l conform. And similarly in every
other case. Leaving out of sight concomitants and beneficial
consequences, let us ask what progress is in itself.

In respect to that progress which individual organisms display in the
course of their evolution, this question has been answered by the
Germans. The investigations of Wolff, Goethe, and von Baer, have
established the truth that the series of changes gone through during the
development of a seed into a tree, or an ovum into an animal, constitute
an advance from homogeneity of structure to heterogeneity of structure.
In its primary stage, every germ consists of a substance that is uniform
throughout, both in texture and chemical composition. The first step is
the appearance of a difference between two parts of this substance; or,
as the phenomenon is called in physiological language, a
differentiation. Each of these differentiated divisions presently begins
itself to exhibit some contrast of parts: and by and by these secondary
differentiations become as definite as the original one. This process is
continuously repeated--is simultaneously going on in all parts of the
growing embryo; and by endless such differentiations there is finally
produced that complex combination of tissues and organs constituting the
adult animal or plant. This is the history of all organisms whatever. It
is settled beyond dispute that organic progress consists in a change
from the homogeneous to the heterogeneous.

Now, we propose in the first place to show, that this law of organic
progress is the law of all progress. Whether it be in the development of
the Earth, in the development of Life upon its surface, in the
development of Society, of Government, of Manufactures, of Commerce, of
Language, Literature, Science, Art, this same evolution of the simple
into the complex, through successive differentiations, holds throughout.
From the earliest traceable cosmical changes down to the latest results
of civilization, we shall find that the transformation of the
homogeneous into the heterogeneous, is that in which progress
essentially consists.

With the view of showing that _if_ the Nebular Hypothesis be true, the
genesis of the solar system supplies one illustration of this law, let
us assume that the matter of which the sun and planets consist was once
in a diffused form; and that from the gravitation of its atoms there
resulted a gradual concentration. By the hypothesis, the solar system in
its na