All animals

as a general rule, are provided with eyes, excepting
the ostracoderms and other imperfect creatures; at all events, all
viviparous animals have eyes, with the exception of the mole. And
yet one might assert that, though the mole has not eyes in the full
sense, yet it has eyes in a kind of a way. For in point of absolute
fact it cannot see, and has no eyes visible externally; but when the
outer skin is removed, it is found to have the place where eyes are
usually situated, and the black parts of the eyes rightly situated,
and all the place that is usually devoted on the outside to eyes:
showing that the parts are stunted in development, and the skin
allowed to grow over.