When we look at the animal kingdom, we recognize there also the
presence of simple, all-pervading laws. The four great types of animal
structures are readily discerned by the dullest eye: no man fails to
see the likeness among all vertebrates, or the likeness among all
articulates, the likeness among alt mollusks, or the likeness among all
radiates. These four types show, moreover, a certain unity, even to the
untaught eye: we call them all by one name, animals, and feel that
there is a likeness between them deeper than the widest differences in
their structure; there are analogies where there are not homologies.

The difference between the four types of animals is marked at a very
early period in the embryo,--the embryo taking one of four different
forms, according to the department to which it belongs; and Peirce has
shown that these four forms are all embodiments of one single law of
position. If, then, one single algebraic law of form includes the four
diverse forms of the four great branches of the animal kingdom, is it
extravagant to suppose that the diversities in each branch are also
capable of being included in simple generalizations of form? Is it
unreasonable to believe that the exceeding beauty of animated forms,
and of the highest, the human form, arises from the fact that these
forms are the result of some simple intellectual law, a simple
conception of the Divine Geometer, assuming varied developments in the
great series of animated beings? It is the unity of the form, arising
from the simplicity of its law, and the multiplicity of its
manifestations or details, arising from the generality of its law,
that, intuitively perceived by the eye, although the intellect may not
apprehend them, give the charm to the figures of the animate creation.

The subject, even in the narrow limits which we have imposed upon