CENTENINUM ovum, among naturalists, denotes a sort of hen's egg much smaller than ordinary, vulgarly called a cock's egg; from which it has been fabulously held that the cockatrice or basilisk is produced. The name is taken from an opinion, that these are the last eggs which hens lay, having laid 100 before; whence centenium, q. d. the hundredth egg.—These eggs have no yolks, but in other respects differ not from common ones; having the albumen, chalazae, membranes, &c. in common with others. In the place of the yolk is found a little body like a serpent coiled up, which doubtless gave rise to the fable of the basilisk's origin from thence. Their origin is with probability ascribed by Hervey to this, that the yolks in the vitellary of the hen are exhausted before the albumina.