darwin and modern science-第109节

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m　to　consider　theories　with　regard　to　the　introduction　of　new　species；　and；　rejecting　the　fanciful　notions　of　〃centres　or　foci　of　creation；〃　he　argues　strongly　in　favour　of　the　view；　as　most　reconcileable　with　observed　facts；　that　〃each　species　may　have　had　its　origin　in　a　single　pair；　or　individual；　where　an　individual　was　sufficient；　and　species　may　have　been　created　in　succession　at　such　times　and　in　such　places　as　to　enable　them　to　multiply　and　endure　for　an　appointed　period；　and　occupy　an　appointed　space　on　the　globe。〃　　（〃Principles　of　Geology〃；　Vol。　II。　（1st　edition　1832）；　page　124。　　We　now　know；　as　has　been　so　well　pointed　out　by　Huxley；　that　Lyell；　as　early　as　1827；　was　prepared　to　accept　the　doctrine　of　the　transmutation　of　species。　　In　that　year　he　wrote　to　Mantell；　〃What　changes　species　may　really　undergo！　　How　impossible　will　it　be　to　distinguish　and　lay　down　a　line；　beyond　which　some　of　the　so…called　extinct　species　may　have　never　passed　into　recent　ones〃　（Lyell's　〃Life　and　Letters〃　Vol。　I。　page　168）。　　To　Sir　John　Herschel　in　1836；　he　wrote；　〃In　regard　to　the　origination　of　new　species；　I　am　very　glad　to　find　that　you　think　it　probable　that　it　may　be　carried　on　through　the　intervention　of　intermediate　causes。　　I　left　this　rather　to　be　inferred；　not　thinking　it　worth　while　to　offend　a　certain　class　of　persons　by　embodying　in　words　what　would　only　be　a　speculation〃　（Ibid。　page　467）。　　He　expressed　the　same　views　to　Whewell　in　1837　（Ibid。　Vol。　II。　page　5。）；　and　to　Sedgwick　（Ibid。　Vol。　II。　page　36）　to　whom　he　says；　of　〃the　theory；　that　the　creation　of　new　species　is　going　on　at　the　present　day〃〃I　really　entertain　it；〃　but　〃I　have　studiously　avoided　laying　the　doctrine　down　dogmatically　as　capable　of　proof〃　（see　Huxley　in　〃L。L。〃　II。　pages　190…195。））

After　pointing　out　how　impossible　it　would　be　for　a　naturalist　to　prove　that　a　newly　DISCOVERED　species　was　really　newly　CREATED　（Mr　F。　Darwin　has　pointed　out　that　his　father　（like　Lyell）　often　used　the　term　〃Creation〃　in　speaking　of　the　origin　of　new　species　（〃L。L。〃　II。　chapter　1。））；　Lyell　argued　that　no　satisfactory　evidence　OF　THE　WAY　in　which　these　new　forms　were　created；　had　as　yet　been　discovered；　but　that　he　entertained　the　hope　of　a　possible　solution　of　the　problem　being　found　in　the　study　of　the　geological　record。

It　is　not　difficult；　in　reading　these　chapters　of　Lyell's　great　work；　to　realise　what　an　effect　they　would　have　on　the　mind　of　Darwin；　as　new　facts　were　collected　and　fresh　observations　concerning　extinct　and　recent　forms　were　made　in　his　travels。　　We　are　not　surprised　to　find　him　writing　home；　〃I　am　become　a　zealous　disciple　of　Mr　Lyell's　views；　as　known　in　his　admirable　book。　　Geologising　in　South　America；　I　am　tempted　to　carry　parts　to　a　greater　extent　even　than　he　does。〃　　（〃L。L。〃　I。　page　263。）

Lyell's　anticipation　that　the　study　of　the　geological　record　might　afford　a　clue　to　the　discovery　of　how　new　species　originate　was　remarkably　fulfilled；　within　a　few　months；　by　Darwin's　discovery　of　fossil　bones　in　the　red　Pampean　mud。

