The unio is a slow growing animal. Under normal conditions it takes ten years for a nigger-head to reach a size of three inches; fifteen to eighteen years to attain a shell diameter of 4-1/2 inches. This corresponds very closely with the life of the meleagrina, though the shell of the latter ceases to grow in size at about eight or ten years. After that it continues to lay on thickness up to eighteen or twenty years. Although the discoveries so far in Africa are unimportant, it is possible, now that the unio is known to exist there, that the streams of that wonderful land of precious things may add a companion gem to the vast natural hoards there of the diamond. In two years succeeding his first find, the discoverer secured one hundred and fifty pearls at an average of one pearl to eight hundred shells. Authorities tell us that the nucleus of a mussel-pearl is usually the larva of a distoma. Nuclei of pearls vary according to the circumstances surrounding the beds of the shell-fish and those circumstances have much to do with the occurrence of the pearl. PRICE Value, except in things which are constant and constantly changing hands, is a matter of opinion. Price is the expression of that opinion in money terms. Except in a few staple sizes and qualities, pearls are affected by so many details which determine their value that it is difficult to formulate rules to correspond and establish a base by which all may be judged. Shape, size, color, luster, and perfection, afford a multiplicity of combinations sufficient to puzzle the judgment of the most expert, and when to this is added the fact that there is no other one like the piece to be valued so as to gauge opinion, there remains but one finality, the agreement between buyer and seller on a price. Disregarding the fluctuations of price occasioned by temporary influences and the variations arising from local causes, this chapter is intended to give information of the price of pearls in the United States to retail dealers, and an idea of the relative value of different qualities and shapes.