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Show 480 CONCLUSION. CHAP. XIV. of life; and we can clearly understand ~n this view the meaning of rudimentary organs. But disuse and. selection will generally act on eac.h cre~ture, when ~t has come to maturity and has to. play Its full ~art In the struggle for existence, and will th~s have httle power of actino· on an organ during early hfe; hence the organ will nof be much reduced or rendered rudimentary at this early age. The calf, for instance, has inherited teeth which never cut through the gums of the upper jaw 'from an early progenitor having well-developed teeth ; and we may believe, that the teeth in the mature animal were reduced, during successive generations, by disuse or by the tongue and palate having been fitted by natural selection to browse without thoir aid· whereas in the calf, the teeth have been left untou~ hed by selection or disuse, and on the principle of inheritance at corresponding ages have been inherited from a remote period to the present day. On the view of each organic being and each separat~ orga~ ~aving been specially created, how utterly Ine:phcable It. Is that parts, like the teeth in the embryo~IC calf or hke the shrivelled wings under the soldered wing-covers of some beetles should thus so frequently bear the plain stamp of inutility! Nature may be said to have taken pains to reveal, by rudimentary organs and by homologous strnctures, her scheme of modification, which it seems that we wilfully will not understand. I have now recapitulated the chief facts and consid~rations which have thoroughly convinced me that speCJes have chanO'ed and are still slowly changing by the preservation ~nd' accumulation of successive slight favourable variations. Why, it may be asked, h.ave a~l the mo t eminent living naturalists and geologists reJected this view of the mutability of species? It cannot be CHAP. XIV. CONCLUSION. 481 asserted that organic beings in state f su b~.e c t t o no van·a tw· n · I. t cannoat b o nda tuhr e are amount of van·a ti.o n I.n ' the course oe f p1ro ve t at ·t he lim i·t e d quanti· ty; no clear distinction haos nbg ages Is a een, or can be, drawn betwe.e n .s pecies and well-marl,r,_ ed varw· tI' es. It ca. nnot. bbel mainta. ined that species when inter crosse d are Invana . ~ st~rile, and. varieties invariably fertile; or t~at stenhty I~ a special ~ndowment and sign of creation. The behef that species were immutable pro~ ductions was almost unavoidable as long as the history of the world was thought to be of short duration . and n_ow that we have acquired some idea of the la~se of time, ~e are too ap~ to assume, without proof, that the geologiCal record Is so perfect that it would have afforded us plain evidence of the mutation of specie~ if they had undergone mutation. B~t the chief cams~ of our natural unwillingness to admit that one species has given birth to other and distinct species, is that ':e are always slow in admitting any great change of whwh we do not see the intermediate steps. T~e difficulty is the same as that felt by so many geologists, when Lyell first insisted that long lines of inland cliffs had been formed, and great valleys excavated, by the slow action of the coast-waves. The mind cannot possibly grasp the full meaning of the term of ~ hundred million years; it cannot add up and perceive the full effects of many slight variations, accumulated during an almost infinite number of ge~ nerations. Although I am fully convinced of the truth of the views . given in t4is volume under the form of an abstract, I by no means expect to convince experienced naturalists whose minds are stocked with a multitude of fa_cts all :iewed, during a long course of years, from a p01nt of VIew directly opposite to mine. It is so easy y |