Noorderoffishesisknowntobeextinct。Everyfishthatwefindinthestrata——towhichIhavebeenreferring——canbeidentifiedandplacedinoneoftheorderswhichexistatthepresentday。Thereisnotknowntobeasingleordinalformofinsectextinct。Thereareonlytwoordersextinctamongthe’Crustacea’。Thereisnotknowntobeanextinctorderofthesecreatures，theparasiticandotherworms。

buttherearetwo，nottosaythree，absolutelyextinctordersofthisclass，the’Echinodermata’。outofalltheordersofthe’Coelenterata’

and’Protozoa’onlyone，theRugoseCorals。

Sothat，yousee，outofsomewhereabout120ordersofanimals，takingthemaltogether，youwillnot，attheoutsideestimate，findabovetenoradozenextinct。Summingupalltheordersofanimalswhichhaveleftremainsbehindthem，youwillnotfindabovetenoradozenwhichcannotbearrangedwiththoseofthepresentday。thatistosay，thatthedifferencedoesnotamounttomuchmorethantenpercent。：andtheproportionofextinctordersofplantsisstillsmaller。Ithinkthatthatisaveryastounding，amostastonishingfact，seeingtheenormousepochsoftimewhichhaveelapsedduringtheconstitutionofthesurfaceoftheearthasitatpresentexists。itis，indeed，amostastoundingthingthattheproportionofextinctordinaltypesshouldbesoexceedinglysmall。

Butnow，thereisanotherpointofviewinwhichwemustlookatthispastcreation。Supposethatweweretosinkaverticalpitthroughthefloorbeneathus，andthatIcouldsucceedinmakingasectionrightthroughinthedirectionofNewZealand，IshouldfindineachofthedifferentbedsthroughwhichIpassedtheremainsofanimalswhichI

shouldfindinthatstratumandnotintheothers。First，Ishouldcomeuponbedsofgravelordriftcontainingthebonesoflargeanimals，suchastheelephant，rhinoceros，andcavetiger。RathercuriousthingstofallacrossinPiccadilly！IfIshoulddiglowerstill，IshouldcomeuponabedofwhatwecalltheLondonclay，andinthis，asyouwillseeinourgalleriesupstairs，arefoundremainsofstrangecattle，remainsofturtles，palms，andlargetropicalfruits。

withshell-fishsuchasyouseethelikeofnowonlyintropicalregions。IfIwentbelowthat，Ishouldcomeuponthechalk，andthereIshouldfindsomethingaltogetherdifferent，theremainsofichthyosauriandpterodactyles，andammonites，andsoforth。

IdonotknowwhatMr。GodwinAustinwouldsaycomesnext，butprobablyrockscontainingmoreammonites，andmoreichthyosauriandplesiosauri，withavastnumberofotherthings。andunderthatIshouldmeetwithyetolderrocks，containingnumbersofstrangeshellsandfishes。andinthuspassingfromthesurfacetothelowestdepthsoftheearth’scrust，theformsofanimallifeandvegetablelifewhichIshouldmeetwithinthesuccessivebedswould，lookingatthembroadly，bethemoredifferentthefurtherthatIwentdown。Or，inotherwords，inasmuchaswestartedwiththeclearprinciple，thatinaseriesofnaturally-disposedmudbedsthelowestaretheoldest，weshouldcometothisresult，thatthefurtherwegobackintimethemoredifferenceexistsbetweentheanimalandvegetablelifeofanepochandthatwhichnowexists。ThatwastheconclusiontowhichIwishedtobringyouattheendofthisLecture。

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THEMETHODBYWHICVHTHECAUSESOFTHEPRESENTANDPASTCONDITIONSOF

ORGANICNATUREARETOBEDISCOVERED——THEORIGINATIONOFLIVINGBEINGS

InthetwoprecedinglecturesIhaveendeavouredtoindicatetoyoutheextentofthesubject-matteroftheinquiryuponwhichweareengaged。

andnow，havingthusacquiredsomeconceptionofthePastandPresentphenomenaofOrganicNature，Imustnowturntothatwhichconstitutesthegreatproblemwhichwehavesetbeforeourselves——Imean，thequestionofwhatknowledgewehaveofthecausesofthesephenomenaoforganicnature，andhowsuchknowledgeisobtainable。

