The adults are common on sea-weed at Nobska Beach.

This has not been investigated in the Woods Hole, Mass., area. In European waters, the animals breed from January until June.

A. Care of Adults: Breeding adults can be maintained in laboratory aquaria. They should be supplied with Fucus or other sea-weed, for, as noted above, it is on these plants that the eggs are usually deposited.

B. Obtaining Gametes: The eggs are deposited in a clear, gelatinous capsule, which is covered by a thin, lens-shaped panicle. The egg-mass is in the form of a ring which is often oval in outline. Although it measures only about 3 mm. across when freshly laid, it swells enormously during the course of development. Photographs of the egg-mass are available in the paper by Hertling and Ankel (1927).

NORMAL DEVELOPMENT

A. Egg Characteristics: The eggs are golden, cream or greenish in color, and measurements of their diameter range from 103 to 180 microns (Lebour, 1937; Hertling and Ankel, 1927). Each egg is surrounded by an inner membrane and an outer capsule which swells as development proceeds. The number of eggs in each mass is large, varying between 1000 and 1200. They are sensitive to rising temperature, but apparently can withstand quite rigorous experimental treatment (Herding, 1928).

B. Cleavage and Gastrulation: Cleavage is total, equal and of a typical spiral nature. Information concerning the nature of gastrulation is apparently not available.

C. Rate of Development: Development is slow, but fluctuates widely with the temperature. Hertling (1928) states that by the thirteenth day, the velum is visible. By the fifteenth day, the larvae are showing lively movements, and by the seventeenth day, the shell anlage appears. Hatching occurs on the twenty-sixth day. The exact temperature for the above developmental schedule is not given, but it is presumed to be slightly below 20• C.

D. Later Stages of Development: Lebour (1937) describes the newly-hatched veliger as having well-formed eyes, otocysts, foot, and operculum. The mouth is open. The shell consists of 1-1/2 whorls, and is clear, colorless, and lacking in sculpturing. The velum has long cilia, and is marked by a brownish-red border. For diagrams of the larva, consult the papers of Lebour (1937) and Hertling (1928).

HERTLING, H., 1928. Beobachtungen und Versuche an den Eiern von Littorina und Lacuna. Wiss. Meeres. Komm. Unt. Deutsch. Meere, N. F., Abt. Helgoland, 17 (2): 1-49.

HERTLING, H., AND W. E. ANKEL, 1927. Bemerkungen über Laich und Jugendformen von Littorina und Lacuna. Wiss. Meeres. Komm. Unt. Deutsch. Meere, N. F., Abt. Helgoland,

LEBOUR, M. V., 1937. The eggs and larvae of the British prosobranchs with special reference to those living in the plankton. J. Mar. Biol. Assoc., 22: 105-166.