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in the rough, but gradually in more and more minute detail. This adaptation, brought about by chance, gives _the impression_ of intelligent creative purpose. In Darwin this fundamental mode of naturalistic interpretation took, under the influence of the social-economic theories of Malthus, the special form of natural selection by means of the struggle for existence, in association with the assumption of unlimited and fluctuating variability in the forms of life. All living beings have a tendency to increase in number without limit. But the means of subsistence and other conditions of existence do not increase at the same rate; they are relatively constant. Thus competition must come about. Any organism that is, by fortuitous variation, more favourably equipped than its fellows maintains itself and reproduces itself; the less favoured perish. For all things living are exposed to enemies, to untoward circumstances, and the like. Every individual favoured above its rivals persists, and can transmit to its descendants its own more favourable, more differentiated, more highly equipped character. Thus evolution is begun, and is forced on into the ever more diverse and ever "higher." To Darwin this struggle for existence and this selection according to utility seemed, at any rate, the chief factor in progress. He did, indeed, make some concessions to the Lamarckian principle that new characters may be acquired by increased use, and to other "secondary" principles. But these are of small importance as compared with his main factor. Differences of Opinion As To the Factors In Evolution. The theory of natural selection in the struggle for existence rapidly gained wide acceptance, but from the first it was called in question from many sides. Bronn, who translated Darwin's works into German, was and remained loyal to the idea of a "developmental law"--that there is within the organism an innate tendency towards self-differentiation and progress, thus a purely teleological principle.(34) Similarly, von Baer emphasised the idea of an endeavour to realise an aim; von Koelliker, that of "heterogenesis"; Naegeli, that of an impulse towards perfection--all three thus recognising the theory of evolution, but dissenting from the view that the struggle for existence is the impelling factor and actual guide in the process. Very soon, in another direction, antagonism became pronounced between the strictly Darwinian elements of
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