darwin and modern science-第6节

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rck　out　of　court。　　How　was　it　that　Darwin　succeeded　where　others　had　failed？　　Because；　in　the　first　place；　he　had　clear　visions〃pensees　de　la　jeunesse；　executees　par　l'age　mur〃which　a　University　curriculum　had　not　made　impossible；　which　the　〃Beagle〃　voyage　made　vivid；　which　an　unrivalled　British　doggedness　made　realvisions　of　the　web　of　life；　of　the　fountain　of　change　within　the　organism；　of　the　struggle　for　existence　and　its　winnowing；　and　of　the　spreading　genealogical　tree。　　Because；　in　the　second　place；　he　put　so　much　grit　into　the　verification　of　his　visions；　putting　them　to　the　proof　in　an　argument　which　is　of　its　kinddirect　demonstration　being　out　of　the　questionquite　unequalled。　　Because；　in　the　third　place；　he　broke　down　the　opposition　which　the　most　scientific　had　felt　to　the　seductive　modal　formula　of　evolution　by　bringing　forward　a　more　plausible　theory　of　the　process　than　had　been　previously　suggested。　　Nor　can　one　forget；　since　questions　of　this　magnitude　are　human　and　not　merely　academic；　that　he　wrote　so　that　all　men　could　understand。

AS　REGARDS　THE　FACTORS　OF　EVOLUTION。

It　is　admitted　by　all　who　are　acquainted　with　the　history　of　biology　that　the　general　idea　of　organic　evolution　as　expressed　in　the　Doctrine　of　Descent　was　quite　familiar　to　Darwin's　grandfather；　and　to　others　before　and　after　him；　as　we　have　briefly　indicated。　　It　must　also　be　admitted　that　some　of　these　pioneers　of　evolutionism　did　more　than　apply　the　evolution…　idea　as　a　modal　formula　of　becoming；　they　began　to　inquire　into　the　factors　in　the　process。　　Thus　there　were　pre…Darwinian　theories　of　evolution；　and　to　these　we　must　now　briefly　refer。　　（See　Prof。　W。A。　Locy's　〃Biology　and　its　Makers〃。　　New　York；　1908。　　Part　II。　　〃The　Doctrine　of　Organic　Evolution〃。

In　all　biological　thinking　we　have　to　work　with　the　categories　Organism　FunctionEnvironment；　and　theories　of　evolution　may　be　classified　in　relation　to　these。　　To　some　it　has　always　seemed　that　the　fundamental　fact　is　the　living　organism；a　creative　agent；　a　striving　will；　a　changeful　Proteus；　selecting　its　environment；　adjusting　itself　to　it；　self…　differentiating　and　self…adaptive。　　The　necessity　of　recognising　the　importance　of　the　organism　is　admitted　by　all　Darwinians　who　start　with　inborn　variations；　but　it　is　open　to　question　whether　the　whole　truth　of　what　we　might　call　the　Goethian　position　is　exhausted　in　the　postulate　of　inherent　variability。

To　others　it　has　always　seemed　that　the　emphasis　should　be　laid　on　Function；on　use　and　disuse；　on　doing　and　not　doing。　　Practice　makes　perfect；　c'est　a　force　de　forger　qu'on　devient　forgeron。　　This　is　one　of　the　fundamental　ideas　of　Lamarckism；　to　some　extent　it　met　with　Darwin's　approval；　and　it　finds　many　supporters　to…day。　　One　of　the　ablest　of　these　Mr　Francis　Darwinhas　recently　given　strong　reasons　for　combining　a　modernised　Lamarckism　with　what　we　usually　regard　as　sound　Darwinism。　　（Presidential　Address　to　the　British　Association　meeting　at　Dublin　in　1908。）

