the origination of living beings-第3章

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and　is　sure　to　be　constantly　productive　of　mischievous；　if　not　fatal
results。

Do　not　allow　yourselves　to　be　misled　by　the　common　notion　that　an
hypothesis　is　untrustworthy　simply　because　it　is　an　hypothesis。　　It　is
often　urged；　in　respect　to　some　scientific　conclusion；　that；　after　all；
it　is　only　an　hypothesis。　　But　what　more　have　we　to　guide　us　in
nine…tenths　of　the　most　important　affairs　of　daily　life　than　hypotheses；
and　often　very　ill…based　ones？　　So　that　in　science；　where　the　evidence
of　an　hypothesis　is　subjected　to　the　most　rigid　examination；　we　may
rightly　pursue　the　same　course。　　You　may　have　hypotheses　and
hypotheses。　　A　man　may　say；　if　he　likes；　that　the　moon　is　made　of　green
cheese：　that　is　an　hypothesis。　　But　another　man；　who　has　devoted　a
great　deal　of　time　and　attention　to　the　subject；　and　availed　himself　of
the　most　powerful　telescopes　and　the　results　of　the　observations　of
others；　declares　that　in　his　opinion　it　is　probably　composed　of
materials　very　similar　to　those　of　which　our　own　earth　is　made　up：　and
that　is　also　only　an　hypothesis。　　But　I　need　not　tell　you　that　there　is
an　enormous　difference　in　the　value　of　the　two　hypotheses。　　That　one
which　is　based　on　sound　scientific　knowledge　is　sure　to　have　a
corresponding　value；　and　that　which　is　a　mere　hasty　random　guess　is
likely　to　have　but　little　value。　　Every　great　step　in　our　progress　in
discovering　causes　has　been　made　in　exactly　the　same　way　as　that　which　I
have　detailed　to　you。　　A　person　observing　the　occurrence　of　certain
facts　and　phenomena　asks；　naturally　enough；　what　process；　what　kind　of
operation　known　to　occur　in　nature　applied　to　the　particular　case；　will
unravel　and　explain　the　mystery？　　Hence　you　have　the　scientific
hypothesis；　and　its　value　will　be　proportionate　to　the　care　and
completeness　with　which　its　basis　had　been　tested　and　verified。　　It　is
in　these　matters　as　in　the　commonest　affairs　of　practical　life：　the
guess　of　the　fool　will　be　folly；　while　the　guess　of　the　wise　man　will
contain　wisdom。　　In　all　cases；　you　see　that　the　value　of　the　result
depends　on　the　patience　and　faithfulness　with　which　the　investigator
applies　to　his　hypothesis　every　possible　kind　of　verification。

I　dare　say　I　may　have　to　return　to　this　point　by…and…by；　but　having
dealt　thus　far　with　our　logical　methods；　I　must　now　turn　to　something
which；　perhaps；　you　may　consider　more　interesting；　or；　at　any　rate；
more　tangible。　　But　in　reality　there　are　but　few　things　that　can　be
more　important　for　you　to　understand　than　the　mental　processes　and　the
means　by　which　we　obtain　scientific　conclusions　and　theories。1　　Having
granted　that　the　inquiry　is　a　proper　one；　and　having　determined　on　the
nature　of　the　methods　we　are　to　pursue　and　which　only　can　lead　to
success；　I　must　now　turn　to　the　consideration　of　our　knowledge　of　the
nature　of　the　processes　which　have　resulted　in　the　present　condition　of
organic　nature。

Here；　let　me　say　at　once；　lest　some　of　you　misunderstand　me；　that　I　have
extremely　little　to　report。　　The　question　of　how　the　present　condition
of　organic　nature　came　about；　resolves　itself　into　two　questions。　　The
first　is：　How　has　organic　or　living　matter　commenced　its　existence？　And
the　second　is：　How　has　it　been　perpetuated？　　On　the　second　question　I
shall　have　more　to　say　hereafter。　　But　on　the　first　one；　what　I　now
have　to　say　will　be　for　the　most　part　of　a　negative　character。

