darwin and modern science-第110章

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The　whole　subject　as　Darwin　realised　is　very　complex。　　Even　the　term　〃expression〃　has　a　certain　amount　of　ambiguity。　　When　the　emotion　is　in　full　flood　the　animal　fights；　flees；　or　faints。　　Is　this　full…tide　effect　to　be　regarded　as　expression；　or　are　we　to　restrict　the　term　to　the　premonitory　or　residual　effectsthe　bared　canine　when　the　fighting　mood　is　being　roused；　the　ruffled　fur　when　reminiscent　representations　of　the　object　inducing　anger　cross　the　mind？　　Broadly　considered　both　should　be　included。　　The　activity　of　premonitory　expression　as　a　means　of　communication　was　recognised　by　Darwin；　he　might；　perhaps；　have　emphasised　it　more　strongly　in　dealing　with　the　lower　animals。　　Man　so　largely　relies　on　a　special　means　of　communication；　that　of　language；　that　he　sometimes　fails　to　realise　that　for　animals　with　their　keen　powers　of　perception；　and　dependent　as　they　are　on　such　means　of　communication；　the　more　strictly　biological　means　of　expression　are　full　of　subtle　suggestiveness。　　Many　modes　of　expression；　otherwise　useless；　are　signs　of　behaviour　that　may　be　anticipated；signs　which　stimulate　the　appropriate　attitude　of　response。　　This　would　not；　however；　serve　to　account　for　the　utility　of　the　organic　accompanimentsheart…affection；　respiratory　changes；　vaso…motor　effects　and　so　forth；　together　with　heightened　muscular　tone；on　all　of　which　Darwin　lays　stress　（〃Expression　of　the　Emotions〃；　pages　65　ff。）　under　his　third　principle。　　The　biological　value　of　all　this　is；　however；　of　great　importance；　though　Darwin　was　hardly　in　a　position　to　take　it　fully　into　account。

Having　regard　to　the　instinctive　and　hereditary　factors　of　emotional　expression　we　may　ask　whether　Darwin's　third　principle　does　not　alone　suffice　as　an　explanation。　　Whether　we　admit　or　reject　Lamarckian　inheritance　it　would　appear　that　all　hereditary　expression　must　be　due　to　pre…established　connections　within　the　central　nervous　system　and　to　a　transmitted　provision　for　coordinated　response　under　the　appropriate　stimulation。　　If　this　be　so；　Darwin's　first　and　second　principles　are　subordinate　and　ancillary　to　the　third；　an　expression；　so　far　as　it　is　instinctive　or　hereditary；　being　〃the　direct　result　of　the　constitution　of　the　nervous　system。〃

Darwin　accepted　the　emotions　themselves　as　hereditary　or　acquired　states　of　mind　and　devoted　his　attention　to　their　expression。　　But　these　emotions　themselves　are　genetic　products　and　as　such　dependent　on　organic　conditions。　　It　remained；　therefore；　for　psychologists　who　accepted　evolution　and　sought　to　build　on　biological　foundations　to　trace　the　genesis　of　these　modes　of　animal　and　human　experience。　　The　subject　has　been　independently　developed　by　Professors　Lange　and　James　（Cf。　William　James；　〃Principles　of　Psychology〃；　Vol。　II。　Chap。　XXV；　London；　1890。）；　and　some　modification　of　their　view　is　regarded　by　many　evolutionists　as　affording　the　best　explanation　of　the　facts。　　We　must　fix　our　attention　on　the　lower　emotions；　such　as　anger　or　fear；　and　on　their　first　occurrence　in　the　life　of　the　individual　organism。　　It　is　a　matter　of　observation　that　if　a　group　of　young　birds　which　have　been　hatched　in　an　incubator　are　frightened　by　an　appropriate　presentation；　auditory　or　visual；　they　instinctively　respond　in　special　ways。　　If　we　speak　of　this　response　as　the　expression；　we　find　that　there　are　many　factors。　　There　are　certain　visible　modes　of　behaviour；　crouching　at　once；　scattering　and　then　crouching；　remaining　motionless；　the　braced　muscles　sustaining　an　attitude　of　arrest；　and　so　forth。　　There　are　also　certain　visceral　or　organic　effects；　such　as　affections　of　the　heart　and　respiration。　　These　can　be　readily　observed　by　taking　the　young　bird　in　the　hand。　　Other　effects　cannot　be　readily　observed；　vaso…motor　changes；　affections　of　the　alimentary　canal；　the　skin　and　so　forth。　　Now　the　essence　of　the　James…Lange　view；　as　applied　to　these　congenital　effects；　is　that　though　we　are　justified　in　speaking　of　them　as　effects　of　the　stimulation；　we　are　not　justified；　without　further　evidence；　in　speaking　of　them　as　effects　of　the　emotional　state。　　May　it　not　rather　be　that　the　emotion　as　a　primary　mode　of　experience　is　the　concomitant　of　the　net　result　of　the　organic　situationthe　initial　presentation；　the　instinctive　mode　of　behaviour；　the　visceral　disturbances？　　According　to　this　interpretation　the　primary　tissue　of　experience　of　the　emotional　order；　felt　as　an　unanalysed　complex；　is　generated　by　the　stimulation　of　the　sensorium　by　afferent　or　incoming　physiological　impulses　from　the　special　senses；　from　the　organs　concerned　in　the　responsive　behaviour；　from　the　viscera　and　vaso…motor　system。

