a history of science-4-第26节

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e　other　parts。　　In　retrograde　fashion　nature　often　produces　cases　where　the　style　and　stigma　（Narben）　become　retransformed　into　petalsthat　is；　the　Ranunculus　Asiaticus　becomes　double　by　transforming　the　stigma　and　style　of　the　fruit…receptacle　into　real　petals；　while　the　stamens　are　often　found　unchanged　immediately　behind　the　corolla。

〃In　the　seed　receptacles；　in　spite　of　their　formation；　of　their　special　object；　and　of　their　method　of　being　joined　together；　we　cannot　fail　to　recognize　the　leaf　form。　　Thus；　for　instance；　the　pod　would　be　a　simple　leaf　folded　and　grown　together　on　its　margin；　the　siliqua　would　consist　of　more　leaves　folded　over　another；　the　compound　receptacles　would　be　explained　as　being　several　leaves　which；　being　united　above　one　centre；　keep　their　inward　parts　separate　and　are　joined　on　their　margins。　We　can　convince　ourselves　of　this　by　actual　sight　when　such　composite　capsules　fall　apart　after　becoming　ripe；　because　then　every　part　displays　an　opened　pod。〃＇1＇


The　theory　thus　elaborated　of　the　metamorphosis　of　parts　was　presently　given　greater　generality　through　extension　to　the　animal　kingdom；　in　the　doctrine　which　Goethe　and　Oken　advanced　independently；　that　the　vertebrate　skull　is　essentially　a　modified　and　developed　vertebra。　These　were　conceptions　worthy　of　a　poetimpossible；　indeed；　for　any　mind　that　had　not　the　poetic　faculty　of　correlation。　　But　in　this　case　the　poet's　vision　was　prophetic　of　a　future　view　of　the　most　prosaic　science。　The　doctrine　of　metamorphosis　of　parts　soon　came　to　be　regarded　as　of　fundamental　importance。

But　the　doctrine　had　implications　that　few　of　its　early　advocates　realized。　If　all　the　parts　of　a　flowersepal；　petal；　stamen；　pistil；　with　their　countless　deviations　of　contour　and　colorare　but　modifications　of　the　leaf；　such　modification　implies　a　marvellous　differentiation　and　development。　To　assert　that　a　stamen　is　a　metamorphosed　leaf　means；　if　it　means　anything；　that　in　the　long　sweep　of　time　the　leaf　has　by　slow　or　sudden　gradations　changed　its　character　through　successive　generations；　until　the　offspring；　so　to　speak；　of　a　true　leaf　has　become　a　stamen。　　But　if　such　a　metamorphosis　as　this　is　possibleif　the　seemingly　wide　gap　between　leaf　and　stamen　may　be　spanned　by　the　modification　of　a　line　of　organismswhere　does　the　possibility　of　modification　of　organic　type　find　its　bounds？　　Why　may　not　the　modification　of　parts　go　on　along　devious　lines　until　the　remote　descendants　of　an　organism　are　utterly　unlike　that　organism？　　Why　may　we　not　thus　account　for　the　development　of　various　species　of　beings　all　sprung　from　one　parent　stock？　　That；　too；　is　a　poet's　dream；　but　is　it　only　a　dream？　Goethe　thought　not。　　Out　of　his　studies　of　metamorphosis　of　parts　there　grew　in　his　mind　the　belief　that　the　multitudinous　species　of　plants　and　animals　about　us　have　been　evolved　from　fewer　and　fewer　earlier　parent　types；　like　twigs　of　a　giant　tree　drawing　their　nurture　from　the　same　primal　root。　It　was　a　bold　and　revolutionary　thought；　and　the　world　regarded　it　as　but　the　vagary　of　a　poet。


ERASMUS　DARWIN

Just　at　the　time　when　this　thought　was　taking　form　in　Goethe's　brain；　the　same　idea　was　germinating　in　the　mind　of　another　philosopher；　an　Englishman　of　international　fame；　Dr。　Erasmus　Darwin；　who；　while　he　lived；　enjoyed　the　widest　popularity　as　a　poet；　the　rhymed　couplets　of　his　Botanic　Garden　being　quoted　everywhere　with　admiration。　And　posterity　repudiating　the　verse　which　makes　the　body　of　the　book；　yet　grants　permanent　value　to　the　book　itself；　because；　forsooth；　its　copious　explanatory　foot…notes　furnish　an　outline　of　the　status　of　almost　every　department　of　science　of　the　time。

But　even　though　he　lacked　the　highest　art　of　the　versifier；　Darwin　had；　beyond　peradventure；　the　imagination　of　a　poet　coupled　with　profound　scientific　knowledge；　and　it　was　his　poetic　insight；　correlating　organisms　seemingly　diverse　in　structure　and　imbuing　the　lowliest　flower　with　a　vital　personality；　which　led　him　to　suspect　that　there　are　no　lines　of　demarcation　in　nature。　〃Can　it　be；〃　he　queries；　〃that　one　form　of　organism　has　developed　from　another；　that　different　species　are　really　but　modified　descendants　of　one　parent　stock？〃　　The　alluring　thought　nestled　in　his　mind　and　was　nurtured　there；　and　grew　in　a　fixed　belief；　which　was　given　fuller　expression　in　his　Zoonomia　and　in　the　posthumous　Temple　of　Nature。

Here　is　his　rendering　of　the　idea　as　versified　in　the　Temple　of　Nature：

　〃Organic　life　beneath　the　shoreless　waves　　　Was　born；　and　nursed　in　Ocean's　pearly　caves；　　　First　forms　minute；　unseen　by　spheric　glass；　　　Move　on　the　mud；　or　pierce　the　watery　mass；　　　These；　as　successive　generations　bloom；　　　New　powers　acquire　and　larger　limbs　assume；　　　Whence　countless　groups　of　vegetation　spring；　　　And　breathing　realms　of　fin；　and　feet；　and　wing。