If　you　consider　what　kind　of　evidence　we　can　have　upon　this　matter；　it
will　resolve　itself　into　two　kinds。　　We　may　have　historical　evidence
and　we　may　have　experimental　evidence。　　It　is；　for　example；
conceivable；　that　inasmuch　as　the　hardened　mud　which　forms　a
considerable　portion　of　the　thickness　of　the　earth's　crust　contains
faithful　records　of　the　past　forms　of　life；　and　inasmuch　as　these
differ　more　and　more　as　we　go　further　down；it　is　possible　and
conceivable　that　we　might　come　to　some　particular　bed　or　stratum　which
should　contain　the　remains　of　those　creatures　with　which　organic　life
began　upon　the　earth。　　And　if　we　did　so；　and　if　such　forms　of　organic
life　were　preservable；　we　should　have　what　I　would　call　historical
evidence　of　the　mode　in　which　organic　life　began　upon　this　planet。　　Many
persons　will　tell　you；　and　indeed　you　will　find　it　stated　in　many　works
on　geology；　that　this　has　been　done；　and　that　we　really　possess　such　a
record；　there　are　some　who　imagine　that　the　earliest　forms　of　life　of
which　we　have　as　yet　discovered　any　record；　are　in　truth　the　forms　in
which　animal　life　began　upon　the　globe。　　The　grounds　on　which　they　base
that　supposition　are　these：That　if　you　go　through　the　enormous
thickness　of　the　earth's　crust　and　get　down　to　the　older　rocks；　the
higher　vertebrate　animalsthe　quadrupeds；　birds；　and　fishescease　to
be　found；　beneath　them　you　find　only　the　invertebrate　animals；　and　in
the　deepest　and　lowest　rocks　those　remains　become　scantier　and
scantier；　not　in　any　very　gradual　progression；　however；　until；　at
length；　in　what　are　supposed　to　be　the　oldest　rocks；　the　animal　remains
which　are　found　are　almost　always　confined　to　four　forms'Oldhamia'；
whose　precise　nature　is　not　known；　whether　plant　or　animal；　'Lingula'；
a　kind　of　mollusc；　'Trilobites'；　a　crustacean　animal；　having　the　same
essential　plan　of　construction；　though　differing　in　many　details　from　a
lobster　or　crab；　and　Hymenocaris；　which　is　also　a　crustacean。　　So　that
you　have　all　the　'Fauna'　reduced；　at　this　period；　to　four　forms：　one　a
kind　of　animal　or　plant　that　we　know　nothing　about；　and　three　undoubted
animalstwo　crustaceans　and　one　mollusc。

I　think；　considering　the　organization　of　these　mollusca　and　crustacea；
and　looking　at　their　very　complex　nature；　that　it　does　indeed　require　a
very　strong　imagination　to　conceive　that　these　were　the　first　created
of　all　living　things。　　And　you　must　take　into　consideration　the　fact
that　we　have　not　the　slightest　proof　that　these　which　we　call　the
oldest　beds　are　really　so：　I　repeat；　we　have　not　the　slightest　proof　of
it。　　When　you　find　in　some　places　that　in　an　enormous　thickness　of
rocks　there　are　but　very　scanty　traces　of　life；　or　absolutely　none　at
all；　and　that　in　other　parts　of　the　world　rocks　of　the　very　same
formation　are　crowded　with　the　records　of　living　forms；　I　think　it　is
impossible　to　place　any　reliance　on　the　supposition；　or　to　feel　oneself
justified　in　supposing　that　these　are　the　forms　in　which　life　first
commenced。　　I　have　not　time　here　to　enter　upon　the　technical　grounds
upon　which　I　am　led　to　this　conclusion；that　could　hardly　be　done
properly　in　half　a　dozen　lectures　on　that　part　alone；I　must　content
myself　with　saying　that　I　do　not　at　all　believe　that　these　are　the
oldest　forms　of　life。

I　turn　to　the　experimental　side　to　see　what　evidence　we　have　there。　　To
enable　us　to　say　that　we　know　anything　about　the　experimental
origination　of　organization　and　life；　the　investigator　ought　to　be　able
to　take　inorganic　matters；　such　as　carbonic　acid；　ammonia；　water；　and
salines；　in　any　sort　of　inorganic　combination；　and　be　able　to　build
them　up　into　Protein　matter；　and　that　that　Protein　matter　ought　to
begin　to　live　in　an　organic　form。　　That；　nobody　has　done　as　yet；　and　I
suspect　it　will　be　a　long　while　before　anybody　does　do　it。　　But　the
thing　is　by　no　means　so　impossible　as　it　looks；　for　the　researches　of
modern　chemistry　have　shown　usI　won't　say　the　road　towards　it；　but；
if　I　may　so　say；　they　have　shown　the　finger…post　pointing　to　the　road
that　may　lead　to　it。

