darwin and modern science-第96章

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ey's　very　interesting　work　on　Natural　Theology；　and　the　very　popular　lectures　of　Dr　Kidd　on　Comparative　Anatomy；　and　Dr　Buckland　on　Geology。〃　　In　the　arrangement　of　the　contents　of　the　Museum　the　illustration　of　Paley's　work　was　given　the　foremost　place　by　J。S。　Duncan：　　〃The　first　division　proposes　to　familiarize　the　eye　to　those　relations　of　all　natural　objects　which　form　the　basis　of　argument　in　Dr　Paley's　Natural　Theology；　to　induce　a　mental　habit　of　associating　the　view　of　natural　phenomena　with　the　conviction　that　they　are　the　media　of　Divine　manifestation；　and　by　such　association　to　give　proper　dignity　to　every　branch　of　natural　science。〃　　（（From　〃History　and　Arrangement　of　the　Ashmolean　Museum〃　by　P。B。　Duncan：　　see　pages　vi；　vii　of　〃A　Catalogue　of　the　Ashmolean　Museum〃；　Oxford；　1836。）

The　great　naturalist；　W。J。　Burchell；　in　his　classical　work　shows　the　same　recognition　of　adaptation　in　nature　at　a　still　earlier　date。　　Upon　the　subject　of　collections　he　wrote　（〃Travels　in　the　Interior　of　Southern　Africa〃；　London；　Vol。　I。　1822；　page　505。　　The　references　to　Burchell's　observations　in　the　present　essay　are　adapted　from　the　author's　article　in　〃Report　of　the　British　and　South　African　Associations〃；　1905；　Vol。　III。　pages　57…110。）：　　〃It　must　not　be　supposed　that　these　charms　（the　pleasures　of　Nature）　are　produced　by　the　mere　discovery　of　new　objects：　　it　is　the　harmony　with　which　they　have　been　adapted　by　the　Creator　to　each　other；　and　to　the　situations　in　which　they　are　found；　which　delights　the　observer　in　countries　where　Art　has　not　yet　introduced　her　discords。〃　　The　remainder　of　the　passage　is　so　admirable　that　I　venture　to　quote　it：　　〃To　him　who　is　satisfied　with　amassing　collections　of　curious　objects；　simply　for　the　pleasure　of　possessing　them；　such　objects　can　afford；　at　best；　but　a　childish　gratification；　faint　and　fleeting；　while　he　who　extends　his　view　beyond　the　narrow　field　of　nomenclature；　beholds　a　boundless　expanse；　the　exploring　of　which　is　worthy　of　the　philosopher；　and　of　the　best　talents　of　a　reasonable　being。〃

On　September　14；　1811；　Burchell　was　at　Zand　Valley　（Vlei）；　or　Sand　Pool；　a　few　miles　south…west　of　the　site　of　Prieska；　on　the　Orange　River。　　Here　he　found　a　Mesembryanthemum　（M。　turbiniforme；　now　M。　truncatum）　and　also　a　〃Gryllus〃　（Acridian）；　closely　resembling　the　pebbles　with　which　their　locality　was　strewn。　　He　says　of　both　of　these；　〃The　intention　of　Nature；　in　these　instances；　seems　to　have　been　the　same　as　when　she　gave　to　the　Chameleon　the　power　of　accommodating　its　color；　in　a　certain　degree；　to　that　of　the　object　nearest　to　it；　in　order　to　compensate　for　the　deficiency　of　its　locomotive　powers。　　By　their　form　and　colour；　this　insect　may　pass　unobserved　by　those　birds；　which　otherwise　would　soon　extirpate　a　species　so　little　able　to　elude　its　pursuers；　and　this　juicy　little　Mesembryanthemum　may　generally　escape　the　notice　of　cattle　and　wild　animals。〃　　（Loc。　cit。　pages　310；　311。　　See　Sir　William　Thiselton…Dyer　〃Morphological　Notes〃；　XI。；　〃Protective　Adaptations〃；　I。；　〃Annals　of　Botany〃；　Vol。　XX。　page　124。　　In　plates　VII。；　VIII。　and　IX。　accompanying　this　article　the　author　represents　the　species　observed　by　Burchell；　together　with　others　in　which　analogous　adaptations　exist。　　He　writes：　　〃Burchell　was　clearly　on　the　track　on　which　Darwin　reached　the　goal。　　But　the　time　had　not　come　for　emancipation　from　the　old　teleology。　　This；　however；　in　no　respect　detracts　from　the　merit　or　value　of　his　work。　　For；　as　Huxley　has　pointed　out　（〃Life　and　Letters　of　Thomas　Henry　Huxley〃；　London；　1900；　I。　page　457）；　the　facts　of　the　old　teleology　are　immediately　transferable　to　Darwinism；　which　simply　supplies　them　with　a　natural　in　place　of　a　supernatural　explanation。〃）　　Burchell　here　seems　to　miss；　at　least　in　part；　the　meaning　of　the　relationship　between　the　quiescence　of　the　Acridian　and　its　cryptic　colouring。　　Quiescence　is　an　essential　element　in　the　protective　resemblance　to　a　stoneprobably　even　more　indispensable　than　the　details　of　the　form　and　colouring。　　Although　Burchell　appears　to　overlook　this　point　he　fully　recognised　the　community　between　protection　by　concealment　and　more　aggressive　modes　of　defence；　for；　in　the　passage　of　which　a　part　is　quoted　above；　he　specially　refers　to　some　earlier　remarks　on　page　226　of　his　Vol。　I。　　We　here　find　that　even　when　the　oxen　were　resting　by　the　Juk　rivier　（Yoke　river）；　on　July　19；　1811；　Burchell　observed　〃Geranium　spinosum；　with　a　fleshy　stem　and　large　white　flowers。。。；　and　a　succulent　species　of　Pelargonium。。。so　defended　by　the　old　panicles；　grown　to　hard　woody　thorns；　that　no　cattle　could　browze　upon　it。〃　　He　goes　on　to　say；　〃In　this　arid　country；　where　every　juicy　vegetable　would　soon　be　eaten　up　by　the　wild　animals；　the　Great　Creating　Power；　with　all…provident　wisdom；　has　given　to　such　plants　either　an　acrid　or　poisonous　juice；　or　sharp　thorns；　to　preserve　the　species　from　annihilation。。。〃　　All　these　modes　of　defence；　especially　adapted　to　a　desert　environment；　have　since　been　generally　recognised；　and　it　is　very　interesting　to　place　beside　Burchell's　statement　the　following　passage　from　a　letter　written　by　Darwin；　Aug。　7；　1868；　to　G。H。　Lewes；　　〃That　Natural　Selection　would　tend　to　produce　the　most　formidable　thorns　will　be　admitted　by　every　one　who　has　observed　the　distribution　in　South　America　and　Africa　（vide　Livingstone）　of　thorn…　bearing　plants；　for　they　always　appear　where　the　bushes　grow　isolated　and　are　exposed　to　the　attacks　of　mammals。　　Even　in　England　it　has　been　noticed　that　all　spine…bearing　and　sting…bearing　plants　are　palatable　to　quadrupeds；　when　the　thorns　are　crushed。〃　　（〃More　Letters〃；　I。　page　308。）