　〃Thus　the　tall　Oak；　the　giant　of　the　wood；　　　Which　bears　Britannia's　thunders　on　the　flood；　　　The　Whale；　unmeasured　monster　of　the　main；　　　The　lordly　lion；　monarch　of　the　plain；　　　The　eagle；　soaring　in　the　realms　of　air；　　　Whose　eye；　undazzled；　drinks　the　solar　glare；　　　Imperious　man；　who　rules　the　bestial　crowd；　　　Of　language；　reason；　and　reflection　proud；　　　With　brow　erect；　who　scorns　this　earthy　sod；　　　And　styles　himself　the　image　of　his　God　　　Arose　from　rudiments　of　form　and　sense；　　　An　embryon　point　or　microscopic　ens！〃＇2＇


Here；　clearly　enough；　is　the　idea　of　evolution。　　But　in　that　day　there　was　little　proof　forthcoming　of　its　validity　that　could　satisfy　any　one　but　a　poet；　and　when　Erasmus　Darwin　died；　in　1802；　the　idea　of　transmutation　of　species　was　still　but　an　unsubstantiated　dream。

It　was　a　dream；　however；　which　was　not　confined　to　Goethe　and　Darwin。　Even　earlier　the　idea　had　come　more　or　less　vaguely　to　another　great　dreamerand　workerof　Germany；　Immanuel　Kant；　and　to　several　great　Frenchmen；　including　De　Maillet；　Maupertuis；　Robinet；　and　the　famous　naturalist　Buffona　man　who　had　the　imagination　of　a　poet；　though　his　message　was　couched　in　most　artistic　prose。　　Not　long　after　the　middle　of　the　eighteenth　century　Buffon　had　put　forward　the　idea　of　transmutation　of　species；　and　he　reiterated　it　from　time　to　time　from　then　on　till　his　death　in　1788。　But　the　time　was　not　yet　ripe　for　the　idea　of　transmutation　of　species　to　burst　its　bonds。

And　yet　this　idea；　in　a　modified　or　undeveloped　form；　had　taken　strange　hold　upon　the　generation　that　was　upon　the　scene　at　the　close　of　the　eighteenth　century。　Vast　numbers　of　hitherto　unknown　species　of　animals　had　been　recently　discovered　in　previously　unexplored　regions　of　the　globe；　and　the　wise　men　were　sorely　puzzled　to　account　for　the　disposal　of　all　of　these　at　the　time　of　the　deluge。　　It　simplified　matters　greatly　to　suppose　that　many　existing　species　had　been　developed　since　the　episode　of　the　ark　by　modification　of　the　original　pairs。　The　remoter　bearings　of　such　a　theory　were　overlooked　for　the　time；　and　the　idea　that　American　animals　and　birds；　for　example；　were　modified　descendants　of　Old…World　formsthe　jaguar　of　the　leopard；　the　puma　of　the　lion；　and　so　onbecame　a　current　belief　with　that　class　of　humanity　who　accept　almost　any　statement　as　true　that　harmonizes　with　their　prejudices　without　realizing　its　implications。

Thus　it　is　recorded　with　eclat　that　the　discovery　of　the　close　proximity　of　America　at　the　northwest　with　Asia　removes　all　difficulties　as　to　the　origin　of　the　Occidental　faunas　and　floras；　since　Oriental　species　might　easily　have　found　their　way　to　America　on　the　ice；　and　have　been　modified　as　we　find　them　by　〃the　well…known　influence　of　climate。〃　And　the　persons　who　gave　expression　to　this　idea　never　dreamed　of　its　real　significance。　　In　truth；　here　was　the　doctrine　of　evolution　in　a　nutshell；　and；　because　its　ultimate　bearings　were　not　clear；　it　seemed　the　most　natural　of　doctrines。　　But　most　of　the　persons　who　advanced　it　would　have　turned　from　it　aghast　could　they　have　realized　its　import。　As　it　was；　however；　only　here　and　there　a　man　like　Buffon　reasoned　far　enough　to　inquire　what　might　be　the　limits　of　such　assumed　transmutation；　and　only　here　and　there　a　Darwin　or　a　Goethe　reached　the　conviction　that　there　are　no　limits。


LAMARCK　VERSUS　CUVIER

And　even　Goethe　and　Darwin　had　scarcely　passed　beyond　that　tentative　stage　of　conviction　in　which　they　held　the　thought　of　transmutation　of　species　as　an　ancillary　belief　not　ready　for　full　exposition。　There　was　one　of　their　contemporaries；　however；　who；　holding　the　same　conception；　was　moved　to　give　it　full　explication。　This　was　the　friend　and　disciple　of　Buffon；　Jean　Baptiste　de　Lamarck。　　Possessed　of　the　spirit　of　a　poet　and　philosopher；　this　great　Frenchman　had　also　the　widest　range　of　technical　knowledge；　covering　the　entire　field　of　animate　nature。　　The　first　half　of　his　long　life　was　devoted　chiefly　to　botany；　in　which　he　attained　high　distinction。　　Then；　just　at　the　beginning　of　the　nineteenth　century；　he　turned　to　zoology；　in　particular　to　the　lower　forms　of　animal　life。　Studying　these　lowly　organisms；　existing　and　fossil；　he　was　more　and　more　impressed　with　the　gradations　of　form　everywhere　to　be　seen；　the　linking　of　diverse　families　through　intermediate　ones；　and　in　particular　with　the　pred