On the production and formation of pearls

Abstract

In his examinations of the organs of generation of the large freshwater muscle, the author often met with seed pearls, either in the ovarium, or connected with the shell upon which the ovarium lay; and he remarked at the same time that all Oriental pearls have a brilliant central cell, which in the common mode of boring them is destroyed, but which may be beautifully exhibited by carefully splitting the pearl into halves: this cell is just large enough to contain an ovum, which is formed upon a pedicle like the yolk of the pullet’s egg, and is similarly discharged when completely formed. Thence Sir Everard concludes, that a pearl is formed upon the external surface of an ovum, which having been blighted, does not pass with the others into the oviduct, but remains attached to its pedicle in the ovarium, and in the following season receives a coat of pearl at the same time that the inner surface of the shell receives its annual supply. This conclusion, he observes, is verified by some pearls being spherical while others are pyramidal, in consequence of the pedicle, as well as the ovum, having been enamelled with nacre. This paper concludes with an extract from one of the early volumes of the Philosophical Transactions, in which a corresponding account of the growth of pearls is announced by Arnoldi in 1673.