a critical examination of on the origin of species-第4章

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far　as　experiments　have　gone；　it　has　not　been　found　possible　to　produce
this　complete　physiological　divergence　by　selective　breeding。　　I　stated
this　very　clearly　before；　and　I　now　refer　to　the　point；　because；　if　it
could　be　proved；　not　only　that　this　'has'　not　been　done；　but　that　it
'cannot'　be　done；　if　it　could　be　demonstrated　that　it　is　impossible　to
breed　selectively；　from　any　stock；　a　form　which　shall　not　breed　with
another；　produced　from　the　same　stock；　and　if　we　were　shown　that　this
must　be　the　necessary　and　inevitable　results　of　all　experiments；　I　hold
that　Mr。　Darwin's　hypothesis　would　be　utterly　shattered。

But　has　this　been　done？　or　what　is　really　the　state　of　the　case？　　It　is
simply　that；　so　far　as　we　have　gone　yet　with　our　breeding；　we　have　not
produced　from　a　common　stock　two　breeds　which　are　not　more　or　less
fertile　with　one　another。

I　do　not　know　that　there　is　a　single　fact　which　would　justify　any　one　in
saying　that　any　degree　of　sterility　has　been　observed　between　breeds
absolutely　known　to　have　been　produced　by　selective　breeding　from　a
common　stock。　　On　the　other　hand；　I　do　not　know　that　there　is　a　single
fact　which　can　justify　any　one　in　asserting　that　such　sterility　cannot
be　produced　by　proper　experimentation。　　For　my　own　part；　I　see　every
reason　to　believe　that　it　may；　and　will　be　so　produced。　　For；　as　Mr。
Darwin　has　very　properly　urged；　when　we　consider　the　phenomena　of
sterility；　we　find　they　are　most　capricious；　we　do　not　know　what　it　is
that　the　sterility　depends　on。　　There　are　some　animals　which　will　not
breed　in　captivity；　whether　it　arises　from　the　simple　fact　of　their
being　shut　up　and　deprived　of　their　liberty；　or　not；　we　do　not　know；
but　they　certainly　will　not　breed。　　What　an　astounding　thing　this　is；　to
find　one　of　the　most　important　of　all　functions　annihilated　by　mere
imprisonment！

So；　again；　there　are　cases　known　of　animals　which　have　been　thought　by
naturalists　to　be　undoubted　species；　which　have　yielded　perfectly
fertile　hybrids；　while　there　are　other　species　which　present　what
everybody　believes　to　be　varieties*　which　are　more　or　less　infertile
with　one　another。　　There　are　other　cases　which　are　truly　extraordinary；
there　is　one；　for　example；　which　has　been　carefully　examined；of　two
kinds　of　sea…weed；　of　which　the　male　element　of　the　one；　which　we　may
call　A；　fertilizes　the　female　element　of　the　other；　B；　while　the　male
element　of　B　will　not　fertilize　the　female　element　of　A；　so　that；　while
the　former　experiment　seems　to　show　us　that　they　are　'varieties'；　the
latter　leads　to　the　conviction　that　they　are　'species'。

　　　　*＇footnote＇　And　as　I　conceive　with　very　good　reason；　but　if
　　　　any　objector　urges　that　we　cannot　prove　that　they　have　been
　　　　produced　by　artificial　or　natural　selection；　the　objection
　　　　must　be　admittedultrasceptical　as　it　is。　　But　in　science；
　　　　scepticism　is　a　duty。

When　we　see　how　capricious　and　uncertain　this　sterility　is；　how　unknown
the　conditions　on　which　it　depends；　I　say　that　we　have　no　right　to
affirm　that　those　conditions　will　not　be　better　understood　by　and　by；
and　we　have　no　ground　for　supposing　that　we　may　not　be　able　to
experiment　so　as　to　obtain　that　crucial　result　which　I　mentioned　just
now。　　So　that　though　Mr。　　Darwin's　hypothesis　does　not　completely
extricate　us　from　this　difficulty　at　present；　we　have　not　the　least
right　to　say　it　will　not　do　so。

There　is　a　wide　gulf　between　the　thing　you　cannot　explain　and　the　thing
that　upsets　you　altogether。　　There　is　hardly　any　hypothesis　in　this
world　which　has　not　some　fact　in　connection　with　it　which　has　not　been
explained；　but　that　is　a　very　different　affair　to　a　fact　that　entirely
opposes　your　hypothesis；　in　this　case　all　you　can　say　is；　that　your
hypothesis　is　in　the　same　position　as　a　good　many　others。

