Few pearls are perfect. The great majority of small pearls even, fail in one or more of the ideal qualities, and as the size increases perfection becomes more rare. A perfect pearl is not necessarily of the finest luster, but it must be lustrous and of even luster all over. If round, it must be spherically round; if pear or ovoid, symmetrically so, and the skin must be free from blemishes. Baroque and button pearls are naturally imperfect pearls, the former being fantastically irregular in shape and the latter partially deformed. Imperfections of shape in what are termed round pearls are more numerous than those unaccustomed to handling them would suppose. A lot of pearls which to the casual glance seem to be all quite round, will be found often on close examination to contain many, if not a majority, that are not. Upon rolling them separately, irregularities will appear which the luster and contiguity of others concealed. It will be discovered that the domes of some are slightly flattened at one part of the sphere; in others at two opposite points so as to form a double domed disk. Very many have slight protuberances above the contour of the sphere, or places in the spherical line, which though not flat, are depressed. While these minor imperfections of shape do not materially hurt the beauty of the pearl, they do decrease the value somewhat, and as they are quite common even among fine selected pearls they accentuate the rarity of the perfectly spherical. The adventures of a pearl from the moment when the mollusk begins to cover its nucleus with nacre, until the fisher squeezes it from the folds of the creature's mantle, are many and varied. A few only escape untoward happenings. The fortunate, born where the mollusk gathers and spreads its choice secretions of mother-of-pearl, with room to grow on every side, are nursed in the lap of good fortune and uncheckered, round out layer by layer to perfection. But some are not so fortunate. In some way cramped, they are held against the unyielding shell and grow flat on one side. These are the button pearls. Others either from an irregular rolling, or unequal action of the mollusk's mantle, become imperfectly round. Sometimes foreign particles attach themselves to a growing pearl and becoming enveloped with it in future layers, make an uneven surface. Not infrequently two round pearls grow side by side until they touch, and together are enveloped by succeeding deposits; a twinned pearl is the result. For some reason, drop and pear-shaped pearls are seldom imperfect in shape. They may not be ideal but the form is usually good and the contour even and regular. This would imply that the simple rolling motion by the fish is more regular than the more complicated movements necessary to form a sphere.