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NICOLAUS STENO 



up anew, perhaps, in the place of the earlier edge and, like 

 those same teeth, are gradually thrust outward. 



2. The formation of pearls, not only of those which, clinging 

 to the shells, have a form not quite round, but also of those 

 which, after the pores in the surface of the animal have closed, 

 acquire a round form within the pores themselves. For 

 between the integuments of pearls and the subdivisions of 

 shell of pearl-bearing mollusks there is merely this difference, 

 that the filaments of the shells are located in the same plane, 

 as it were, while the integuments of pearls have their filaments 

 p. 56. distributed over a spherical surface., 



A happy instance of this was furnished by a pearl which, 

 with others, I broke at your command. This pearl, although 

 white without, enclosed within it a black body resembling a 

 grain of pepper in both color and size ; in that black body the 

 position of the filaments tending toward the centre was very 

 clear, and the arrangements or spheres of the same filaments 

 could be distinguished. At the same time I saw: 



1. That the excrescences on various pearls are nothing else 

 than very small pearls enclosed by the same common crusts. 



2. That many pearls of yellowish hue are imbued with a 

 yellow color not only in the outermost surface of the sphere, 

 but in all the inner spheres ; so that it is thus no longer possi- 

 ble to doubt that the yellow color must be attributed to the 

 changing fluids of the animal, and that he who seeks to wash 

 it clear, washes an Ethiopian ; ^ unless the color has either been 

 acquired, as, for instance, the tint gained from being worn at 

 the throat, or else was yellow in the outermost sphere only, as 

 might be the case if, for instance, the fluids of the animal had 

 changed when the inner spheres were being formed. 



In view of these facts the mistake is apparent of those who, 

 without a knowledge of Nature, cleverly attempt the imitation 

 of pearls ; for hardly any one could assay that feat successfully 



' The allusion is to a fable of jEsop, who flourished about the middle of the sixth century, 

 B.C. (Halm, Fabulae Aesopicae, Leipzig, 1875, XIII) : 'A man bought an /Ethiopian believ- 

 ing his color to be what it was through the neglect of his former owner. Upon taking him 

 home, the new owner applied to him soaps of all kinds and tried to whiten him with baths of 

 every description. But he was unable to change the color and was ready to fall sick from his 

 toil. Characteristics remain what they were.' 



