Again: when an organism adapts itself to its environment, it does so by some modification being produced in its structure corresponding to the modified function required by the conditions of life. In this way, one organism increases in complexity in a certain direction, while another organism, in different circumstances, also develops a more complicated structure, though one of a different kind. Thus organisms, alike to begin with, become heterogeneous in nature through exposure to different surroundings. At the same time, by constant interaction with their environments, they become more definite and coherent in structure. Incipient modifications are developed and defined in different ways by different circumstances, and the parts of a living being are brought into closer reciprocal relations, and thus welded into a coherent organic whole. This is what Mr Spencer means when he says that evolution implies a transition from "an indefinite incoherent homogeneity to a definite coherent heterogeneity":[108] the whole process being interconnected in such a way that these different aspects of it--definiteness, coherence, heterogeneity--increase together and imply one another. By this the inference would appear to be suggested that, if conduct is to harmonise with the conditions of evolution, this characteristic feature of it must be recognised in the ethical end. [Sidenote: Distinction of its historical and ethical aspects.] In saying this, I am perhaps anticipating results. But it is well to show at the outset how the essentially historical inquiry carried out by the evolutionists may suggest conclusions which are ethical in their nature. To some, indeed, it will appear superfluous to have spent even a sentence in suggesting a _primâ facie_ case for the ethical importance of evolution. If there is one subject more than another, it may be thought, which has secured a place for itself in the scientific consciousness of the day, it is the evolution-theory of ethics. Without question, the phrase has been received into the scientific vocabulary; but there is a good deal, even in the official literature on the question, to make one doubt whether it is always used with a distinct conception of its meaning. When reference is made to the "ethics of evolution," no more is sometimes meant--though a great deal more should be meant--than an historical account of the growth of moral ideas and customs, which may provide (as Mr Stephen expresses it) "a new armoury wherewith to encounter certain plausible objections of the so-called Intuitionists." This, however, would only affect the ethical psychology of an opposed school. The profounder question still remains, What bearing has the theory of evolution, or its historical psychology and sociology, on the nature of the ethical end, or on the standard for distinguishing right and wrong in conduct? The answer to this question will be the "reconstruction"