The goose barnacle is not indigenous to the Woods Hole, Mass., region; however, during the summer, timbers and wooden boxes with barnacles attached may sometimes drift into the harbor from the Gulf Stream.

The limits of the season are not known. Bigelow (1902) states that he found maturation stages early in June, whereas by July and August, young nauplii were prevalent.

A. Care of Adults: Sections of timbers with adherent barnacles may be placed in aquaria supplied with running sea water, in the laboratory, or larger timbers may be anchored in the Eel Pond. Detached animals will also live in an aquarium in the laboratory.

B. Procuring Gametes and Embryos: Lepas is hermaphroditic and can fertilize its own gametes; these embryos are then deposited in the mantle cavity in sheet-like ovigerous lamellae, where they continue to develop until they hatch as nauplii. If one wishes to examine the gametes, they can be procured by slitting a barnacle along the plate hinges and exposing the visceral mass. The testes lie at the stalk side of the body, and when the animal is in a breeding condition, they are white and swollen. The ovary is found by cutting the stalk lengthwise; young egg-masses are bright blue. In this condition, unfertilized eggs can be found; it has not been ascertained whether such eggs can be artificially inseminated. For cleavage stages, it is better to study the eggs which are obtained from the ovigerous lamellae.

If enough animals are available, a complete series, from egg to hatching larva, may be obtained at the same time. During development, there is a striking color change in the eggs of the lamellae: early cleavage stages are medium blue, later cleavage stages are light blue to blue-lavender. In pink-lavender lamellae, larvae can be seen inside the egg cases. Hatching stages are pink in color, while young to mature swimming nauplii accumulate in peach-colored masses. The chemistry of this color change has been studied by Ball (1944).

The lamellae lie as two sheets which are at first closely applied to the lower portion of the visceral mass and later are extended to cover the entire inside of the mantle cavity. When the lamellae are old enough to contain hatching stages, they are extruded from the body when the tentacles are molted. The bottom of the aquarium should therefore be inspected for these peach-colored sheets, which are about thumb-nail size.

The various stages may be isolated in separate fingerbowls. Bigelow (1902) states that the early embryos will not continue development outside the broodchamber for a period of longer than five to ten hours. Late nauplii, however, will live for some time in fingerbowls of sea water.

C. Methods of Observation: To aid in the study of cleavage stages, it is helpful to stain with strong methyl green; the micromeres stain deeply, the macromeres, faintly. The stain, however, is transient.

A. The Unfertilized Ovum: The eggs are distorted while they are still in the ovary, but become spherical in shape after they are placed in sea water. According to Bigelow (1902) the first polar body is given off when the eggs leave the oviducts; whether or not fertilization occurs at this time, the vitelline membrane is elevated and lies, therefore, between the egg surface and the first polar body.

B. Fertilization and Cleavage: After fertilization, waves of slow contraction can be seen in the egg; Groom (1894) states that this process separates the protoplasmic portions of the egg from the yolk. The egg has a rounded point at the vegetal pole and is blunt at the animal pole. Cleavage is total, unequal, and regular. For a complete account of cleavage and of the cell lineage of this form, see the paper by Bigelow (1902).

Costello (1948) has pointed out that the cleavage of Lepas can be homologized with that of spirally cleaving eggs by considering it to be cleavage by "monets" rather than by quartets.

C. Later Stages of Development and Metamorphosis: Groom (1894) gives an account of later development (as well as maturation and early cleavage stages). The papers of Bigelow (1902) and Groom (1894) contain illustrations of stages from the unfertilized ovum to the early unhatched larva. Groom continues the series to the mature nauplius larva.

BALL, E. G., 1944. A blue chromoprotein found in the eggs of the goose-bamacle. J. Biol. Chem., 152: 627-634.

BIGELOW, M. A., 1902. The early development of Lepas. A study of cell-lineage and germ layers. Bull. Mus. Comp. Zool., Harvard, 40: 61-144.

COSTELLO, D. P., 1948. Spiral cleavage. Biol. Bull., 95: 265. (See, also, Erratum, Biol Bull., 95: 361.)

GROOM, T. T., 1894. On the early development of Cirripedia. Phil. Trans. Roy. Soc., London, ser. B, 185: 119-232.