darwin and modern science-第46节

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ection　with　Lamarck's　idea　of　transformative　heredity；　and　applies　the　two　in　conjunction　to　the　facts　of　histology。　　He　lays　stress　on　the　significance　of　functional　adaptation；　which　I　had　described　in　1866；　under　the　head　of　cumulative　adaptation；　as　the　most　important　factor　in　evolution。　　Pointing　out　its　influence　in　the　cell…life　of　the　tissues；　he　puts　〃cellular　selection〃　above　〃personal　selection；〃　and　shows　how　the　finest　conceivable　adaptations　in　the　structure　of　the　tissue　may　be　brought　about　quite　mechanically；　without　preconceived　plan。　　This　〃mechanical　teleology〃　is　a　valuable　extension　of　Darwin's　monistic　principle　of　selection　to　the　whole　field　of　cellular　physiology　and　histology；　and　is　wholly　destructive　of　dualistic　vitalism。

The　most　important　advance　that　evolution　has　made　since　Darwin　and　the　most　valuable　amplification　of　his　theory　of　selection　is；　in　my　opinion；　the　work　of　Richard　Semon：　　〃Die　Mneme　als　erhaltendes　Prinzip　im　Wechsel　des　organischen　Geschehens〃　（Leipzig；　1904。）。　　He　offers　a　psychological　explanation　of　the　facts　of　heredity　by　reducing　them　to　a　process　of　（unconscious）　memory。　　The　physiologist　Ewald　Hering　had　shown　in　1870　that　memory　must　be　regarded　as　a　general　function　of　organic　matter；　and　that　we　are　quite　unable　to　explain　the　chief　vital　phenomena；　especially　those　of　reproduction　and　inheritance；　unless　we　admit　this　unconscious　memory。　In　my　essay　〃Die　Perigenesis　der　Plastidule〃　（Berlin；　1876。）　I　elaborated　this　far…reaching　idea；　and　applied　the　physical　principle　of　transmitted　motion　to　the　plastidules；　or　active　molecules　of　plasm。　　I　concluded　that　〃heredity　is　the　memory　of　the　plastidules；　and　variability　their　power　of　comprehension。〃　　This　〃provisional　attempt　to　give　a　mechanical　explanation　of　the　elementary　processes　of　evolution〃　I　afterwards　extended　by　showing　that　sensitiveness　is　（as　Carl　Nageli；　Ernst　Mach；　and　Albrecht　Rau　express　it）　a　general　quality　of　matter。　　This　form　of　panpsychism　finds　its　simplest　expression　in　the　〃trinity　of　substance。〃

To　the　two　fundamental　attributes　that　Spinoza　ascribed　to　substance　Extension　（matter　as　occupying　space）　and　Cogitation　（energy；　force）we　now　add　the　third　fundamental　quality　of　Psychoma　（sensitiveness；　soul）。　　I　further　elaborated　this　trinitarian　conception　of　substance　in　the　nineteenth　chapter　of　my　〃Die　Lebenswunder〃　（1904）　（〃Wonders　of　Life〃；　London；　1904。）；　and　it　seems　to　me　well　calculated　to　afford　a　monistic　solution　of　many　of　the　antitheses　of　philosophy。

This　important　Mneme…theory　of　Semon　and　the　luminous　physiological　experiments　and　observations　associated　with　it　not　only　throw　considerable　light　on　transformative　inheritance；　but　provide　a　sound　physiological　foundation　for　the　biogenetic　law。　　I　had　endeavoured　to　show　in　1874；　in　the　first　chapter　of　my　〃Anthropogenie〃　（English　translation；　〃The　Evolution　of　Man〃；　2　volumes；　London；　1879　and　1905。）；　that　this　fundamental　law　of　organic　evolution　holds　good　generally；　and　that　there　is　everywhere　a　direct　causal　connection　between　ontogeny　and　phylogeny。　　〃Phylogenesis　is　the　mechanical　cause　of　ontogenesis〃；　in　other　words；　〃The　evolution　of　the　stem　or　race　isin　accordance　with　the　laws　of　heredity　and　adaptationthe　real　cause　of　all　the　changes　that　appear；　in　a　condensed　form；　in　the　development　of　the　individual　organism　from　the　ovum；　in　either　the　embryo　or　the　larva。〃

It　is　now　fifty　years　since　Charles　Darwin　pointed　out；　in　the　thirteenth　chapter　of　his　epoch…making　〃Origin　of　Species〃；　the　fundamental　importance　of　embryology　in　connection　with　his　theory　of　descent：

〃The　leading　facts　in　embryology；　which　are　second　to　none　in　importance；　are　explained　on　the　principle　of　variations　in　the　many　descendants　from　some　one　ancient　progenitor；　having　appeared　at　a　not　very　early　period　of　life；　and　having　been　inherited　at　a　corresponding　period。〃　　（〃Origin　of　Species〃　（6th　edition）；　page　396。）

He　then　shows　that　the　striking　resemblance　of　the　embryos　and　larvae　of　closely　related　animals；　which　in　the　mature　stage　belong　to　widely　different　species　and　genera；　can　only　be　explained　by　their　descent　from　a　common　progenitor。　　Fritz　Muller　made　a　closer　study　of　these　important　phenomena　in　the　instructive　instance　of　the　Crustacean　larva；　as　given　in　his　able　work　〃Fur　Darwin〃　（1864）。　　（English　translation；　〃Facts　and　Arguments　for　Darwin〃；　London；　1869。）　　I　then；　in　1872；　extended　the　range　so　as　to　include　all　animals　（with　the　exception　of　the　unicellular　Protozoa）　and　showed；　by　means　of　the　theory　of　the　Gastraea；　that　all　multicellular；　tissue…forming　animalsall　the　Metazoadevelop　in　essentially　the　same　way　from　the　primary　germ…layers。　　I　conceived　the　embryonic　form；　in　which　the　whole　structure　consists　of　only　two　layers　of　cells；　and　is　known　as　the　gastrula；　to　be　the　ontogenetic　recapitulation；　maintained　by　tenacious　heredity；　of　a　primitive　common　progenitor　of　all　the　Metazoa；　the　Gastraea。　　At　a　later　date　（1895）　Monticelli　discovered　that　this　conjectural　ancestral　form　is　still　preserved　in　certain　primitive　CoelenterataPemmatodiscus；　Kunstleria；　and　the　nearly…related　Orthonectida。

