The ECHINUS is said to be essentially herbivorous, but my cursory observation leads me to the opinion (very humbly proffered) that it fulfils a definite purpose in the order of Nature, too, and depends for sustenance, or for the building up of its structure, upon certain constituents of the coral. Does it not break and grind down to powder the ramparts of coral? Clumsy and ill-shaped as it appears to be in other respects, it has jaws of wonderful design, and known to the ancients as "Aristotle's lantern." They are composed of five strips of bony substance, with enamel-like tips overlying each other in the centre of the disc-shaped mouth. With this splendid instrument the creature grips and breaks off or gnaws off, or bores out crumbs of coral which you find, apparently in process of digestion, as you render him an acceptable morsel. Scientific observers affirm that by means of an acid which the ECHINUS secretes, it disintegrates the rock, and that the jaws are used merely to clear away the softened rubbish. How is it then that the globular cavity is often well-ballasted with tiny crisp chunks of coral rock? Possibly to the assimilation of the lime is due, in some measure, the singularly sweet and expressive savour. So we see the coral-reef-building polyps toiling with but little rest, almost incessantly labouring to raise architectural devices of infinite design, and other creatures as industriously tearing them down to form the solid foundation of continents. Another species of ECHINUS eludes its enemies by the adoption of a cumbersome and forbidding mask. Ineffectively armed, the spines though numerous being short and frail, it holds empty bivalve shells on its uppermost part, The unstudied accumulation of debris--a fair sample of the surrounding ocean floor--would fail to fix notice, but that it moves bodily and without apparent cause. Inspection penetrates the disguise. Wheresoever the ECHINUS goes--its progress is infinitely slow--it carries a self-imposed burden--the refuse of dead and inanimate things--that it may, by imposition upon its foes, continue in the way of life. SHARKS AND SKIPPERS