To　others　it　has　always　seemed　that　the　emphasis　should　be　laid　on　the　Environment；　which　wakes　the　organism　to　action；　prompts　it　to　change；　makes　dints　upon　it；　moulds　it；　prunes　it；　and　finally；　perhaps；　kills　it。　It　is　again　impossible　to　doubt　that　there　is　truth　in　this　view；　for　even　if　environmentally　induced　〃modifications〃　be　not　transmissible；　environmentally　induced　〃variations〃　are；　and　even　if　the　direct　influence　of　the　environment　be　less　important　than　many　enthusiastic　supporters　of　this　viewmay　we　call　them　Buffoniansthink；　there　remains　the　indirect　influence　which　Darwinians　in　part　rely　on；the　eliminative　process。　　Even　if　the　extreme　view　be　held　that　the　only　form　of　discriminate　elimination　that　counts　is　inter…organismal　competition；　this　might　be　included　under　the　rubric　of　the　animate　environment。

In　many　passages　Buffon　（See　in　particular　Samuel　Butler；　〃Evolution　Old　and　New〃；　London；　1879；　J。L。　de　Lanessan；　〃Buffon　et　Darwin〃；　〃Revue　Scientifique〃；　XLIII。　pages　385…391；　425…432；　1889。）　definitely　suggested　that　environmental　influencesespecially　of　climate　and　foodwere　directly　productive　of　changes　in　organisms；　but　he　did　not　discuss　the　question　of　the　transmissibility　of　the　modifications　so　induced；　and　it　is　difficult　to　gather　from　his　inconsistent　writings　what　extent　of　transformation　he　really　believed　in。　　Prof。　Osborn　says　of　Buffon：　　〃The　struggle　for　existence；　the　elimination　of　the　least…perfected　species；　the　contest　between　the　fecundity　of　certain　species　and　their　constant　destruction；　are　all　clearly　expressed　in　various　passages。〃　　He　quotes　two　of　these　（op。　cit。　page　136。）：

〃Le　cours　ordinaire　de　la　nature　vivante；　est　en　general　toujours　constant；　toujours　le　meme；　son　mouvement；　toujours　regulier；　roule　sur　deux　points　inebranlables：　l'un；　la　fecondite　sans　bornes　donnee　a　toutes　les　especes；　l'autre；　les　obstacles　sans　nombre　qui　reduisent　cette　fecondite　a　une　mesure　determinee　et　ne　laissent　en　tout　temps　qu'a　peu　pres　la　meme　quantite　d'individus　de　chaque　espece〃。。。〃Les　especes　les　moins　parfaites；　les　plus　delicates；　les　plus　pesantes；　les　moins　agissantes；　les　moins　armees；　etc。；　ont　deja　disparu　ou　disparaitront。〃

Erasmus　Darwin　（See　Ernst　Krause　and　Charles　Darwin；　〃Erasmus　Darwin〃；　London；　1879。）　had　a　firm　grip　of　the　〃idea　of　the　gradual　formation　and　improvement　of　the　Animal　world；〃　and　he　had　his　theory　of　the　process。　　No　sentence　is　more　characteristic　than　this：　　〃All　animals　undergo　transformations　which　are　in　part　produced　by　their　own　exertions；　in　response　to　pleasures　and　pains；　and　many　of　these　acquired　forms　or　propensities　are　transmitted　to　their　posterity。〃　　This　is　Lamarckism　before　Lamarck；　as　his　grandson　pointed　out。　　His　central　idea　is　that　wants　stimulate　efforts　and　that　these　result　in　improvements；　which　subsequent　generations　make　better　still。　　He　realised　something　of　the　struggle　for　existence　and　even　pointed　out　that　this　advantageously　checks　the　rapid　multiplication。　　〃As　Dr　Krause　points　out；　Darwin　just　misses　the　connection　between　this　struggle　and　the　Survival　of　the　Fittest。〃　　（Osborn　op。　cit。　page　142。）

