a history of science-4-第29节

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this　one　in　additionthat　whatever　is　left　from　the　domain　of　ignorance；　and　made　undoubted　matter　of　science；　forms　a　new　support　to　the　same　doctrine。　　The　opposite　view；　once　predominant；　has　been　shrinking　for　ages　into　lesser　space；　and　now　maintains　a　footing　only　in　a　few　departments　of　nature　which　happen　to　be　less　liable　than　others　to　a　clear　investigation。　The　chief　of　these；　if　not　almost　the　only　one；　is　the　origin　of　the　organic　kingdoms。　　So　long　as　this　remains　obscure；　the　supernatural　will　have　a　certain　hold　upon　enlightened　persons。　Should　it　ever　be　cleared　up　in　a　way　that　leaves　no　doubt　of　a　natural　origin　of　plants　and　animals；　there　must　be　a　complete　revolution　in　the　view　which　is　generally　taken　of　the　relation　of　the　Father　of　our　being。

〃This　prepares　the　way　for　a　few　remarks　on　the　present　state　of　opinion　with　regard　to　the　origin　of　organic　nature。　The　great　difficulty　here　is　the　apparent　determinateness　of　species。　These　forms　of　life　being　apparently　unchangeable；　or　at　least　always　showing　a　tendency　to　return　to　the　character　from　which　they　have　diverged；　the　idea　arises　that　there　can　have　been　no　progression　from　one　to　another；　each　must　have　taken　its　special　form；　independently　of　other　forms；　directly　from　the　appointment　of　the　Creator。　　The　Edinburgh　Review　writer　says；　'they　were　created　by　the　hand　of　God　and　adapted　to　the　conditions　of　the　period。'　Now　it　is；　in　the　first　place；　not　certain　that　species　constantly　maintain　a　fixed　character；　for　we　have　seen　that　what　were　long　considered　as　determinate　species　have　been　transmuted　into　others。　Passing；　however；　from　this　fact；　as　it　is　not　generally　received　among　men　of　science；　there　remain　some　great　difficulties　in　connection　with　the　idea　of　special　creation。　　First　we　should　have　to　suppose；　as　pointed　out　in　my　former　volume；　a　most　startling　diversity　of　plan　in　the　divine　workings；　a　great　general　plan　or　system　of　law　in　the　leading　events　of　world…making；　and　a　plan　of　minute；　nice　operation；　and　special　attention　in　some　of　the　mere　details　of　the　process。　The　discrepancy　between　the　two　conceptions　is　surely　overpowering；　when　we　allow　ourselves　to　see　the　whole　matter　in　a　steady　and　rational　light。　There　is；　also；　the　striking　fact　of　an　ascertained　historical　progress　of　plants　and　animals　in　the　order　of　their　organization；　marine　and　cellular　plants　and　invertebrated　animals　first；　afterwards　higher　examples　of　both。　　In　an　arbitrary　system　we　had　surely　no　reason　to　expect　mammals　after　reptiles；　yet　in　this　order　they　came。　The　writer　in　the　Edinburgh　Review　speaks　of　animals　as　coming　in　adaptation　to　conditions；　but　this　is　only　true　in　a　limited　sense。　The　groves　which　formed　the　coal…beds　might　have　been　a　fitting　habitation　for　reptiles；　birds；　and　mammals；　as　such　groves　are　at　the　present　day；　yet　we　see　none　of　the　last　of　these　classes　and　hardly　any　traces　of　the　two　first　at　that　period　of　the　earth。　　Where　the　iguanodon　lived　the　elephant　might　have　lived；　but　there　was　no　elephant　at　that　time。　The　sea　of　the　Lower　Silurian　era　was　capable　of　supporting　fish；　but　no　fish　existed。　　It　hence　forcibly　appears　that　theatres　of　life　must　have　remained　unserviceable；　or　in　the　possession　of　a　tenantry　inferior　to　what　might　have　enjoyed　them；　for　many　ages：　there　surely　would　have　been　no　such　waste　allowed　in　a　system　where　Omnipotence　was　working　upon　the　plan　of　minute　attention　to　specialities。　The　fact　seems　to　denote　that　the　actual　procedure　of　the　peopling　of　the　earth　was　one　of　a　natural　kind；　requiring　a　long　space　of　time　for　its　evolution。　　In　this　supposition　the　long　existence　of　land　without　land　animals；　and　more　particularly　without　the　noblest　classes　and　orders；　is　only　analogous　to　the　fact；　not　nearly　enough　present　to　the　minds　of　a　civilized　people；　that　to　this　day　the　bulk　of　the　earth　is　a　waste　as　far　as　man　is　concerned。

