Imperfections in the texture and luster of the skin are said to be due to the movement of the growing pearl among the zones of the mollusk's mantle supplying the varied material for the epidermis, middle shell, and lining. The difficulties confronting this theory are explained in the chapter on the "Genesis of Pearls." These imperfections consist generally of dead white chalky spots and streaks, distributed over the surface of the pearl, oftentimes so small as to escape notice except under the loup. Sometimes these imperfections take the form of rings or bands which encircle the pearl. Pearls so marked are rarely if ever round, but ovoid, capsule, or cartridge shaped, and these chalky lines always encircle the cylinder; they never cross the dome. Rings around the dome occur, but the surface over them is of equal luster. Frequently the entire outer skin is without luster. Whether this arises from lack of some element in the exudations of the mollusk from which the pearl is created, or from an imperfect crystallization of the calcium carbonate, is not known. Such skins have the usual nacreous surface wave lines and are often lustrous immediately under the outer plates of the skin. It is possible that these chalky skins may result from the extraction of the pearl from the mollusk during a transitional stage, and that the presence of spots and streaks of that character, scattered over an otherwise lustrous surface, indicates that the secretions of the creature's mantle did not hold some essential ingredient in sufficient quantity to secure perfect crystallization and thereby cover the entire surface with transparent plates of calcium carbonate. It may be also that a lack of essential elements in the creature's exudations, causes a cessation of the mantle's action which by all signs appears necessary for the production of transparent plates of nacre. "Peelers" are pearls of imperfect skins having indications of a better one underneath. Speculators buy these pearls at a low price and skin them. Sometimes they are rewarded by a smaller, but much more valuable pearl. Many times the under skins are no better or worse, or if better, the loss in size and weight, together with the cost of the work, make it unprofitable. Peeling should not be attempted with cylindrical shaped pearls having chalky bands or rings around them, as such imperfections usually penetrate to the interior in pearls of that character. Cylindrical pearls are almost invariably fresh-waters. The imperfections disclosed in the under skins by peeling, are commonly irregularities of shape which have been rounded over to the improvement of the sphericity of the pearl.