aggregates into the motion of units. The formula equally applies to the dissolution of a society. When social ties, be they governmental or industrial, are destroyed, the combined actions of citizens lapse into uncombined actions. Those general forces which restrained individual doings, having disappeared, the only remaining restraints are those separately exercised by individuals on each other. There are no longer any of the joint operations by which men satisfy their wants; and, in so far as they can, they satisfy their wants by separate operations. That is to say, the movement of parts replaces the movement of wholes. Under its dynamical aspect then, Evolution, so far as we can trace it, is a change from molecular motion to the motion of masses; while Dissolution, so far as we can trace it, is a change from the motion of masses to molecular motion. * * * * * § 106. To these abstract definitions may be added concrete ones. Besides an integration of motions corresponding to the integration of masses, Evolution involves an increase in the multiformity of the motions, corresponding to the increase in the multiformity of the masses. If, contemplating it as materially displayed, we find Evolution to consist in the change from an indefinite, homogeneous distribution of parts to a definite, heterogeneous distribution of parts; then, contemplating Evolution as dynamically displayed, it consists in a change from indefinite, homogeneous motions to definite, heterogeneous motions.