The old theory of dew-formed pearls was illustrated even as late as 1684 on a medal struck in honor of Elena Piscopia of the Corraro family of Venice. This bore an oyster-shell open and receiving drops of dew, and underneath was engraved the motto “_Rore divino_” (By divine dew). Even yet one hears occasionally from out-of-the-way places—as in the instance reported by the American consul at Aden—of pearls formed from rain or dew, notwithstanding that there seems to exist absolutely no justification for it in scientific zoölogy. Probably the most popular theory entertained from the fifteenth to the seventeenth century was that pearls were formed from the eggs of the oyster. This was intimated by Chauveton in the quotation above given, and it was also referred to by many naturalists. In an interesting letter, dated Dec. 1, 1673, and giving as his authority the testimony of an eye-witness, “Henricus Arnoldi, an ingenious and veracious Dane,” Christopher Sandius wrote: “Pearl shells in Norway do breed in sweet waters; their shells are like mussels, but larger; the fish is like an oyster, it produces clusters of eggs; these, when ripe, are cast out and become like those that cast them; but sometimes it appears that one or two of these eggs stick fast to the side of the matrix, and are not voided with the rest. These are fed by the oyster against her will and they do grow, according to the length of time, into pearls of different bigness.”[47] This possibly hit the mark with greater accuracy than the observations of the “ingenious and veracious Dane” warranted, for he seems to have had quite a different idea as to the manner in which the pearls are “fed by the oyster against her will” from those generally entertained by naturalists at the present time. However, Oliver Goldsmith settled the matter by declaring briefly: “Whether pearls be a disease or an accident in the animal is scarce worth enquiry.”[48] Thus it seems that notwithstanding all that had been written and the extended attention given to the subject, theory prevailed to the almost complete exclusion of practical investigation, with little intelligent advance over Topsy’s “’spect they just growed.” Owing, doubtless, to the scarcity of pearl-bearing mollusks in their vicinities, naturalists of Europe were somewhat slow in giving attention to the origin of pearls. This is further accounted for by the fact that the gems occur more frequently in old and diseased shells than in the choice specimens which have naturally attracted the notice of conchologists. One of the first of the original observations made on this subject was that by Rondelet, who, in 1554, advanced the idea that pearls are diseased concretions occurring in the mollusca, similar to the morbid calculi in the mammalia.[49]