the darwinian hypothesis-第2章

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however　various　the　course　which　each　has　to　pursue。　　Not　only　men　and
horses；　and　cats　and　dogs；　lobsters　and　beetles；　periwinkles　and
mussels；　but　even　the　very　sponges　and　animalcules　commence　their
existence　under　forms　which　are　essentially　undistinguishable；　and　this
is　true　of　all　the　infinite　variety　of　plants。　　Nay；　more；　all　living
beings　march　side　by　side　along　the　high　road　of　development；　and
separate　the　later　the　more　like　they　are；　like　people　leaving　church；
who　all　go　down　the　aisle；　but　having　reached　the　door　some　turn　into
the　parsonage；　others　go　down　the　village；　and　others　part　only　in　the
next　parish。　　A　man　in　his　development　runs　for　a　little　while　parallel
with；　though　never　passing　through；　the　form　of　the　meanest　worm；　then
travels　for　a　space　beside　the　fish；　then　journeys　along　with　the　bird
and　the　reptile　for　his　fellow　travellers；　and　only　at　last；　after　a
brief　companionship　with　the　highest　of　the　four…footed　and　four…handed
world；　rises　into　the　dignity　of　pure　manhood。　　No　competent　thinker　of
the　present　day　dreams　of　explaining　these　indubitable　facts　by　the
notion　of　the　existence　of　unknown　and　undiscoverable　adaptations　to
purpose。　　And　we　would　remind　those　who；　ignorant　of　the　facts；　must　be
moved　by　authority；　that　no　one　has　asserted　the　incompetence　of　the
doctrine　of　final　causes；　in　its　application　to　physiology　and　anatomy；
more　strongly　than　our　own　eminent　anatomist；　Professor　Owen；　who；
speaking　of　such　cases；　says　（'On　the　Nature　of　Limbs'；　pp。　39；　40）：　〃I
think　it　will　be　obvious　that　the　principle　of　final　adaptations　fails
to　satisfy　all　the　conditions　of　the　problem。〃

But；　if　the　doctrine　of　final　causes　will　not　help　us　to　comprehend　the
anomalies　of　living　structure；　the　principle　of　adaptation　must　surely
lead　us　to　understand　why　certain　living　beings　are　found　in　certain
regions　of　the　world　and　not　in　others。　　The　palm；　as　we　know；　will　not
grow　in　our　climate；　nor　the　oak　in　Greenland。　　The　white　bear　cannot
live　where　the　tiger　thrives；　nor　'vice　versa'；　and　the　more　the
natural　habits　of　animal　and　vegetable　species　are　examined；　the　more
do　they　seem；　on　the　whole；　limited　to　particular　provinces。　　But　when
we　look　into　the　facts　established　by　the　study　of　the　geographical
distribution　of　animals　and　plants　it　seems　utterly　hopeless　to　attempt
to　understand　the　strange　and　apparently　capricious　relations　which
they　exhibit。　　One　would　be　inclined　to　suppose　'a　priori'　that　every
country　must　be　naturally　peopled　by　those　animals　that　are　fittest　to
live　and　thrive　in　it。　　And　yet　how；　on　this　hypothesis；　are　we　to
account　for　the　absence　of　cattle　in　the　Pampas　of　South　America；　when
those　parts　of　the　New　World　were　discovered？　　It　is　not　that　they　were
unfit　for　cattle；　for　millions　of　cattle　now　run　wild　there；　and　the
like　holds　good　of　Australia　and　New　Zealand。　　It　is　a　curious
circumstance；　in　fact；　that　the　animals　and　plants　of　the　Northern
Hemisphere　are　not　only　as　well　adapted　to　live　in　the　Southern
Hemisphere　as　its　own　autochthones；　but　are　in　many　cases　absolutely
better　adapted；　and　so　overrun　and　extirpate　the　aborigines。　　Clearly；
therefore；　the　species　which　naturally　inhabit　a　country　are　not
necessarily　the　best　adapted　to　its　climate　and　other　conditions。　　The
inhabitants　of　islands　are　often　distinct　from　any　other　known　species
of　animal　or　plants　（witness　our　recent　examples　from　the　work　of　Sir
Emerson　Tennent；　on　Ceylon）；　and　yet　they　have　almost　always　a　sort　of
general　family　resemblance　to　the　animals　and　plants　of　the　nearest
mainland。　　On　the　other　hand；　there　is　hardly　a　species　of　fish；　shell；
or　crab　common　to　the　opposite　sides　of　the　narrow　isthmus　of　Panama。
Wherever　we　look；　then；　living　nature　offers　us　riddles　of　difficult
solution；　if　we　suppose　that　what　we　see　is　all　that　can　be　known　of　it。

