And so we reach the remarkable conclusion that the life of a species, like the life of an individual, is maintained by the unequal and ever-varying actions of incident forces on its different parts.[40] An individual homogeneous throughout, and having its substance everywhere continuously subject to like actions, could undergo none of those changes which life consists of; and similarly, an absolutely-uniform species, having all its members exposed to identical influences, would be deprived of that initiator of change which maintains its existence as a species. Just as, in each organism, incident forces constantly produce divergences from the mean state in various directions, which are constantly balanced by opposite divergences indirectly produced by other incident forces; and just as the combination of rhythmical functions thus maintained, constitutes the life of the organism; so, in a species, there is, through gamogenesis, a perpetual neutralization of those contrary deviations from the mean state which are caused in its different parts by different sets of incident forces; and it is similarly by the rhythmical production and compensation of these contrary deviations, that the species continues to live. The moving equilibrium in a species, like the moving equilibrium in an individual, would rapidly end in complete equilibration, or death, were not its continually-dissipated forces continually re-supplied from without. Besides owing to the external world those energies which, from moment to moment, keep up the lives of its individual members, every species owes to certain more indirect actions of the external world, those energies which enable it to perpetuate itself in successive generations. § 97. What evidence still remains may be conveniently woven up along with a recapitulation of the argument pursued through the last three chapters. Let us contemplate the facts in their synthetic order.