Some　psychologists；　however；　contend　that　the　emotional　experience　is　generated　in　the　sensorium　prior　to；　and　not　subsequent　to；　the　behaviour…　response　and　the　visceral　disturbances。　　It　is　a　direct　and　not　an　indirect　outcome　of　the　presentation　to　the　special　senses。　　Be　this　as　it　may；　there　is　a　growing　tendency　to　bring　into　the　closest　possible　relation；　or　even　to　identify；　instinct　and　emotion　in　their　primary　genesis。　　The　central　core　of　all　such　interpretations　is　that　instinctive　behaviour　and　experience；　its　emotional　accompaniments；　and　its　expression；　are　but　different　aspects　of　the　outcome　of　the　same　organic　occurrences。　　Such　emotions　are；　therefore；　only　a　distinguishable　aspect　of　the　primary　tissue　of　experience　and　exhibit　a　like　differentiation。　　Here　again　a　biological　foundation　is　laid　for　a　psychological　doctrine　of　the　mental　development　of　the　individual。

The　intimate　relation　between　emotion　as　a　psychological　mode　of　experience　and　expression　as　a　group　of　organic　conditions　has　an　important　bearing　on　biological　interpretation。　　The　emotion；　as　the　psychological　accompaniment　of　orderly　disturbances　in　the　central　nervous　system　profoundly　influences　behaviour　and　often　renders　it　more　vigorous　and　more　effective。　　The　utility　of　the　emotions　in　the　struggle　for　existence　can；　therefore；　scarcely　be　over…estimated。　　Just　as　keenness　of　perception　has　survival…　value；　just　as　it　is　obviously　subject　to　variation；　just　as　it　must　be　enhanced　under　natural　selection；　whether　individually　acquired　increments　are　inherited　or　not；　and　just　as　its　value　lies　not　only　in　this　or　that　special　perceptive　act　but　in　its　importance　for　life　as　a　whole；　so　the　vigorous　effectiveness　of　activity　has　survival…value；　it　is　subject　to　variation；　it　must　be　enhanced　under　natural　selection；　and　its　importance　lies　not　only　in　particular　modes　of　behaviour　but　in　its　value　for　life　as　a　whole。　　If　emotion　and　its　expression　as　a　congenital　endowment　are　but　different　aspects　of　the　same　biological　occurrence；　and　if　this　is　a　powerful　supplement　to　vigour　effectiveness　and　persistency　of　behaviour；　it　must　on　Darwin's　principles　be　subject　to　natural　selection。

