, thin, closely fitting membrane is present.

B. Fertilization and Cleavage: There is apparently no information as to the time of sperm entrance. Cleavage is equal and spiral; no polar lobes are formed. Gastrulation is by invagination (Mead, 1897).

C. Rate of Development: In general, development proceeds rather slowly. Swimming forms are present 8 to 10 hours after insemination; gastrulation occurs in about 20 hours, well-formed trochophores by 48 hours. After this, there is little change for several days. The rate of development, however, is greatly increased with a rise in temperature (Mead, 1897).

D. Later Stages in Development: During the gastrula stage the trochophore assumes a remarkable shape: the membrane stands out from the body except in the regions of the apical tuft and the wide prototroch. The older trochophores are thin-walled and have a narrow, well-developed prototroch with longer cilia, and a neurotroch. An eyespot is present. (See text figures 19 and 20, and plate figure 104 in the paper by Mead, 1897.) The larvae show several interesting reversals of phototropic response during development according to Mead (1897).

BUMPUS, H. C., 1898. The breeding of animals at Woods Holl during the month of May, 1898. Science, 8: 58-61

MEAD, A. D., 1894. Preliminary account of the cell lineage of Amphitrite and other annelids. J. Morph., 9: 465-473.

MEAD, A. D., 1897. The early development of marine annelids. J. Morph., 13: 227-326.

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