Lamarck　（1744…1829）　（See　E。　Perrier　〃La　Philosophie　Zoologique　avant　Darwin〃；　Paris；　1884；　A。　de　Quatrefages；　〃Darwin　et　ses　Precurseurs　Francais〃；　Paris；　1870；　Packard　op。　cit。；　also　Claus；　〃Lamarck　als　Begrunder　der　Descendenzlehre〃；　Wien；　1888；　Haeckel；　〃Natural　History　of　Creation〃；　English　translation　London；　1879；　Lang　〃Zur　Charakteristik　der　Forschungswege　von　Lamarck　und　Darwin〃；　Jena；　1889。）　seems　to　have　thought　out　his　theory　of　evolution　without　any　knowledge　of　Erasmus　Darwin's　which　it　closely　resembled。　　The　central　idea　of　his　theory　was　the　cumulative　inheritance　of　functional　modifications。　　〃Changes　in　environment　bring　about　changes　in　the　habits　of　animals。　　Changes　in　their　wants　necessarily　bring　about　parallel　changes　in　their　habits。　　If　new　wants　become　constant　or　very　lasting；　they　form　new　habits；　the　new　habits　involve　the　use　of　new　parts；　or　a　different　use　of　old　parts；　which　results　finally　in　the　production　of　new　organs　and　the　modification　of　old　ones。〃　　He　differed　from　Buffon　in　not　attaching　importance；　as　far　as　animals　are　concerned；　to　the　direct　influence　of　the　environment；　〃for　environment　can　effect　no　direct　change　whatever　upon　the　organisation　of　animals；〃　but　in　regard　to　plants　he　agreed　with　Buffon　that　external　conditions　directly　moulded　them。

Treviranus　（1776…1837）　（See　Huxley's　article　〃Evolution　in　Biology〃；　〃Encyclopaedia　Britannica〃　（9th　edit。）；　1878；　pages　744…751；　and　Sully's　article；　〃Evolution　in　Philosophy〃；　ibid。　pages　751…772。）；　whom　Huxley　ranked　beside　Lamarck；　was　on　the　whole　Buffonian；　attaching　chief　importance　to　the　influence　of　a　changeful　environment　both　in　modifying　and　in　eliminating；　but　he　was　also　Goethian；　for　instance　in　his　idea　that　species　like　individuals　pass　through　periods　of　growth；　full　bloom；　and　decline。　　〃Thus；　it　is　not　only　the　great　catastrophes　of　Nature　which　have　caused　extinction；　but　the　completion　of　cycles　of　existence；　out　of　which　new　cycles　have　begun。〃　　A　characteristic　sentence　is　quoted　by　Prof。　Osborn：　　〃In　every　living　being　there　exists　a　capability　of　an　endless　variety　of　form…assumption；　each　possesses　the　power　to　adapt　its　organisation　to　the　changes　of　the　outer　world；　and　it　is　this　power；　put　into　action　by　the　change　of　the　universe；　that　has　raised　the　simple　zoophytes　of　the　primitive　world　to　continually　higher　stages　of　organisation；　and　has　introduced　a　countless　variety　of　species　into　animate　Nature。〃

Goethe　（1749…1832）　（See　Haeckel；　〃Die　Naturanschauung　von　Darwin；　Goethe　und　Lamarck〃；　Jena；　1882。）；　who　knew　Buffon's　work　but　not　Lamarck's；　is　peculiarly　interesting　as　one　of　the　first　to　use　the　evolution…idea　as　a　guiding　hypothesis；　e。g。　in　the　interpretation　of　vestigial　structures　in　man；　and　to　realise　that　organisms　express　an　attempt　to　make　a　compromise　between　specific　inertia　and　individual　change。　　He　gave　the　finest　expression　that　science　has　yet　knownif　it　has　known　itof　the　kernel…　idea　of　what　is　called　〃bathmism；〃　the　idea　of　an　〃inherent　growth…force〃　and　at　the　same　time　he　held　that　〃the　way　of　life　p