If　we　include　under　the　expression　of　the　emotions　not　only　the　premonitory　symptoms　of　the　initial　phases　of　the　organic　and　mental　state；　not　only　the　signs　or　conditions　of　half…tide　emotion；　but　the　full…tide　manifestation　of　an　emotion　which　dominates　the　situation；　we　are　naturally　led　on　to　the　consideration　of　many　of　the　phenomena　which　are　discussed　under　the　head　of　sexual　selection。　　The　subject　is　difficult　and　complex；　and　it　was　treated　by　Darwin　with　all　the　strength　he　could　summon　to　the　task。　　It　can　only　be　dealt　with　here　from　a　special　point　of　viewthat　which　may　serve　to　illustrate　the　influence　of　certain　mental　factors　on　the　course　of　evolution。　　From　this　point　of　view　too　much　stress　can　scarcely　be　laid　on　the　dominance　of　emotion　during　the　period　of　courtship　and　pairing　in　the　more　highly　organised　animals。　　It　is　a　period　of　maximum　vigour；　maximum　activity；　and；　correlated　with　special　modes　of　behaviour　and　special　organic　and　visceral　accompaniments；　a　period　also　of　maximum　emotional　excitement。　　The　combats　of　males；　their　dances　and　aerial　evolutions；　their　elaborate　behaviour　and　display；　or　the　flood　of　song　in　birds；　are　emotional　expressions　which　are　at　any　rate　coincident　in　time　with　sexual　periodicity。　　From　the　combat　of　the　males　there　follows　on　Darwin's　principles　the　elimination　of　those　which　are　deficient　in　bodily　vigour；　deficient　in　special　structures；　offensive　or　protective；　which　contribute　to　success；　deficient　in　the　emotional　supplement　of　which　persistent　and　whole…hearted　fighting　is　the　expression；　and　deficient　in　alertness　and　skill　which　are　the　outcome　of　the　psychological　development　of　the　powers　of　perception。　　Few　biologists　question　that　we　have　here　a　mode　of　selection　of　much　importance；　though　its　influence　on　psychological　evolution　often　fails　to　receive　its　due　emphasis。　　Mr　Wallace　（〃Darwinism〃；　pages　282；　283；　London；　1889。）　regards　it　as　〃a　form　of　natural　selection〃；　〃to　it；〃　he　says；　〃we　must　impute　the　development　of　the　exceptional　strength；　size；　and　activity　of　the　male；　together　with　the　possession　of　special　offensive　and　defensive　weapons；　and　of　all　other　characters　which　arise　from　the　development　of　these　or　are　correlated　with　them。〃　　So　far　there　is　little　disagreement　among　the　followers　of　Darwin　for　Mr　Wallace；　with　fine　magnanimity；　has　always　preferred　to　be　ranked　as　such；　notwithstanding　his　right；　on　which　a　smaller　man　would　have　constantly　insisted；　to　the　claim　of　independent　originator　of　the　doctrine　of　natural　selection。　　So　far　with　regard　to　sexual　selection　Darwin　and　Mr　Wallace　are　agreed；　so　far　and　no　farther。　　For　Darwin；　says　Mr　Wallace　（Ibid。　page　283。）；　〃has　extended　the　principle　into　a　totally　different　field　of　action；　which　has　none　of　that　character　of　constancy　and　of　inevitable　result　that　attaches　to　natural　selection；　including　male　rivalry；　for　by　far　the　larger　portion　of　the　phenomena；　which　he　endeavours　to　explain　by　the　direct　action　of　sexual　selection；　can　only　be　so　explained　on　the　hypothesis　that　the　immediate　agency　is　female　choice　or　preference。　　It　is　to　this　that　he　imputes　the　origin　of　all　secondary　sexual　characters　other　than　weapons　of　offence　and　defence。。。In　this　extension　of　sexual　selection　to　include　the　action　of　female　choice　or　preference；　and　in　the　attempt　to　give　to　that　choice　such　wide…reaching　effects；　I　am　unable　to　follow　him　more　than　a　very　little　way。〃

Into　the　details　of　Mr　Wallace's　criticisms　it　is　impossible　to　enter　here。　We　cannot　discuss　either　the　mode　of　origin　of　the　variations　in　structure　which　have　rendered　secondary　sexual　characters　possible　or　the　modes　of　selection　other　than　sexual　which　have　rendered　them；　within　narrow　limits；　specifically　constant。　　Mendelism　and　mutation　theories　may　have　something　to　say　on　the　subject　when　these　theories　have　been　more　fully　correlated　with　the　basal　principles　of　selection。　　It　is　noteworthy　that　Mr　Wallace　says　（〃Darwinism〃；　pages　283；　284。）：　　〃Besides　the　acquisition　of　weapons　by　the　male　for　the　purpose　of　fighting　with　other　males；　there　are　some　other　sexual　characters　which　may　have　been　produced　by　natural　selection。　Such　are　the　various　sounds　and　odours　which　are　peculiar　to　the　male；　and　which　serve　as　a　call　to　the　female　or　as　an　indication　of　his　presence。　　These　are　evidently　a　valuable　addition　to　the　means　of　recognitio