Abstract
IN the last number of NATURE Mr. J. J. Murphy states the difficulty which he finds in accounting for the rise of intermittent variations upon the theory of natural selection. He can understand the origin of a white species from a brown one or vice versâ, but not of a species which, like the ermine, is at one season brown and at another season white. He speaks of “facts of colour which it seems impossible for natural selection to produce, from the infinite improbability of a first variation ever occurring.” From this mode of expression one might fancy that Mr. Murphy had for the moment forgotten that natural selection is in no way concerned with producing, but acts only by preserving, variations. As in a great number of instances we are ignorant of the precise antecedents which produce variation, whether chronic or recurrent, in such instances, we must be left at liberty, if we choose, to invoke the special action of “a guiding intelligence.” The case, however, of an animal which changes its colour with the season does not seem to be one of very exceptional difficulty. It is only necessary to suppose that the animal became possessed of pigments liable to be acted on in the required direction by the seasonal changes of light and heat. It might well be that with some animals the influence of the same changes would be in a direction just the opposite of what was useful to them. In that case the variety would stand but little chance of being preserved. Similar explanations hold with regard to the vegetable kingdom. I have now before me drawings of Sempervivum spinosum. The summer rosette is bright green in colour, with the leaves expanded, while the winter rosette is a compact little ball of a dull purple. Thus the plant prepares itself against the cold of winter and the dearth of nourishment which that season brings, but it is likely enough that cold and dearth in the first instance led to the variation in the plant from its summer habit.
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STEBBING, T. [Letters to Editor]. Nature 14, 330 (1876). https://doi.org/10.1038/014330a0
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DOI: https://doi.org/10.1038/014330a0
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