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Show 198 DIFFICULTIES ON THEORY. Cn.AP. VI. ately made conscious of this by reflec_ting on t~e diffe:ences in the breeds of our domesticated animals In different countries -more especially in the less civilized countries where there has been but little artificial selection. Careful observers. are convinced that a damp climate affects the growth of the hair, and that with the hair the horns are correlated. Mountain breeds always differ from lowland breeds ; and a mountainous country would probably affect the hind limbs from exercising them more, and possibly even the form of the pelvis ; and then by the law of homologous variation, the front limbs and even the head would probably be affected. The shape, also, of the pelvis might affect by pressure the shape of the head of the young in the womb. The laborious breathing necessary in high regions would, we have some reason to believe, increase the size of the chest; and again correlation would come into play. Animals kept by savages in different countries often have to struggle for their own subsistence, and would be exposed to a certain extent to natural selection, and individuals with slightly different constitutions would succeed best under different climates ; and there is reason to believe that constitution and colour are correlated. A good observer, also, states that in cattle susceptibility to the attacks of flies is correlated with colour, as is the liability to be poisoned by certain plants; so that colour would be thus subjected to the action of natural selection. But we are far too ignorant to speculate on the relative importance of the several known and unknown laws of variation; and I have here alluded to them only to show that, if we are unable to account for the characteristic differences of our domestic breeds, which nevertheless we generally admit to have arisen through ordinary generation, we ought not to lay too much stress on our CHAP. VI. ORG . ANS OF LITTLE IMPORTANCE. 199 I~norance of the precise cause of th . differences between specie I . e slight analogous this same purpose the d.~· might have adduced for man, which are so stro~gelyrencesl bedtween the races of I . . mar re · I m dd some Ittle hght can apparent! b tl ' ay a that of these differences chiefi tl ~ e lrown on the origin a particular kind b~t withy tnhough sex~al selection of d il ' ou ere entermg · . eta s my reasoning would f. on copious Th £ . appear rivolous e oregmng remarks lead me t . on the protest lately made b o say~ few words the utilitarian doctrine th [some naturalists, against has been produced for the a oo~verJ. detail of structure believe that very many stru~ture o Its possessor. They beauty in the eyes of m £shave been created for d an, or or mere . t octrine, if true, would be absolut l vane y. This Yet I fully admit that m t e y fatal to my theory: t · any s ruetures are of di use o their possessors Ph . . . no rect have had some little . J!(' t ysical conditions probably euec on structu · t · pendently of any good th . re, qui e Inde-growth has no doubt' la ed u: gtun~d. Correlation of a useful modifi.catio! J most ~portant part, and tailed on other parts di o ~~e dp~t Will often have enSo again characters ;~~s~ e£ c anges ofno direct use. which formerly had .· c f ormerly were useful, or or from other k ansen rom co rre1 a tI' on of . growth un nown cause ' law of reversion th h ' may reappear from the effects of sexual 'sel o~? now of ~o direct use. The charm the femaies ec I~n, when displayed in beauty to a. forced sense. :B:nb e £called useful. only in rather Sideration is that th ~ far the most rmportant conevery being is s. ~ c e part of the organisation of ~uently, though~:~~ d~e to inherita~ce; and conseIts place in nat bemg assuredly IS well fitted for relation to th uhreb, .many structures now have no direct can hardly beel i a Ittsh of life of each speci·e s. Thus we eve at the webbed feet of the upland |