Page:The Zoologist, 4th series, vol 2 (1898).djvu/421

Rh in the lives and development of these creatures, connected and increasing with an advancing animal evolution, but still only a term to express the modifying influences incidental to a struggle for existence. In fact, natural selection is more an effect than a cause. It was incidental and consequent to the progress of evolution in animal life, and ever increasing its sway in ratio with the vast increase of living things became the giant modifying influence, and modelled, painted, exterminated, and sustained the fauna and flora which by their dangerous fecundity came under her rule. But because a phenomenon is ancient it is not necessarily eternal—theologians discuss those questions—and if logic imperatively demands an antecedent to natural selection, biology must refuse to recognize that undoubtedly mighty and modifying influence as a First Cause. "We attach too exclusive an importance to adaptation... when we think to explain by selection every similarity between the colouring of an animal and that of the ground on which it lives. For, as we have seen, animals may become similar in colour to their surroundings, actually adapted in colour, quite by chance; for instance, in consequence of the direct necessary action of light, i.e. of the surrounding colours, and therefore without selection, many really wonderful cases of adaptation, apparently due to selection, probably come under the category."

It seems a probable suggestion that assimilative colouration was a very constant factor in an early stage of animal life, and