the inherent tendencies to dissolution. The equilibrium reached is between the attractive or integrating and the repulsive or disintegrating forces. Both are at all times active, and, if the latter at last prevail and the mode of redistribution is reversed, the gravitative influence still continues to oppose its progress. In an organism the disintegrating tendencies are chiefly from without. Everywhere on the globe the sun's influence is tending to prevent the integration of the liquid and gaseous elements. Life is the product of this struggle.
It may be laid down, as a universal law of the redistribution of matter, that organization is the product of the antagonistic tendencies of attraction and repulsion during the period in which the former prevails. Organization is, then, the great distinguishing characteristic of the process of evolution. The organization of the solar system is the result of this competitive struggle between these two agencies. It is the same with an organism. We have, then, at last reached a plane of generalization in which the cosmical and the organic processes may be regarded as parallel and homologous throughout. The active principle which directly results in organization is that which Mr. Spencer denominates segregation, by which the like parts are brought together and unlike parts separated.
The final result of this process is the formation of many distinct and definite parts which are unlike one another—heterogeneous. Each of these definite parts, differing from all the rest in the same aggregate, is, within itself, homogeneous, i. e., consists of a uniform internal structure. The like particles, in consequence of the similarity of their properties, naturally gravitate to the same place. In the case of the earth the atmosphere or gaseous portion forms a uniform envelope around it, due clearly to the nature and homogeneity of its molecular constitution. The waters, for the same reason, form a partial second envelope within this. The hardened crust of solid matter comes next, and in like manner the entire organization of the earth might be explained. Exactly the same process takes place in a living organism. Its various organs, vessels, specialized tissues, and differentiated parts, are the result of this same law of mechanical selection. The difference in the properties of the matter of each is at once the cause of their segregation and of their organic function.
The point at which we have arrived, therefore, is this: Organization is the necessary consequence of the competition of the integrating and disintegrating forces, so long as the former prevail. The influence of the sim upon the matter of the globe is toward its disintegration and dissipation into gas. But for the opposing influence of gravitation, attraction, or concentration, this result would be speedily accomplished. But the resultant of these two antagonistic forces, at a time when their relative power is substantially what it now is on the surface of our globe, is such as to render possible the form of evolution which we denominate organic life. A certain amount of the
