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Show 218 DARWINISM CHAP. The wonderful diversity of colour and of marking that prevails especially in birds and insects, may be due to the fact that 'one of the first needs of a new sp.ccies would be, to kc.cp separate from its nearest allies, and th1s coul~ be most readily done by some easily seen external m~rk ~f ~1ffcrenc~. A few illustrations will serve to show how this prmcrplc acts m nature. My attention was first called to the subJect by a re~arlc of Mr. Darwin's that, though, " the hare on her form IS a f<tmiliar instance of concealment through colour, yet the principle partly fails in a closel! a~lied species, t~e rabbit; for when running to its burrow It IS made conspi~uous to the sportsman, and no doubt to all ?easts. of prey, by 1ts .upturned white tail." I But a little consHlcratwn of the hab1ts of tho animal will show that the white upturned tail is of the greatest value and is really, as it has been termed by a ·writer in J'he Field,' a "signal ftag of danger." For the rabbit is usual~y <t crepuscular animal, feeding soon after. sunset or on. moonhght nights. When disturbed ~r alarmed I~ makes for 1ts bun:ow, and the white upturned tails of those m front serve as gmd<'s and sirrnals to those more remote from home, to the young ancl • the fc~ble; and thus each following the one or two before it, all are able with the least possible delay to regain a place of comparative safety. The apparent danger, therefore, becomes a most important means of security. The same general principle enables us to understand the singular, and often conspicuous, marking on so many gregarious herbivora which are yet, on the whole, protectively coloured. Thus, the American prong-buck llas a white patch bchi ll(l and a black muzzle. The Tartarian antelope, the Ovis poli of Hi&h Asia, the Java wild ox, several species of deer, ancl a hrge ~umber of antelopes have a similar conspicuous while patch behind, which, in contrast to the ~usky body, m~st en a hle them to be seen and followed from a d1stancc by their fell ows. \Vherc there arc many species of nearly the same gen ral size and form inhabiting the same region-as with the antelopes wa~ the same. This is precisely what we should expect if the symmetry is not the result of a general law oft he organisation, but has been! !II par'L at l eas~, Jll'~clnced and preserved for the useful purpose of recognrtron hy the amrm~l s fellows of the same species, ancl especially by the sexes aml the young. See Proc. qf the .Am . .Ass. joT Advancement of &ience, Yol. xxx. p. 246. 1 J)escent of .!Jfan, p. 542. VIII ORIGIN AND USES O.F COLOUR IN ANIMALS 219 of Africa-we find many distinctive markings of a similar kind. The gazelles have variously striped and banded faces, besides white patches behind and on the flanks, as shown in the woodcut. The spring-bok has a white patch on the face and one on the sides, with a curiou. ly distinctive white stripe above the tail, which is nearly concealed when the animal is at rest by a fold of skin but comes into full view when it is in motion, being thns qnitc analogous to the Fro. 18.-Gazclla smmmerringi. upturned white tail of the rabbit. In the pallah the white rump-mark is bordered with black, and the peculiar shn.pc of the horns distino·nishes it when seen from the front. The sable-antelope, the gems-bok, the oryx, the hartbcest, the bonte-bok, and the addax have each peculiar white markings ; and they arc besides characterised by horns so remarkably different in each species and so conspicuous, that it seems probable that the peculiarities in length, twist, and curvature have been differentiated for the purpose of recognition, rather than for any speciality of defence in species whose general habits are so similar. |
