"This theory dates from the oldest philosophy, and derives perhaps its best illustration from the newest. It is this: That Nature iterates her means perpetually on successive planes. In the old aphorism, Nature is always self-similar. In the plant, the eye or germinative point opens to a leaf, then to another leaf, with the power of transforming the leaf into radicle, stamen, pistil, petal, bract, sepal, or seed. The whole art of the plant is still to repeat leaf on leaf without end, the more or less of heat, light, moisture and food, determining the form it shall assume. In the animal, Nature makes a vertebra, or a spine of vertebrae, and helps herself by a new spine, with a limited power of modifying its form,—spine on spine, to the end of the world.
"A poetic anatomist, in our own day, teaches that a snake, being a horizontal line, and man, being an erect line, constitute a right angle; and, between the lines of this mystical quadrant, all animated beings find their place; and he assumes the hair-worm, the span-worm, or the snake, as the type or prediction of the spine.
"Manifestly, at the end of the spine, Nature puts out smaller spines, as arms; at the end of the arms, new spines, as hands; at the other end she repeats the process, as legs and feet. At the top of the column, she puts out another spine, which doubles or loops itself over, as a span-worm, into a ball, and forms the skull, with extremities again; the hands being now the upper jaw, the feet the lower jaw, the fingers and toes being represented this time
