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Show 198 DARWINISM OHAP. from dusky through pinkish to palo green. It is interesting to JLOto, that tho colours produced wore in nil cn.scs SIH.:h only as assimilated with the surroundings usually occupied by the species, and also, that colours which did not occur in such surroundings, as cla.rk red or blue, only produced the same effccLs as dusky or bbck Oa.rcful experiments were made to a.sccrta.in whether the effect wa.s produced through the sight of the ca.tcrpillar. Tlw ocelli were covered with black varnish, but neither this, nor cutting off the spines of tho tortoise-shell brva to ascert:Li 11 whether they might be sense-organs, produced any effect 011 tho resulting colour. Mr. Poulton concludes, therefore, that the colour-action probably occurs over the whole surface of tho body, setting up physiological processes which result in the corresponding colour-change of the pupa. Such changes are, however, by no means univorsa1, or even common, in protectively coloured pupm, since in Papilio machaon all<l some others which have been experimented on, both in this country and abroa.d, no cha.nge can be produced on the pllpn. by n.ny amount of exposure to differently colonrcd snrrmuHlings. It is a, curious point that, with the small tortoise slwll htrv:.t, exposure to light from gilded snrfaccs proclnced pupm with a brmittnt golden lustre; and the cxplana.tion is supposrd to be that mica. abounded in the original lmbit<tt of tho :pecies, and that the pnpm thus obtained protection when snspcn<lcd against micaceous rock Looking, however, at the wide range of the species and the comparatively limited area in which micaceous rocks occur, this seems a mthor improh:tl,]o explanation, and the occurrence of this metallic appear: I nee is still a difficulty. It docs not, however, commonly ocwr in this conn try in :t nn,tu.ntl state. The two classes of variable colonri r1g here d iscussrd are evidently exceptional, :ul(l c:w h~tvc little if any n'lat io11 to tho colonr. of tho. e more :u.:tivc crc;l,Ltu·es whicl1 :Ln~ toll1illlt: tlly ch:tnging their po. ition with regard to stuTounding ol'jl'ds, ltnd whose colours and markings aro 11 'arly cmr st:wt Lhronghout the life of the individual, mHl (with the exception of sexual differences) in n.ll the indivichmls of tlw species. \\To will now hricfly p.tss in r 'view the v:trions cl1 am.dcristi c!-i and uses of the colours which more generally prcv<.til in nature; vnr ORIGIN AND USES OF COLOUR IN ANIMALS 199 and having already discussed those protective colours which serve to harmonise animals with their gcneml environment, we have to con. iclcr only those cases in which the colour resemblance is more local or special in its character. Special or Local Colou1· Adaptations. This form of colour adaptation is generally manifested by markings rather than by colour alone, and is extremely prevalent both a.mong insects and vertebrates, so that we shall be able to notice only a few illustrative caPes. Among our native birds we have the snipe and woodcock, whose marki11gs and tints strikingly accord with the dead marsh vegetation among which they live; the ptarmigan in its ummer clre::;s is mottled and tinted exactly like the lichens which cover the stones of the higher mountains; while young unfledged plovers arc spotted so as exactly to resemble the beach pebbles among which they crouch for protection, as beautifully exhibited in one of the cases of British birds in the N a.tural History Museum at South Kensington. In mammalia, we notiee tho frequency of rounded . pots on forest or tree haunting lmimals of largo size, as the forest deer and the forest cats; while those that freqncnt roe ly or gmssy places are striped vertically, as the mn,rsh a.ntelopcs and the tiger. I had long been of opinion that the brilliant yellow and black stripes of tho tiger were adaptive, but have only recently obtained proof that it is so. An experienced tiger-hunter, Major vV a.lfonl, st<ttes in a letter, that tho haunts of the tiger arc inva.ria.hly fnll of the long grass, dry and pttle yellow for at least nine months of the year, which covers the ground wherever there is water in the rainy season, and he adds : "I once, while following up a wounded tiger, failed for at least a minute to sec him under a tree in grass at a eli tance of about twenty yards-jungle open-but the n:ttivos aw him, and I eventually made him out well enough to shoot him, but oven then I could not sec at what part of him I was aiming. There can be no doubt whatever that the colour of both the tiger a.nd the panther renders them ::t.lmost invi ihlc, especially in :t strono· hlar.c of light, when among gn~.>c;s, ltllcl one doe not seem to 11oticc stripes or spots till they are dead." It is the black sha.dows of the vegetation that. |