Here，onthethresholdoftheinquiry，anobjectionmeetsus。Thereareintheworldanumberofextremelyworthy，well-meaningpersons，whosejudgmentsandopinionsareentitledtotheutmostrespectonaccountoftheirsincerity，whoareofopinionthatVitalPhenomena，andespeciallyallquestionsrelatingtotheoriginofvitalphenomena，arequestionsquiteapartfromtheordinaryrunofinquiry，andare，bytheirverynature，placedoutofourreach。Theysaythatallthesephenomenaoriginatedmiraculously，orinsomewaytotallydifferentfromtheordinarycourseofnature，andthatthereforetheyconceiveittobefutile，nottosaypresumptuous，toattempttoinquireintothem。

Tosuchsincereandearnestpersons，Iwouldonlysay，thataquestionofthiskindisnottobeshelvedupontheoreticalorspeculativegrounds。YoumayrememberthestoryoftheSophistwhodemonstratedtoDiogenesinthemostcompleteandsatisfactorymannerthathecouldnotwalk。that，infact，allmotionwasanimpossibility。andthatDiogenesrefutedhimbysimplygettingupandwalkingroundhistub。So，inthesameway，themanofsciencerepliestoobjectionsofthiskind，bysimplygettingupandwalkingonward，andshowingwhatsciencehasdoneandisdoing——bypointingtothatimmensemassoffactswhichhavebeenascertainedandsystematizedundertheformsofthegreatdoctrinesofMorphology，ofDevelopment，ofDistribution，andthelike。Heseesanenormousmassoffactsandlawsrelatingtoorganicbeings，whichstandonthesamegoodsoundfoundationaseveryothernaturallaw。andtherefore，withthismassoffactsandlawsbeforeus，therefore，seeingthat，asfarasorganicmattershavehithertobeenaccessibleandstudied，theyhaveshownthemselvescapableofyieldingtoscientificinvestigation，wemayacceptthisasproofthatorderandlawreignthereaswellasintherestofnature。andthemanofsciencesaysnothingtoobjectorsofthissort，butsupposesthatwecanandshallwalktoaknowledgeoftheoriginoforganicnature，inthesamewaythatwehavewalkedtoaknowledgeofthelawsandprinciplesoftheinorganicworld。

Butthereareobjectorswhosaythesamefromignoranceandill-will。

TosuchIwouldreplythattheobjectioncomesillfromthem，andthattherealpresumption，Imayalmostsaytherealblasphemy，inthismatter，isintheattempttolimitthatinquiryintothecausesofphenomenawhichisthesourceofallhumanblessings，andfromwhichhassprungallhumanprosperityandprogress。for，afterall，wecanaccomplishcomparativelylittle。thelimitedrangeofourownfacultiesboundsusoneveryside，——thefieldofourpowersofobservationissmallenough，andhewhoendeavourstonarrowthesphereofourinquiriesisonlypursuingacoursethatislikelytoproducethegreatestharmtohisfellow-men。

Butnow，assuming，aswealldo，Ihope，thatthesephenomenaareproperlyaccessibletoinquiry，andsettingoutuponoursearchintothecausesofthephenomenaoforganicnature，or，atanyrate，settingouttodiscoverhowmuchweatpresentknowupontheseabstrusematters，thequestionarisesastowhatistobeourcourseofproceeding，andwhatmethodwemustlaydownforourguidance。Ireplytothatquestion，thatourmethodmustbeexactlythesameasthatwhichispursuedinanyotherscientificinquiry，themethodofscientificinvestigationbeingthesameforallordersoffactsandphenomenawhatsoever。

Imustdwellalittleonthispoint，forIwishyoutoleavethisroomwithaveryclearconvictionthatscientificinvestigationisnot，asmanypeopleseemtosuppose，somekindofmodernblackart。Isaythatyoumighteasilygatherthisimpressionfromthemannerinwhichmanypersonsspeakofscientificinquiry，ortalkaboutinductiveanddeductivephilosophy，ortheprinciplesoftheBaconianphilosophy。I

doprotestthat，ofthevastnumberofcantsinthisworld，therearenone，tomymind，socontemptibleasthepseudoscientificcantwhichistalkedabouttheBaconianphilosophy。

