SPECIES, in Optics, the image painted on the retina by the rays of light reflected from the several points of the surface of an object, received by the pupil, and collected in their passage through the crystalline, &c. It has been a matter of dispute among philosophers, whether the species of objects which give the soul an occasion of seeing, be an effusion of the substance of the body; a mere impression which they make on all bodies under certain circumstances; or whether they are not some more subtle body, such as light. The moderns have decided this point by the invention of artificial eyes, in which the species of objects are received on paper, in the same manner as in the natural eye.