It revealed living coral, good to avoid by the barefooted; clams with patterned mantles of various tints--grey, slate-blue, sea-green, brown, and buff; anemones in many shapes, some like spikes of lavender, and irritant and repellent to the touch; some platter-shaped and cobalt-blue; some as living vases with the opalescent tints of Venetian glass, which, abhorring the hand of man, retreat into the sand until only an inconspicuous fringe of neutral tint is visible. Sea-slugs in almost endless form and variety of hue, and many other strange sea things, were among the inhabitants of the reef--a closely packed arena of never-ceasing slaughter. In the middle of a clump of brown seaweed, which had fallen apart like the neatly dressed hair of a woman, was a black streak, signifying the gape of a wedge-shaped mollusc known as a pinna. The gape was about as long as the parting of a woman's hair and about thrice as wide. As I crouched to note the functions of the animal, my shadow intervened and the caution of the creature was roused, the valves closing so that no sign of the presence of the shell was distinguishable among the slightly wavering, minute particles of alga. Changing my position, so that the pinna might not be deprived of its share of the rays of the sun, the valves soon furtively opened. A slight movement on my part and they closed again, without having revealed any hidden charms. After a few minutes, a certain confidence being established between us, the pinna emerged from its retirement, in so far as such creatures are permitted by Nature. The mantle of this particular species is shown as a delicate fringe of lace in old gold and black. It ripples along the upper edges of the confining valves, which are intensely black with a pearly lustre. The pretty movements of the mantle--like the swinging of the skirts of a well-apparelled damsel--attracted admiration, and on peering into the shell a glimpse of something precious was obtained. Tossed and twirled about just below the old gold fringe was a black pearl about the size of a pea. The prize was safe. Without risk of loss it could be watched in its unceasing revolutions. It seemed as if the animal, with automatic perseverance, attempted to eject the incubus, the weight of which kept it about an inch below the aperture of the valves. Such motion would naturally tend to perfection. Whatsoever its lustre, it would certainly be a sphere. Besides, it was a pearl in the making. As long as it remained within the pinna and it could not be voluntarily rejected, its size would inevitably increase. It was the rolling stone to which time and the secretions of the animal would add weight and, peradventure, beauty.