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Show 100 DARWINISM CllAP. been able to increase them to a marvellous extent by the simple process of always preserving the best varieties to breed from. Along with these larger variations others of smaller amount occasioually appear, sometimes in external, sometime:-: in internal characters, the very bones of the skeleton often changing slightly in form, size, or number; but as these secondary characters have been of no usc to man, and h:we not been specially selected by him, they have, usually, not been developed to any great amount except when they ha.vc been closely dependent on those external characters which he has largely modified. As man has considered only utility to himself, or the satisfaction of his love of beauty, of novelty, or merely of something strange or amusing, the variations he has thus produced have something of the character of monstrosities. Not only are they often of no use to the animals or plants them selves, but they are not unfrcquently injurious to them. l ll the Tumbler pigeons, for instance, the habit of tumblin <r is sometime~ so excessive ~s to injure or kill the bird; and m~ny of our highly-bred ammals have such dehcatc constitutions that they are very liable to disease, while their cxtrenw peculiarities of form or structure would often render them quite unfit to live in a wild state. In plants, many of our dou_ble flowers, and some fruits, have lost the power of producmg seed, and the race can thus be continued only by means of cuttings or grafts. This peculiar character of domestic productions distinguishes them broadly from wild species anrl varieties, which, as will be seen by and by, arc necessarily adapted in every part of their organisation to the conditions under which they have to live. Their importance for our pr~sent inquiry depends on their demonstmting the occuncncc of mcessant slight variations in all parts of an organism, with the transmission to the offspring of the special charactcrdics of the parents ; and also, that all such sli O'ht Yariations arc capable of being accumulated by selection btill they present very large and important divergencies from the ancestral stock. W o thus see, that the evidence as to variation afforded by animals and plants under domestication strikino·ly nccords with that which we have proved to exist in a stateb of nature. IV VARIATION UNDER DOMESTICATION 101 And it is not at all surprising that it should be so, sin?e all tho species wore in a state of nature when first domesticated or cultivated by man, and whatever variations occur ~ust he due to purely natural causes. Moreover,. on compann~ the v:uiations which occur in any one generation. of d_omcst~catcd animals with those which we know to occur m :vii~ at:Imals, we find no evidence of greater individual v~natwn _m tho former than in the bttcr. Tho results of mans se~ectwn arc more striking to us because we have a.lways ~onsicl_cred . tho varieties of each domestic animal to be essentw1ly Identical, while those which we observe in a. wild sta.tc arc hold to be essentially diverse. Tho groyhou!ld and the spaniel cc~ wonderful as va.rieties of one ammal produced by mans selection;' while we think little of the diversities of the fox and the wolf or the horse and the zebra, because we have been accusto~cd to look upon them as radica1ly di tinct animals, not as the results of nature's selection of the varieties of a common ancestor. |