Evolution, then, is in all cases a change from a more diffused or incoherent form, to a more consolidated or coherent form. This proves to be a characteristic displayed equally in those earliest changes which the Universe as a whole is supposed to have undergone, and in those latest changes which we trace in society and the products of social life. Nor is it only that in the development of a planet, of an organism, of a society, of a science, of an art, the process of integration is seen in a more complete aggregation of each whole and of its constituent parts; but it is also shown in an increasing mutual dependence of the parts. Dimly foreshadowed as this mutual dependence is among inorganic phenomena, both celestial and terrestrial, it becomes distinct among organic phenomena. From the lowest living forms upwards, the degree of development is marked by the degree in which the several parts constitute a mutually-dependent whole. The advance from those creatures which live on in each part when cut in pieces, up to those creatures which cannot lose any considerable part without death, nor any inconsiderable part without great constitutional disturbance, is clearly an advance to creatures which are not only more integrated in respect of their solidification, but are also more integrated as consisting of organs that live for and by each other. The like contrast between undeveloped and developed societies, need not be shown in detail: the ever-increasing co-ordination of parts, is conspicuous to all. And it must suffice just to indicate that the same thing holds true of social products: as, for instance, of Science; which has become highly integrated not only in the sense that each division is made up of mutually-dependent propositions, but also in the sense that the several divisions are mutually-dependent—cannot carry on their respective investigations without aid from each other.