the darwinian hypothesis-第4节

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for　the　struggle　in　which　they　are　engaged；　then　the　chances　are　in
favour；　not　only　of　these　individuals　being　better　nourished　than　the
others；　but　of　their　predominating　over　their　fellows　in　other　ways；　and
of　having　a　better　chance　of　leaving　offspring；　which　will　of　course
tend　to　reproduce　the　peculiarities　of　their　parents。　　Their　offspring
will；　by　a　parity　of　reasoning；　tend　to　predominate　over　their
contemporaries；　and　there　being　（suppose）　no　room　for　more　than　one
species　such　as　A；　the　weaker　variety　will　eventually　be　destroyed　by
the　new　destructive　influence　which　is　thrown　into　the　scale；　and　the
stronger　will　take　its　place。　　Surrounding　conditions　remaining
unchanged；　the　new　variety　（which　we　may　call　B）supposed；　for
argument's　sake；　to　be　the　best　adapted　for　these　conditions　which　can
be　got　out　of　the　original　stockwill　remain　unchanged；　all　accidental
deviations　from　the　type　becoming　at　once　extinguished；　as　less　fit　for
their　post　than　B　itself。　　The　tendency　of　B　to　persist　will　grow　with
its　persistence　through　successive　generations；　and　it　will　acquire　all
the　characters　of　a　new　species。

But；　on　the　other　hand；　if　the　conditions　of　life　change　in　any　degree；
however　slight；　B　may　no　longer　be　that　form　which　is　best　adapted　to
withstand　their　destructive；　and　profit　by　their　sustaining；　influence；
in　which　case　if　it　should　give　rise　to　a　more　competent　variety　（C）；
this　will　take　its　place　and　become　a　new　species；　and　thus；　by
'natural　selection'；　the　species　B　and　C　will　be　successively　derived
from　A。

That　this　most　ingenious　hypothesis　enables　us　to　give　a　reason　for　many
apparent　anomalies　in　the　distribution　of　living　beings　in　time　and
space；　and　that　it　is　not　contradicted　by　the　main　phenomena　of　life
and　organization　appear　to　us　to　be　unquestionable；　and　so　far　it　must
be　admitted　to　have　an　immense　advantage　over　any　of　its　predecessors。
But　it　is　quite　another　matter　to　affirm　absolutely　either　the　truth　or
falsehood　of　Mr。　Darwin's　views　at　the　present　stage　of　the　inquiry。
Goethe　has　an　excellent　aphorism　defining　that　state　of　mind　which　he
calls　'Thatige　Skepsis'aactive　doubt。　　It　is　doubt　which　so　loves
truth　that　it　neither　dares　rest　in　doubting；　nor　extinguish　itself　by
unjustified　belief；　and　we　commend　this　state　of　mind　to　students　of
species；　with　respect　to　Mr。　Darwin's　or　any　other　hypothesis；　as　to
their　origin。　The　combined　investigations　of　another　20　years　may；
perhaps；　enable　naturalists　to　say　whether　the　modifying　causes　and　the
selective　power；　which　Mr。　Darwin　has　satisfactorily　shown　to　exist　in
nature；　are　competent　to　produce　all　the　effects　he　ascribes　to　them；
or　whether；　on　the　other　hand；　he　has　been　led　to　over…estimate　the
value　of　his　principle　of　natural　selection；　as　greatly　as　Lamarck
overestimated　his　vera　causa　of　modification　by　exercise。

But　there　is；　at　all　events；　one　advantage　possessed　by　the　more　recent
writer　over　his　predecessor。　　Mr。　Darwin　abhors　mere　speculation　as
nature　abhors　a　vacuum。　　He　is　as　greedy　of　cases　and　precedents　as　any
constitutional　lawyer；　and　all　the　principles　he　lays　down　are　capable
of　being　brought　to　the　test　of　observation　and　experiment。　　The　path
he　bids　us　follow　professes　to　be；　not　a　mere　airy　track；　fabricated　of
ideal　cobwebs；　but　a　solid　and　broad　bridge　of　facts。　　If　it　be　so；　it
will　carry　us　safely　over　many　a　chasm　in　our　knowledge；　and　lead　us　to
a　region　free　from　the　snares　of　those　fascinating　but　barren　Virgins；
the　Final　Causes；　against　whom　a　high　authority　has　so　justly　warned　us。
〃My　sons；　dig　in　the　vineyard；〃　were　the　last　words　of　the　old　man　in
the　fable；　and；　though　the　sons　found　no　treasure；　they　made　their
fortunes　by　the　grapes。







End