〃Another　startling　objection　is　in　the　infinite　local　variation　of　organic　forms。　　Did　the　vegetable　and　animal　kingdoms　consist　of　a　definite　number　of　species　adapted　to　peculiarities　of　soil　and　climate；　and　universally　distributed；　the　fact　would　be　in　harmony　with　the　idea　of　special　exertion。　　But　the　truth　is　that　various　regions　exhibit　variations　altogether　without　apparent　end　or　purpose。　　Professor　Henslow　enumerates　forty…five　distinct　flowers　or　sets　of　plants　upon　the　surface　of　the　earth；　notwithstanding　that　many　of　these　would　be　equally　suitable　elsewhere。　The　animals　of　different　continents　are　equally　various；　few　species　being　the　same　in　any　two；　though　the　general　character　may　conform。　The　inference　at　present　drawn　from　this　fact　is　that　there　must　have　been；　to　use　the　language　of　the　Rev。　Dr。　Pye　Smith；　'separate　and　original　creations；　perhaps　at　different　and　respectively　distinct　epochs。'　It　seems　hardly　conceivable　that　rational　men　should　give　an　adherence　to　such　a　doctrine　when　we　think　of　what　it　involves。　In　the　single　fact　that　it　necessitates　a　special　fiat　of　the　inconceivable　Author　of　this　sand…cloud　of　worlds　to　produce　the　flora　of　St。　Helena；　we　read　its　more　than　sufficient　condemnation。　It　surely　harmonizes　far　better　with　our　general　ideas　of　nature　to　suppose　that；　just　as　all　else　in　this　far…spread　science　was　formed　on　the　laws　impressed　upon　it　at　first　by　its　Author；　so　also　was　this。　An　exception　presented　to　us　in　such　a　light　appears　admissible　only　when　we　succeed　in　forbidding　our　minds　to　follow　out　those　reasoning　processes　to　which；　by　another　law　of　the　Almighty；　they　tend；　and　for　which　they　are　adapted。〃＇4＇


Such　reasoning　as　this　naturally　aroused　bitter　animadversions；　and　cannot　have　been　without　effect　in　creating　an　undercurrent　of　thought　in　opposition　to　the　main　trend　of　opinion　of　the　time。　But　the　book　can　hardly　be　said　to　have　done　more　than　that。　Indeed；　some　critics　have　denied　it　even　this　merit。　After　its　publication；　as　before；　the　conception　of　transmutation　of　species　remained　in　the　popular　estimation；　both　lay　and　scientific；　an　almost　forgotten　〃heresy。〃

It　is　true　that　here　and　there　a　scientist　of　greater　or　less　reputeas　Von　Buch；　Meckel；　and　Von　Baer　in　Germany；　Bory　Saint…Vincent　in　France；　Wells；　Grant；　and　Matthew　in　England；　and　Leidy　in　Americahad　expressed　more　or　less　tentative　dissent　from　the　doctrine　of　special　creation　and　immutability　of　species；　but　their　unaggressive　suggestions；　usually　put　forward　in　obscure　publications；　and　incidentally；　were　utterly　overlooked　and　ignored。　And　so；　despite　the　scientific　advances　along　many　lines　at　the　middle　of　the　century；　the　idea　of　the　transmutability　of　organic　races　had　no　such　prominence；　either　in　scientific　or　unscientific　circles；　as　it　had　acquired　fifty　years　before。　Special　creation　held　the　day；　seemingly　unopposed。


DARWIN　AND　THE　ORIGIN　OF　SPECIES

But　even　at　this　time　the　fancied　security　of　the　special…creation　hypothesis　was　by　no　means　real。　　Though　it　seemed　so　invincible；　its　real　position　was　that　of　an　apparently　impregnable　fortress　beneath　which；　all　unbeknown　to　the　garrison；　a　powder…mine　has　been　dug　and　lies　ready　for　explosion。　For　already　there　existed　in　the　secluded　work…room　of　an　English　naturalist；　a　manuscript　volume　and　a　portfolio　of　notes　which　might　have　sufficed；　if　given　publicity；　to　shatter　the　entire　structure　of　the　special…creation　hypothesis。　The　naturalist　who；　by　dint　of　long　and　patient　effort；　had　constructed　this　powder…mine　of　facts　was　Charles　Robert　Darwin；　grandson　of　the　author　of　Zoonomia。

As　long　ago　as　July　1；　1837；　young　Darwin；　then　twenty…eight　years　of　age；　had　opened　a　private　journal；　in　which　he　purposed　to　record　all　facts　that　came　to　him　which　seemed　to　have　any　bearing　on　the　moot　point　of　the　doctrine　of　transmutation　of　species。　　Four　or　five　years　earlier；　during　the　course　of　that　famous　trip　around　the　world　with　Admiral　Fitzroy；　as　naturalist　to　the　Beagle；　Darwin　had　made　the　personal　observations　which　first　tended　to　shake　his　belief　of　the　fixity　of　species。　In　South　America；　in　the　Pampean　formation；　he　had　discovered　〃great　fossil　animals　covered　with　armor　like　that　on　the　existing　armadillos；〃　and　had　been　struck　with　this　similarity　of　type　between　ancient　and　existing　faunas　of　the　same　region。　　He　was　also　greatly　impressed　by　the　manner　in　which　closely　related　species　of　animals　were　observed　to　replace　one　another　as　he　proceeded　southward　over　the　continent；　and　〃by　the　South…American　character　of　most　of　the　productions　of　the　Galapagos　Archipelago；　and　more　especially　by　the　manner　in　which　they　differ　slightly　on　each　island　of　the　group；　none　of　the　islands　appearing　to　be　very　ancient　in　a　geological　sense。〃

At　first　the　full　force　of　these　observations　did　not　strike　him；　for；　under　sway　of　Lyell's　geological　conceptions；　he　tentatively　explained　the　relative　absence　of　life　on　one　of　the　Galapagos　Islands　by　suggesting　that　perhaps　no　species　had　been　created　since　that　island　arose。　But　gradually　it　dawned　upon　him　that　such　facts　as　he　had　observed　〃could　only　be　explained　on　the　supposition　that　species　gradually　become　modified。〃　From　then　on；　as　he　afterwards　asserted；　the　subject　haunted　him