This quick-footed sand-digger enhances its reputation by the performance of feats of subtlety and skill. Its bolt-hole is sometimes three feet deep, generally on an incline. Piled in a mound the spoil would inevitably betray the site of the operations to the policeman, thus seriously facilitating the duties of that official towards the suppression of the species. From remote depths the crab carries a bundle of sand. You remember the trenchant way in which Pip's sister cut the bread and butter, her left hand jamming the loaf hard and fast against her bib? Just so the crab with its bundle of loose sand, though it has the advantage in the number of limbs which may be pressed into service. The feat of carrying an armful of sliding sand in proportion to bulk about one-third of the body, is far away and beyond the capacities of human beings, but to the crab, which has acquired the trick of temporary consolidation by pressure, it is merely child's play. Arrived at the mouth of the shaft, it elevates its eyes (which in the dark have rested in neatly fitting recesses) for the purpose of a cautious yet sweeping survey. Seeing nothing alarming, it emerges with the alertness of a jack-in-the-box, races several inches, and scatters the load broadcast as the sower of seed who went forth to sow. Then, as suddenly, the crab pauses and flattens itself--its body merging with its surroundings almost to invisibility--preparatory for a spurt for home. During these exertions the intellect of the crab has been concentrated for outwitting the vigilance of enemies, for the plodding policeman is not singular in appreciation. The lordly red-backed sea-eagle occasionally condescends to such humble fare, and the crab must needs be alert to evade the scrutiny with which the eagle searches the sand. This passing reference to the wit and deftness of the crab would be quite uncomplimentary in default of special notice of the plug of sand with which it stops its burrow. As a rule it is about an inch thick, and in content far more than a crab could carry in a single load. How does the creature, working from below and with such refractory material, so arrange that the plug shall be flush with the surface and sufficiently consolidated to retain its own weight? Of what art in loose masonry has the crab the unique secret? Shakespeare speaks of stairs of sand, and Poe laments the "how few" grains of golden sand which crept through his fingers to the deep; but who but a crab possesses the secret for the building of a roof of the material which is the popular emblem of instability and shiftiness? The impartial student must not restrict his notions as to the possibilities of sand to the admirable accomplishments of crabs. He may also inspect with profit the handicraft of a lowly mollusc which agglutinates sand-grains into a kind of plaque, in the substance of which numerous eggs are deposited.