ADAPTATION　AND　NATURAL　SELECTION。

I　have　preferred　to　show　the　influence　of　the　older　teleology　upon　Natural　History　by　quotations　from　a　single　great　and　insufficiently　appreciated　naturalist。　　It　might　have　been　seen　equally　well　in　the　pages　of　Kirby　and　Spence　and　those　of　many　other　writers。　　If　the　older　naturalists　who　thought　and　spoke　with　Burchell　of　〃the　intention　of　Nature〃　and　the　adaptation　of　beings　〃to　each　other；　and　to　the　situations　in　which　they　are　found；〃　could　have　conceived　the　possibility　of　evolution；　they　must　have　been　led；　as　Darwin　was；　by　the　same　considerations　to　Natural　Selection。　　This　was　impossible　for　them；　because　the　philosophy　which　they　followed　contemplated　the　phenomena　of　adaptation　as　part　of　a　static　immutable　system。　　Darwin；　convinced　that　the　system　is　dynamic　and　mutable；　was　prevented　by　these　very　phenomena　from　accepting　anything　short　of　the　crowning　interpretation　offered　by　Natural　Selection。　　（〃I　had　always　been　much　struck　by　such　adaptations　（e。g。　woodpecker　and　tree…frog　for　climbing；　seeds　for　dispersal）；　and　until　these　could　be　explained　it　seemed　to　me　almost　useless　to　endeavour　to　prove　by　indirect　evidence　that　species　have　been　modified。〃　　〃Autobiography〃　in　〃Life　and　Letters　of　Charles　Darwin〃；　Vol。　I。　page　82。　　The　same　thought　is　repeated　again　and　again　in　Darwin's　letters　to　his　friends。　　It　is　forcibly　urged　in　the　Introduction　to　the　〃Origin〃　（1859）；　page　3。）　　And　the　birth　of　Darwin's　unalterable　conviction　that　adaptation　is　of　dominant　importance　in　the　organic　world；a　conviction　confirmed　and　ever　again　confirmed　by　his　experience　as　a　naturalistmay　probably　be　traced　to　the　influence　of　the　great　theologian。　　Thus　Darwin；　speaking　of　his　Undergraduate　days；　tells　us　in　his　〃Autobiography〃　that　the　logic　of　Paley's　〃Evidences　of　Christianity〃　and　〃Moral　Philosophy〃　gave　him　as　much　delight　as　did　Euclid。

〃The　careful　study　of　these　works；　without　attempting　to　learn　any　part　by　rote；　was　the　only　part　of　the　academical　course　which；　as　I　then　felt　and　as　I　still　believe；　was　of　the　least　use　to　me　in　the　education　of　my　mind。　I　did　not　at　that　time　trouble　myself　about　Paley's　premises；　and　taking　these　on　trust；　I　was　charmed　and　convinced　by　the　long　line　of　argumentation。〃　　（〃Life　and　Letters〃；　I。　page　47。）

When　Darwin　came　to　write　the　〃Origin〃　he　quoted　in　relation　to　Natural　Selection　one　of　Paley's　conclusions。　　〃No　organ　will　be　formed；　as　Paley　has　remarked；　for　the　purpose　of　causing　pain　or　for　doing　an　injury　to　its　possessor。〃　　（〃Origin　of　S