The　general　application　of　the　biogenetic　law　to　all　classes　of　animals　and　plants　has　been　proved　in　my　〃Systematische　Phylogenie〃。　　（3　volumes；　Berlin；　1894…96。）　　It　has；　however；　been　frequently　challenged；　both　by　botanists　and　zoologists；　chiefly　owing　to　the　fact　that　many　have　failed　to　distinguish　its　two　essential　elements；　palingenesis　and　cenogenesis。　　As　early　as　1874　I　had　emphasised；　in　the　first　chapter　of　my　〃Evolution　of　Man〃；　the　importance　of　discriminating　carefully　between　these　two　sets　of　phenomena：

〃In　the　evolutionary　appreciation　of　the　facts　of　embryology　we　must　take　particular　care　to　distinguish　sharply　and　clearly　between　the　primary；　palingenetic　evolutionary　processes　and　the　secondary；　cenogenetic　processes。　　The　palingenetic　phenomena；　or　embryonic　RECAPITULATIONS；　are　due　to　heredity；　to　the　transmission　of　characters　from　one　generation　to　another。　　They　enable　us　to　draw　direct　inferences　in　regard　to　corresponding　structures　in　the　development　of　the　species　（e。g。　the　chorda　or　the　branchial　arches　in　all　vertebrate　embryos）。　　The　cenogenetic　phenomena；　on　the　other　hand；　or　the　embryonic　VARIATIONS；　cannot　be　traced　to　inheritance　from　a　mature　ancestor；　but　are　due　to　the　adaptation　of　the　embryo　or　the　larva　to　certain　conditions　of　its　individual　development　（e。g。　the　amnion；　the　allantois；　and　the　vitelline　arteries　in　the　embryos　of　the　higher　vertebrates）。　　These　cenogenetic　phenomena　are　later　additions；　we　must　not　infer　from　them　that　there　were　corresponding　processes　in　the　ancestral　history；　and　hence　they　are　apt　to　mislead。〃

The　fundamental　importance　of　these　facts　of　comparative　anatomy；　atavism；　and　the　rudimentary　organs；　was　pointed　out　by　Darwin　in　the　first　part　of　his　classic　work；　〃The　Descent　of　Man　and　Selection　in　Relation　to　Sex〃　（1871）。　　（〃Descent　of　Man〃　（Popular　Edition）；　page　927。）　　In　the　〃General　summary　and　conclusion〃　（chapter　XXI。）　he　was　able　to　say；　with　perfect　justice：　　〃He　who　is　not　content　to　look；　like　a　savage；　at　the　phenomena　of　nature　as　disconnected；　cannot　any　longer　believe　that　man　is　the　work　of　a　separate　act　of　creation。　　He　will　be　forced　to　admit　that　the　close　resemblance　of　the　embryo　of　man　to　that；　for　instance；　of　a　dogthe　construction　of　his　skull；　limbs；　and　whole　frame　on　the　same　plan　with　that　of　other　mammals；　independently　of　the　uses　to　which　the　parts　may　be　putthe　occasional　reappearance　of　various　structures；　for　instance　of　several　muscles；　which　man　does　not　normally　possess；　but　which　are　common　to　the　Quadrumanaand　a　crowd　of　analogous　factsall　point　in　the　plainest　manner　to　the　conclusion　that　man　is　the　co…descendant　with　other　mammals　of　a　common　progenitor。〃

These　few　lines　of　Darwin's　have　a　greater　scientific　value　than　hundreds　of　those　so…called　〃anthropological　treatises；〃　which　give　detailed　descriptions　of　single　organs；　or　mathematical　tables　with　series　of　numbers　and　what　are　claimed　to　be　〃exact　analyses；〃　but　are　devoid　of　synoptic　conclusions　and　a　philosophical　spirit。

Charles　Darwin　is　not　generally　recognised　as　a　great　anthropologist；　nor　does　the　school　of　modern　anthropologists　regard　him　as　a　leading　authority。　　In　Germany；　especially；　the　great　majority　of　the　members　of　the　anthropological　societies　took　up　an　attitude　of　hostility　to　him　from　the　very　beginning　of　the　controversy　in　1860。　　〃The　Descent　of　Man〃　was　not　merely　rejected；　but　even　the　discussion　of　it　was　forbidden　on　the　ground　that　it　was　〃unscientific。〃

The　centre　of　this　inveterate　hostility　for　thirty　yearsespecially　after　1877was　Rudolph　Virchow　of　Berlin；　the　leading　investigator　in　pathological　anatomy；　who　did　so　much　for　the　reform　of　medicine　by　his　establishment　of　cellular　pathology　in　1858。　　As　a　prominent　representative　of　〃exact〃　or　〃descriptive〃　anthropology；　and　lacking　a　broad　equipment　in　comparative　anatomy　and　ontogeny；　he　was　unable　to　accept　the　theory　of　descent。　　In　earlier　years；　and　especially　during　his　splendid　period　of　activity　at　Wurzburg　（1848…1856）；　he　h