Darwin gives an interesting description of these extraordinary animals: “I have before alluded to a crab which lives on cocoanuts; it is very common on all parts of the dry land, and grows to a monstrous size. The front pair of legs terminate in very strong and heavy pincers, and the last pair are fitted with others weaker and much narrower. It would at first be thought quite impossible for a crab to open a strong cocoanut covered with husk, but Mr. Liesk assures me that he has repeatedly seen this effected. The crab begins by tearing the husk, fiber by fiber, and always from that end under which the three eye-holes are situated. When this is completed, the crab commences hammering with its heavy claws on one of the eye-holes till an opening is made. Then turning round its body, it extracts the white albuminous substance with its posterior and narrow pair of pincers. “Every night it is said to pay a visit to the sea, no doubt for the purpose of moistening its gills. The young are likewise hatched, and live for some time, on the coast. These crabs inhabit deep burrows, which they hollow out beneath the roots of trees, and there they accumulate surprising quantities of the picked fibers of the cocoanut husk, on which they rest as a bed. To show the wonderful strength of the front pair of pincers, I may mention that Captain Moresby confined one in a strong tin box, the lid being secured with wire; but the crab turned down the edges and escaped. In turning down the edges, it actually punched many small holes through the tin!” How are Files Made? A good tool-kit holds a number of files of various shapes. Some are flat, others half-round, three-sided, square and round. They are generally thickest in the middle, while their teeth are of various degrees of fineness and of different forms. A file whose teeth are in parallel ridges only is called single-cut or float-cut. Such are mostly used for brass and copper. When there are two series of ridges crossing each other the file is double-cut, which is the file best suited for iron and steel. Rasps are files which have isolated sharp teeth separated by comparatively wide spaces, and are chiefly used for soft materials such as wood and horn. Each of these three classes of files is made in six different degrees of fineness, the coarsest being called rough, the next middle, followed by bastard, second-cut, smooth and superfine or dead-smooth, each a degree finer than that which precedes it. Files are usually made with the hand, file-cutting machines not having been as yet perfectly successful on account of the delicacy of touch required in the work.