It　is　not　many　years　agoand　you　must　recollect　that　Organic　Chemistry
is　a　young　science；　not　above　a　couple　of　generations　old；you　must
not　expect　too　much　of　it；　it　is　not　many　years　ago　since　it　was　said
to　be　perfectly　impossible　to　fabricate　any　organic　compound；　that　is
to　say；　any　non…mineral　compound　which　is　to　be　found　in　an　organized
being。　　It　remained　so　for　a　very　long　period；　but　it　is　now　a
considerable　number　of　years　since　a　distinguished　foreign　chemist
contrived　to　fabricate　Urea；　a　substance　of　a　very　complex　character；
which　forms　one　of　the　waste　products　of　animal　structures。　　And　of
late　years　a　number　of　other　compounds；　such　as　Butyric　Acid；　and
others；　have　been　added　to　the　list。　　I　need　not　tell　you　that
chemistry　is　an　enormous　distance　from　the　goal　I　indicate；　all　I　wish
to　point　out　to　you　is；　that　it　is　by　no　means　safe　to　say　that　that
goal　may　not　be　reached　one　day。　　It　may　be　that　it　is　impossible　for
us　to　produce　the　conditions　requisite　to　the　origination　of　life；　but
we　must　speak　modestly　about　the　matter；　and　recollect　that　Science　has
put　her　foot　upon　the　bottom　round　of　the　ladder。　　Truly　he　would　be　a
bold　man　who　would　venture　to　predict　where　she　will　be　fifty　years
hence。

There　is　another　inquiry　which　bears　indirectly　upon　this　question；　and
upon　which　I　must　say　a　few　words。　　You　are　all　of　you　aware　of　the
phenomena　of　what　is　called　spontaneous　generation。　　Our　forefathers；
down　to　the　seventeenth　century；　or　thereabouts；　all　imagined；　in
perfectly　good　faith；　that　certain　vegetable　and　animal　forms　gave
birth；　in　the　process　of　their　decomposition；　to　insect　life。　　Thus；　if
you　put　a　piece　of　meat　in　the　sun；　and　allowed　it　to　putrefy；　they
conceived　that　the　grubs　which　soon　began　to　appear　were　the　result　of
the　action　of　a　power　of　spontaneous　generation　which　the　meat
contained。　　And　they　could　give　you　receipts　for　making　various　animal
and　vegetable　preparations　which　would　produce　particular　kinds　of
animals。　　A　very　distinguished　Italian　naturalist；　named　Redi；　took　up
the　question；　at　a　time　when　everybody　believed　in　it；　among　others　our
own　great　Harvey；　the　discoverer　of　the　circulation　of　the　blood。　　You
will　constantly　find　his　name　quoted；　however；　as　an　opponent　of　the
doctrine　of　spontaneous　generation；　but　the　fact　is；　and　you　will　see　it
if　you　will　take　the　trouble　to　look　into　his　works；　Harvey　believed　it
as　profoundly　as　any　man　of　his　time；　but　he　happened　to　enunciate　a
very　curious　propositionthat　every　living　thing　came　from　an　'egg'；
he　did　not　mean　to　use　the　word　in　the　sense　in　which　we　now　employ　it；
he　only　meant　to　say　that　every　living　thing　originated　in　a　little
rounded　particle　of　organized　substance；　and　it　is　from　this
circumstance；　probably；　that　the　notion　of　Harvey　having　opposed　the
doctrine　originated。　　Then　came　Redi；　and　he　proceeded　to　upset　the
doctrine　in　a　very　simple　manner。　　He　merely　covered　the　piece　of　meat
with　some　very　fine　gauze；　and　then　he　exposed　it　to　the　same
conditions。　　The　result　of　this　was　that　no　grubs　or　insects　were
produced；　he　proved　that　the　grubs　originated　from　the　insects　who　came
and　deposited　their　eggs　in　the　meat；　and　that　they　were　hatched　by　the
heat　of　the　sun。　　By　this　kind　of　inquiry　he　thoroughly　upset　the
doctrine　of　spontaneous　generation；　for　his　time　at　least。

Then　came　the　discovery　and　application　of　the　microscope　to　scientific
inquiries；　which　showed　to　naturalists　that　besides　the　organisms　which
they　already　knew　as　living　beings　and　plants；　there　were　an　immense
number　of　minute　things　which　could　be　obtained　apparently　almost　at
will　from　decaying　vegetable　and　animal　forms。　　Thus；　if　you