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Show 322 SEXUAL SELECTION. PART II. Many of the lower animals, whether hermap~rodites or with the sexes separate, are ornamente~ w1t~1 the most brilliant tints, or are shaded and stnped m an elegant manner. This is the case with ·many corals and sea-anemonies (Actinere), with some jelly-fish (1\iedusre, Porpita, &c.), with some Planarire, Ascidians, numerous Star-fishes, Echini, &c. ; but we may concl~de from the reasons already indicated, namely the umon of the two sexes in some of these animals, the permanently affixed condition of others, and the low mental powers of all, that such colours do not s~rve as a sexual attraction, and have not been acqmred throuah sexual selection. With the higher animals 0 the case is very different; for with them when one sex is much more brilliantly or conspicuously coloured than the other, and there is no difference in the habits of the two sexes which will account for this difference we have reason to believe in the influence of sexual' selection; and this belief is strongly confirmed when the more ornamented individuals, which are almost always the males, display their attractions before the other sex. We may also extend this conclusion to both sexes, when coloured alike, if their colours are plainly analogous to those of one sex alone in certain other species of the same group. How, then, are we to account for the beautiful or even gorgeous colours of many animals in the lowest classes? It appears very doubtful whether such colours usually serve as a protection; but we are extremely liable to err in regard to characters of all kinds in relation to protection, as will be admitted by every one who has read Mr. Wallace's excellent essay on this subject. It would not, for instance, at first occur to any one that the perfect transparency of the Medusre, or jelly-fishes, was of the highest service to them as a CHAP. IX. SEXUAL SELECTION. 323 protection; but when we are reminded by Hackel that not only the medusre but many floating mollusca, crustaceans, and even small oceanic £shes partake of this same glass-like structure, we can hardly doubt that they thus escape the notice of pelagic birds and other enemies. Notwithstanding our ignorance how far colour in many cases serves as a protection, the most probable view in regard to the splendid tints of many of the lowest animals seems to be that their colours are the direct result either of the chemical nature or the minute structure of their tissues, independently of any benefit thus derived. Hardly any colour is finer than that of arterial blood; but there is no reason to suppose that the colour of the blood is in itself any advantage; and though it adds to the beauty of the maiden's cheek, no one will pretend that it has been acquired for this purpose. So again with many animals, especially the lower ones, the bile is richly coloured; thus the extreme beauty of the Eolidre (naked sea-slugs) is chiefly due, as I am informed by Mr. Hancock, to the biliary glands seen through the translucent integuments ; this beauty being probably of no service to these animals. The tints of the decaying leaves in an American forest are described by every one as gorgeous ; yet no one supposes that these tints are of the least advantage to the trees. Bearing in mind how many substances closely analogous to natural organic compounds have been recently formed by chemists, and which exhibit the most splendid colours, it would have been a strange fact if substances similarly coloured had not often originated, independently of any useful end being thus gained, in the complex laboratory of living organisms. y 2 |