OCR Text |
Show 262 IMPERFECTION OF THE [CARP. IX. specifically distinct. This could be. effected only by t~e future geologist discovering in a fossil state numerous _Intermediate gradations ; and such success seems to n1e Improbable in the highest degree. . Geological research, though rt has added nun1erous species to existinO' and extinct genera, and has made the intervals betwee~ some few groups less wide than t~ey otherwise would have been, yet has done scarce~y anythrng in breaking down the distinction between spe~Ies, by ~onnecting them together by numerous, fine, r~termediate varieties · and this not having· been effected, rs probably the grav~st and most obvi~us .of all ~he many obje.ctio~s which may be urged agarnst my VI~ws. Hence rt Will be worth while to sum up the foregorng remarks, under an imaginary illustration. The Malay Achipelago is of about the size of Europe from the North Cape to the Mediterranean and from Britain to Ruesia ; and therefore equals all the geological formations which may have b.een examined with any accuracy, excepti~g those of the .united States of America. I fully agree with Mr. Godwrn-Austen, that the present condi~ion of the Malay Arch~pelago, \vith its numerous large Islands separated by Wide and shallow seas, probably represents the former state of Europe, when most of our formations were accumulating. The Malay Archipelago is one of the richest regions of the whole world in organic beings ; yet if all the species were to be collected which have ever lived there, how imperfectly would they represent the natural history of the world! But we have every reason to believe that the terrestrial productions of the archipelago would be prese~ved in an excessively imperfect manner in the formatwns which we suppose to be there accumulating. I suspect that not many of the strictly littoral animals, or of those which lived on naked submarine rocks, would be embedded · and those embedded in gravel or sand, would not end~re to · a distant epoch. Wherever sediment did not accumulate on the bed of the sea, or where it did not accumulate at a sufficient rate to protect organic bodies from decay, no remains could be preserved. CBAP. IX.] GEOLOGICAL RECORD. 263 . In our archipelago, I believe that fossiliferous formations could be formed of sufficient thickness to 1 t t ~ge, as d I·S t ant I· n f utur;· ty as t~e secondary formaatsi onos laine rn ~he past, o~ly during perrods of subsidence. These periods of sub~1dence would_ be separated from each other b1 enorm?us Interv~l~, durrng which the area would be mther ~tatlonary or nsrng; whilst rising, each fossiliferous formation would be destroyed almost as soon as a I at ed , b y the I· ncessant coast-ac' tion as we now see cocnu mthu - shores of South America. During the periods of subsi~ den?e there wo':lld probably be much extinction of life . dur~ng the periods of elevation, there would be much variation, but the geological record would then b 1 t perfect. e eas It ma:y be doub~ed whether the duration of any one grea~ period of subsidence over the whole or part of the a.rchipelag?, together with a contemporaneous accumulatiOn of sed~ment, would exceed the average duration of the same spemfic forms ; and these contingencies are indis~ ensable for the preservation of all the transitional gradat~ ons between any two or more species. If such gradatwns were not fully preserved, transitional varieties would merely appear as so many distinct species. It is, also probable that each. gre!1t period of subsidence would b~ Interrupted by osmllati~ns of level, and that slight clima~ al change.s would rntervene during such len th pelwds; and In these cases the inhabitants of the af.chl pe ag3 ~.ouhld. have ~o migrate, and no closely consecutive reco; o t. eir modifications could be preserved in any one 10rmatron. l · Very many of the marine inhabitants of the archipeago now range thousands of miles beyond its confines · :hd a~alogy l~ads me ~o believe that it would be chiefly ese a:-r~ngrng species which would oftenest produce b"e1 varieties; and the varieties would at first generally d:ec i' dcd ordconfined to one place, but if possessed of any e a vantage, or when further modified and im-p oved£ they would slowly spread and supplant their iar~ntt ohms. When such varieties returned to their nCien omes, as they would differ from their former |