678 THE POPULAR SCIENCE MONTHLY. 



the inherent tendencies to dissolution. The eqviilibrimn reached is 

 between the attractive or integrating and the repulsive or disinte- 

 grating forces. Both are at all times active, and, if the latter at last 

 prevail and the mode of redistribution is reversed, the gravitative in- 

 fluence still continues to oppose its progress. In an organism the dis- 

 integrating 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 pre- 

 vails. 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 prin- 

 ciple 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 j^lace. In the case 

 of the earth the atmosphere or gaseous portion forms a uniform en- 

 velope around it, due clearly to the nature and homogeneity of its 

 molecular constitution. The waters, for the same reason, form a par- 

 tial 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 differ- 

 entiated parts, are tlie 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 : Organiza- 

 tion is the necessary consequence of the competition of the integrat- 

 ing and disintegrating forces, so long as the former prevail. The 

 influence of the sim upon the matter of the globe is toward its disin- 

 tegration 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 evo- 

 lution which we denominate organic life. A certain amount of the 