Now；　as　to　the　third　test；　that　there　are　no　other　causes　competent　to
explain　the　phenomena；　I　explained　to　you　that　one　should　be　able　to
say　of　an　hypothesis；　that　no　other　known　causes　than　those　supposed　by
it　are　competent　to　give　rise　to　the　phenomena。　　Here；　I　think；　Mr。
Darwin's　view　is　pretty　strong。　　I　really　believe　that　the　alternative
is　either　Darwinism　or　nothing；　for　I　do　not　know　of　any　rational
conception　or　theory　of　the　organic　universe　which　has　any　scientific
position　at　all　beside　Mr。　Darwin's。　　I　do　not　know　of　any　proposition
that　has　been　put　before　us　with　the　intention　of　explaining　the
phenomena　of　organic　nature；　which　has　in　its　favour　a　thousandth　part
of　the　evidence　which　may　be　adduced　in　favour　of　Mr。　Darwin's　views。
Whatever　may　be　the　objections　to　his　views；　certainly　all　others　are
absolutely　out　of　court。

Take　the　Lamarckian　hypothesis；　for　example。　　Lamarck　was　a　great
naturalist；　and　to　a　certain　extent　went　the　right　way　to　work；　he
argued　from　what　was　undoubtedly　a　true　cause　of　some　of　the　phenomena
of　organic　nature。　　He　said　it　is　a　matter　of　experience　that　an　animal
may　be　modified　more　or　less　in　consequence　of　its　desires　and
consequent　actions。　Thus；　if　a　man　exercise　himself　as　a　blacksmith；
his　arms　will　become　strong　and　muscular；　such　organic　modification　is
a　result　of　this　particular　action　and　exercise。　　Lamarck　thought　that
by　a　very　simple　supposition　based　on　this　truth　he　could　explain　the
origin　of　the　various　animal　species：　he　said；　for　example；　that　the
short…legged　birds　which　live　on　fish　had　been　converted　into　the
long…legged　waders　by　desiring　to　get　the　fish　without　wetting　their
bodies；　and　so　stretching　their　legs　more　and　more　through　successive
generations。　　If　Lamarck　could　have　shown　experimentally；　that　even
races　of　animals　could　be　produced　in　this　way；　there　might　have　been
some　ground　for　his　speculations。　　But　he　could　show　nothing　of　the
kind；　and　his　hypothesis　has　pretty　well　dropped　into　oblivion；　as　it
deserved　to　do。　　I　said　in　an　earlier　lecture　that　there　are　hypotheses
and　hypotheses；　and　when　people　tell　you　that　Mr。　　Darwin's
strongly…based　hypothesis　is　nothing　but　a　mere　modification　of
Lamarck's；　you　will　know　what　to　think　of　their　capacity　for　forming　a
judgment　on　this　subject。

But　you　must　recollect　that　when　I　say　I　think　it　is　either　Mr。　Darwin's
hypothesis　or　nothing；　that　either　we　must　take　his　view；　or　look　upon
the　whole　of　organic　nature　as　an　enigma；　the　meaning　of　which　is
wholly　hidden　from　us；　you　must　understand　that　I　mean　that　I　accept　it
provisionally；　in　exactly　the　same　way　as　I　accept　any　other　hypothesis。
Men　of　science　do　not　pledge　themselves　to　creeds；　they　are　bound　by
articles　of　no　sort；　there　is　not　a　single　belief　that　it　is　not　a
bounden　duty　with　them　to　hold　with　a　light　hand　and　to　part　with　it
cheerfully；　the　moment　it　is　really　proved　to　be　contrary　to　any　fact；
great　or　small。　　And　if；　in　course　of　time　I　see　good　reasons　for　such
a　proceeding；　I　shall　have　no　hesitation　in　coming　before　you；　and
pointing　out　any　change　in　my　opinion　without　finding　the　slightest
occasion　to　blush　for　so　doing。　　So　I　say　that　we　accept　this　view　as
we　accept　any　other；　so　long　as　it　will　help　us；　and　we　feel　bound　to
retain　it　only　so　long　as　it　will　serve　our　great　purposethe
improvement　of　Man's　estate　and　the　widening　of　his　knowledge。　　The
moment　this；　or　any　other　conception；　ceases　to　be　useful　for　these
purposes；　away　with　it　to　the　four　winds；　we　care　not　what　becomes　of
it！

But　to　say　truth；　although　it　has　been　my　business　to　attend　closely　to
the　controversies　roused　by　the　publication　of　Mr。　Darwin's　book；　I
think　that　not　one　of　the　enormous　mass　of　objections　and　obstacles
which　have　been　raised　is　of　any　very　great　value；　except　that
sterility　case　which　I　brought　before　you　just　now。　　All　the　rest　are
misunderstandings　of　some　sort；　arising　either　from　prejudice；　or　want
of　knowledge；　or　still　more　from　want　of　patience　and　care　in　reading
the　work。

For　you　must　recollect　that　it　is　not　a　book　to　be　read　with　as　much
ease　as　its　pleasant　style　may　lead　you　to　imagine。　　You　spin　through
it　as　if　it　were　a　novel　the　first　time　you　read　it；　and　think　you　know
all　about　it；　the　second　time　you　read　it　you　think　you　know　rather
less　about　i