But　our　knowledge　of　life　is　not　confined　to　the　existing　world。
Whatever　their　minor　differences；　geologists　are　agreed　as　to　the　vast
thickness　of　the　accumulated　strata　which　compose　the　visible　part　of
our　earth；　and　the　inconceivable　immensity　of　the　time　of　whose　lapse
they　are　the　imperfect；　but　the　only　accessible　witnesses。　　Now；
throughout　the　greater　part　of　this　long　series　of　stratified　rocks　are
scattered；　sometimes　very　abundantly；　multitudes　of　organic　remains；
the　fossilized　exuviae　of　animals　and　plants　which　lived　and　died　while
the　mud　of　which　the　rocks　are　formed　was　yet　soft　ooze；　and　could
receive　and　bury　them。　　It　would　be　a　great　error　to　suppose　that　these
organic　remains　were　fragmentary　relics。　　Our　museums　exhibit　fossil
shells　of　immeasurable　antiquity；　as　perfect　as　the　day　they　were
formed；　whole　skeletons　without　a　limb　disturbednay；　the　changed
flesh；　the　developing　embryos；　and　even　the　very　footsteps　of　primieval
organisms。　　Thus　the　naturalist　finds　in　the　bowels　of　the　earth
species　as　well　defined　as；　and　in　some　groups　of　animals　more　numerous
than；　those　that　breathe　the　upper　air。　　But；　singularly　enough；　the
majority　of　these　entombed　species　are　wholly　distinct　from　those　that
now　live。　　Nor　is　this　unlikeness　without　its　rule　and　order。　　As　a
broad　fact；　the　further　we　go　back　in　time　the　less　the　buried　species
are　like　existing　forms；　and　the　further　apart　the　sets　of　extinct
creatures　are　the　less　they　are　like　one　another。　　In　other　words；
there　has　been　a　regular　succession　of　living　beings；　each　younger　set
being　in　a　very　broad　and　general　sense　somewhat　more　like　those　which
now　live。

It　was　once　supposed　that　this　succession　had　been　the　result　of　vast
successive　catastrophes；　destructions；　and　re…creations　'en　masse'；　but
catastrophes　are　now　almost　eliminated　from　geological；　or　at　least
palaeontological　speculation；　and　it　is　admitted　on　all　hands　that　the
seeming　breaks　in　the　chain　of　being　are　not　absolute；　but　only　relative
to　our　imperfect　knowledge；　that　species　have　replaced　species；　not　in
assemblages；　but　one　by　one；　and　that；　if　it　were　possible　to　have　all
the　phenomena　of　the　past　presented　to　us；　the　convenient　epochs　and
formations　of　the　geologist；　though　having　a　certain　distinctness；　would
fade　into　one　another　with　limits　as　undefinable　as　those　of　the
distinct　and　yet　separable　colours　of　the　solar　spectrum。

Such　is　a　brief　summary　of　the　main　truths　which　have　been　established
concerning　species。　Are　these　truths　ultimate　and　irresolvable　facts；
or　are　their　complexities　and　perplexities　the　mere　expressions　of　a
higher　law？

A　large　number　of　persons　practically　assume　the　former　position　to　be
correct。　　They　believe　that　the　writer　of　the　Pentateuch　was　empowered
and　commissioned　to　teach　us　scientific　as　well　as　other　truth；　that
the　account　we　find　there　of　the　creation　of　living　things　is　simply
and　literally　correct；　and　that　anything　which　seems　to　contradict　it
is；　by　the　nature　of　the　case；　false。　　All　the　phenomena　which　have
been　detailed　are；　on　this　view；　the　immediate　product　of　a　creative
fiat　and　consequently　are　out　of　the　domain　of　science　altogether。

Whether　this　view　prove　ultimately　to　be　true　or　false；　it　is；　at　any
rate；　not　at　present　supported　by　what　is　commonly　regarded　as　logical
proof；　even　if　it　be　capable　of　discussion　by　reason；　and　hence　we
consider　ourselves　at　liberty　to　pass　it　by；　and　to　turn　to　those　views
which　profess　to　rest　on　a　scientific　basis　only；　and　therefore　admit　of
being　argued　to　their　consequences。　　And　we　do　this　with　the　less
hesitation　as　it　so　happens　that　those　persons　who　are　practically
conversant　with　the　facts　of　the　case　（plainly　a　considerable　advantage）
have　always　thought　fit　to　range　themselves　under　the　latter　category。

The　majority　of　these　competent　persons　have　up　to　the　present　time
maintained　two　positions；the　first；　that　every　species　is；　within
certain　defined　or　definable　limits；　fixed　and　incapable　of
modification；　the　second；　that　every　species　was　originally　produced　by
a　distinct　creative　act。　　The　second　position　is　obviously　incapable　of
proof　or　disproof；　the　direct　operations　of　the　Creator　not　being
subjects　of　science；　and　it　must　therefore