It　is　very　true　that；　as　Huxley　remarked；　Darwin's　knowledge　of　comparative　anatomy　must　have　been；　at　that　time；　slight；　but　that　he　recognised　the　remarkable　resemblances　between　the　extinct　and　existing　mammals　of　South　America　is　proved　beyond　all　question　by　a　passage　in　his　letter　to　Henslow；　written　November　24th；　1832：　　〃I　have　been　very　lucky　with　fossil　bones；　I　have　fragments　of　at　least　six　distinct　animals。。。I　found　a　large　surface　of　osseous　polygonal　plates。。。Immediately　I　saw　them　I　thought　they　must　belong　to　an　enormous　armadillo；　living　species　of　which　genus　are　so　abundant　here；〃　and　he　goes　on　to　say　that　he　has　〃the　lower　jaw　of　some　large　animal　which；　from　the　molar　teeth；　I　should　think　belonged　to　the　Edentata。〃　　（〃M。L。〃　I。　pages　11；　12。　　See　〃Extracts　of　Letters　addressed　to　Prof。　Henslow　by　C。　Darwin〃　（1835）；　page　7。）

Having　found　this　important　clue；　Darwin　followed　it　up　with　characteristic　perseverance。　　In　his　quest　for　more　fossil　bones　he　was　indefatigable。　　Mr　Francis　Darwin　tells　us；　〃I　have　often　heard　him　speak　of　the　despair　with　which　he　had　to　break　off　the　projecting　extremity　of　a　huge；　partly　excavated　bone；　when　the　boat　waiting　for　him　would　wait　no　longer。〃　　（〃L。L。〃　I。　page　276　（footnote）。）　　Writing　to　Haeckel　in　1864；　Darwin　says：　　〃I　shall　never　forget　my　astonishment　when　I　dug　out　a　gigantic　piece　of　armour；　like　that　of　the　living　armadillo。〃　　（Haeckel；　〃History　of　Creation〃；　Vol。　I。　page　134；　London；　1876。）

In　a　letter　to　Henslow　in　1834　Darwin　says：　　〃I　have　just　got　scent　of　some　fossil　bones。。。what　they　may　be　I　do　not　know；　but　if　gold　or　galloping　will　get　them　they　shall　be　mine。〃　　（〃M。L。〃　I。　page　15。）

Darwin　also　showed　his　sense　of　the　importance　of　the　discovery　of　these　bones　by　his　solicitude　about　their　safe　arrival　and　custody。　　From　the　Falkland　Isles　（March；　1834）；　he　writes　to　Henslow：　　〃I　have　been　alarmed　by　your　expression　'cleaning　all　the　bones'　as　I　am　afraid　the　printed　numbers　will　be　lost：　　the　reason　I　am　so　anxious　they　should　not　be；　is；　that　a　part　were　found　in　a　gravel　with　recent　shells；　but　others　in　a　very　different　bed。　　Now　with　these　latter　there　were　bones　of　an　Agouti；　a　genus　of　animals；　I　believe；　peculiar　to　America；　and　it　would　be　curious　to　prove　that　some　one　of　the　genus　co…existed　with　the　Megatherium：　　such　and　many　other　points　depend　on　the　numbers　being　carefully　preserved。〃　　（〃Extracts　from　Letters　etc。〃；　pages　13…14。）　　In　the　abstract　of　the　notes　read　to　the　Geological　Society　in　1835；　we　read：　　〃In　the　gravel　of　Patagonia　he　（Darwin）　also　found　many　bones　of　the　Megatherium　and　of　five　or　six　other　species　of　quadrupeds；　among　which　he　has　detected　the　bones　of　a　species　of　Agouti。　　He　also　met　with　several　examples　of　the　polygonal　plates；　etc。〃　　（〃Proc。　Geol。　Soc。〃　Vol。　II。　pages　211…212。）

Darwin's　own　recollections　entirely　bear　out　the　conclusion　that　he　fully　recognised；　WHILE　IN　SOUTH　AMERICA；　the　wonderful　significance　of　the　resemblances　between　the　extinct　and　recent　mammalian　faunas。　　He　wrote　in　his　〃Autobiography〃：　　〃During　the　voyage　of　the　'Beagle'　I　had　been　deeply　impressed　by　discovering　in　the　Pampean　formation　great　fossil　animals　covered　with　armour　like　that　on　the　existing　armadillos。〃　　（〃L。L。〃　I。　page　82。）