TohearpeopletalkaboutthegreatChancellor——andaverygreatmanhecertainlywas，——youwouldthinkthatitwashewhohadinventedscience，andthattherewasnosuchthingassoundreasoningbeforethetimeofQueenElizabeth。Ofcourseyousay，thatcannotpossiblybetrue。youperceive，onamoment’sreflection，thatsuchanideaisabsurdlywrong，andyet，sofirmlyrootedisthissortofimpression，——Icannotcallitanidea，orconception，——thethingistooabsurdtobeentertained，——butsocompletelydoesitexistatthebottomofmostmen’sminds，thatthishasbeenamatterofobservationwithmeformanyyearspast。Therearemanymenwho，thoughknowingabsolutelynothingofthesubjectwithwhichtheymaybedealing，wish，nevertheless，todamagetheauthorofsomeviewwithwhichtheythinkfittodisagree。Whattheydo，then，isnottogoandlearnsomethingaboutthesubject，whichonewouldnaturallythinkthebestwayoffairlydealingwithit。buttheyabusetheoriginatoroftheviewtheyquestion，inageneralmanner，andwindupbysayingthat，Afterall，youknow，theprinciplesandmethodofthisauthoraretotallyopposedtothecanonsoftheBaconianphilosophy。Theneverybodyapplauds，asamatterofcourse，andagreesthatitmustbeso。Butifyouweretostopthemallinthemiddleoftheirapplause，youwouldprobablyfindthatneitherthespeakernorhisapplauderscouldtellyouhoworinwhatwayitwasso。neithertheonenortheotherhavingtheslightestideaofwhattheymeanwhentheyspeakoftheBaconianphilosophy。

Youwillunderstand，Ihope，thatIhavenottheslightestdesiretojoinintheoutcryagainsteitherthemorals，theintellect，orthegreatgeniusofLordChancellorBacon。Hewasundoubtedlyaverygreatman，letpeoplesaywhattheywillofhim。butnotwithstandingallthathedidforphilosophy，itwouldbeentirelywrongtosupposethatthemethodsofmodernscientificinquiryoriginatedwithhim，orwithhisage。theyoriginatedwiththefirstman，whoeverhewas。andindeedexistedlongbeforehim，formanyoftheessentialprocessesofreasoningareexertedbythehigherorderofbrutesascompletelyandeffectivelyasbyourselves。Weseeinmanyofthebrutecreationtheexerciseofone，atleast，ofthesamepowersofreasoningasthatwhichweourselvesemploy。

Themethodofscientificinvestigationisnothingbuttheexpressionofthenecessarymodeofworkingofthehumanmind。Itissimplythemodeatwhichallphenomenaarereasonedabout，renderedpreciseandexact。

Thereisnomoredifference，butthereisjustthesamekindofdifference，betweenthementaloperationsofamanofscienceandthoseofanordinaryperson，asthereisbetweentheoperationsandmethodsofabakerorofabutcherweighingouthisgoodsincommonscales，andtheoperationsofachemistinperformingadifficultandcomplexanalysisbymeansofhisbalanceandfinely-graduatedweights。Itisnotthattheactionofthescalesintheonecase，andthebalanceintheother，differintheprinciplesoftheirconstructionormannerofworking。butthebeamofoneissetonaninfinitelyfineraxisthantheother，andofcourseturnsbytheadditionofamuchsmallerweight。

Youwillunderstandthisbetter，perhaps，ifIgiveyousomefamiliarexample。Youhaveallhearditrepeated，Idaresay，thatmenofscienceworkbymeansofInductionandDeduction，andthatbythehelpoftheseoperations，they，inasortofsense，wringfromNaturecertainotherthings，whicharecalledNaturalLaws，andCauses，andthatoutofthese，bysomecunningskilloftheirown，theybuildupHypothesesandTheories。Anditisimaginedbymany，thattheoperationsofthecommonmindcanbebynomeanscomparedwiththeseprocesses，andthattheyhavetobeacquiredbyasortofspecialapprenticeshiptothecraft。Tohearalltheselargewords，youwouldthinkthatthemindofamanofsciencemustbeconstituteddifferentlyfromthatofhisfellowmen。butifyouwillnotbefrightenedbyterms，youwilldiscoverthatyouarequitewrong，andthatalltheseterribleapparatusarebeingusedbyyourselveseverydayandeveryhourofyourlives。

Thereisawell-knownincidentinoneofMoliere’splays，wheretheauthormakestheheroexpressunboundeddelightonbeingtoldthathehadbeentalkingproseduringthewholeofhislife。Inthesameway，Itrust，thatyouwilltakecomfort，andbedelightedwithyourselves，onthediscoverythatyouhavebeenactingontheprinciplesofinductiveanddeductivephilosophyduringthesameperiod。Probablythereisnotoneherewhohasnotinthecourseofthedayhadoccasiontosetinmotionacomplextrainofreasoning，oftheverysamekind，thoughdifferingofcourseindegree，asthatwhichascientificmangoesthroughintracingthecausesofnaturalphenomena。