The　impression　made　on　Darwin's　mind　by　the　discovery　of　these　fossil　bones；　was　doubtless　deepened　as；　in　his　progress　southward　from　Brazil　to　Patagonia；　he　found　similar　species　of　Edentate　animals　everywhere　replacing　one　another　among　the　living　forms；　while；　whenever　fossils　occurred；　they　also　were　seen　to　belong　to　the　same　remarkable　group　of　animals。　　（While　Darwin　was　making　these　observations　in　South　America；　a　similar　generalisation　to　that　at　which　he　arrived　was　being　reached；　quite　independently　and　almost　simultaneously；　with　respect　to　the　fossil　and　recent　mammals　of　Australia。　　In　the　year　1831；　Clift　gave　to　Jameson　a　list　of　bones　occurring　in　the　caves　and　breccias　of　Australia；　and　in　publishing　this　list　the　latter　referred　to　the　fact　that　the　forms　belonged　to　marsupials；　similar　to　those　of　the　existing　Australian　fauna。　　But　he　also　stated　that；　as　a　skull　had　been　identified　（doubtless　erroneously）　as　having　belonged　to　a　hippopotamus；　other　mammals　than　marsupials　must　have　spread　over　the　island　in　late　Tertiary　times。　　It　is　not　necessary　to　point　out　that　this　paper　was　quite　unknown　to　Darwin　while　in　South　America。　　Lyell　first　noticed　it　in　the　third　edition　of　his　〃Principles〃；　which　was　published　in　May；　1834　（see　〃Edinb。　New　Phil。　Journ。〃　Vol。　X。　（1831）；　pages　394…6；　and　Lyell's　〃Principles〃　（3rd　edition）；　Vol。　III。　page　421）。　　Darwin　referred　to　this　discovery　in　1839　（see　his　〃Journal〃；　page　210。）

That　the　passage　in　Darwin's　pocket…book　for　1837　can　only　refer　to　an　AWAKENING　of　Darwin's　interest　in　the　subjectprobably　resulting　from　a　sight　of　the　bones　when　they　were　being　unpackedI　think　there　cannot　be　the　smallest　doubt；　AND　WE　MAY　THEREFORE　CONFIDENTLY　FIX　UPON　NOVEMBER；　1832；　AS　THE　DATE　AT　WHICH　DARWIN　COMMENCED　THAT　LONG　SERIES　OF　OBSERVATIONS　AND　REASONINGS　WHICH　EVENTUALLY　CULMINATED　IN　THE　PREPARATION　OF　THE　〃ORIGIN　OF　SPECIES〃。　　Equally　certain　is　it；　that　it　was　his　geological　work　that　led　Darwin　into　those　paths　of　research　which　in　the　end　conducted　him　to　his　great　discoveries。　　I　quite　agree　with　the　view　expressed　by　Mr　F。　Darwin　and　Professor　Seward；　that　Darwin；　like　Lyell；　〃thought　it　'almost　useless'　to　try　to　prove　the　truth　of　evolution　until　the　cause　of　change　was　discovered〃　（〃M。L。〃　I。　page　38。）；　and　that　possibly　he　may　at　times　have　vacillated　in　his　opinions；　but　I　believe　there　is　evidence　that；　from　the　date　mentioned；　the　〃species　question〃　was　always　more　or　less　present　in　Darwin's　mind。　　（Although　we　admit　with　Huxley　that　Darwin's　training　in　comparative　anatomy　was　very　small；　yet　it　may　be　remembered　that　he　was　a　medical　student　for　two　years；　and；　if　he　hated　the　lectures；　he　enjoyed　the　society　of　naturalists。　　He　had　with　him　in　the　little　〃Beagle〃　library　a　fair　number　of　zoological　books；　including　works　on　Osteology　by　Cuvier；　Desmarest　and　Lesson；　as　well　as　two　French　Encyclopaedias　of　Nat