Averytrivialcircumstancewillservetoexemplifythis。Supposeyougointoafruiterer’sshop，wantinganapple，——youtakeupone，and，onbitingit，youfinditissour。youlookatit，andseethatitishardandgreen。Youtakeupanotherone，andthattooishard，green，andsour。Theshopmanoffersyouathird。but，beforebitingit，youexamineit，andfindthatitishardandgreen，andyouimmediatelysaythatyouwillnothaveit，asitmustbesour，likethosethatyouhavealreadytried。

Nothingcanbemoresimplethanthat，youthink。butifyouwilltakethetroubletoanalyzeandtraceoutintoitslogicalelementswhathasbeendonebythemind，youwillbegreatlysurprised。Inthefirstplace，youhaveperformedtheoperationofInduction。Youfoundthat，intwoexperiences，hardnessandgreennessinapplesgotogetherwithsourness。Itwassointhefirstcase，anditwasconfirmedbythesecond。True，itisaverysmallbasis，butstillitisenoughtomakeaninductionfrom。yougeneralizethefacts，andyouexpecttofindsournessinappleswhereyougethardnessandgreenness。Youfounduponthatagenerallaw，thatallhardandgreenapplesaresour。andthat，sofarasitgoes，isaperfectinduction。Well，havinggotyournaturallawinthisway，whenyouareofferedanotherapplewhichyoufindishardandgreen，yousay，Allhardandgreenapplesaresour。

thisappleishardandgreen，thereforethisappleissour。Thattrainofreasoningiswhatlogicianscallasyllogism，andhasallitsvariouspartsandterms，——itsmajorpremiss，itsminorpremiss，anditsconclusion。And，bythehelpoffurtherreasoning，which，ifdrawnout，wouldhavetobeexhibitedintwoorthreeothersyllogisms，youarriveatyourfinaldetermination，Iwillnothavethatapple。Sothat，yousee，youhave，inthefirstplace，establishedalawbyInduction，anduponthatyouhavefoundedaDeduction，andreasonedoutthespecialconclusionoftheparticularcase。Wellnow，suppose，havinggotyourlaw，thatatsometimeafterwards，youarediscussingthequalitiesofappleswithafriend：youwillsaytohim，Itisaverycuriousthing，——butIfindthatallhardandgreenapplesaresour！Yourfriendsaystoyou，Buthowdoyouknowthat？Youatoncereply，Oh，becauseIhavetrieditoverandoveragain，andhavealwaysfoundthemtobeso。Well。ifweweretalkingscienceinsteadofcommonsense，weshouldcallthatanExperimentalVerification。And，ifstillopposed，yougofurther，andsay，IhaveheardfromthepeopleinSomersetshireandDevonshire，wherealargenumberofapplesaregrown，thattheyhaveobservedthesamething。ItisalsofoundtobethecaseinNormandy，andinNorthAmerica。Inshort，Ifindittobetheuniversalexperienceofmankindwhereverattentionhasbeendirectedtothesubject。Whereupon，yourfriend，unlessheisaveryunreasonableman，agreeswithyou，andisconvincedthatyouarequiterightintheconclusionyouhavedrawn。Hebelieves，althoughperhapshedoesnotknowhebelievesit，thatthemoreextensiveVerificationsare，——thatthemorefrequentlyexperimentshavebeenmade，andresultsofthesamekindarrivedat，——thatthemorevariedtheconditionsunderwhichthesameresultshavebeenattained，themorecertainistheultimateconclusion，andhedisputesthequestionnofurther。Heseesthattheexperimenthasbeentriedunderallsortsofconditions，astotime，place，andpeople，withthesameresult。andhesayswithyou，therefore，thatthelawyouhavelaiddownmustbeagoodone，andhemustbelieveit。

Insciencewedothesamething——thephilosopherexercisespreciselythesamefaculties，thoughinamuchmoredelicatemanner。Inscientificinquiryitbecomesamatterofdutytoexposeasupposedlawtoeverypossiblekindofverification，andtotakecare，moreover，thatthisisdoneintentionally，andnotlefttoamereaccident，asinthecaseoftheapples。Andinscience，asincommonlife，ourconfidenceinalawisinexactproportiontotheabsenceofvariationintheresultofourexperimentalverifications。Forinstance，ifyouletgoyourgraspofanarticleyoumayhaveinyourhand，itwillimmediatelyfalltotheground。Thatisaverycommonverificationofoneofthebestestablishedlawsofnature——thatofgravitation。Themethodbywhichmenofscienceestablishtheexistenceofthatlawisexactlythesameasthatbywhichwehaveestablishedthetrivialpropositionaboutthesournessofhardandgreenapples。Butwebelieveitinsuchanextensive，thorough，andunhesitatingmannerbecausetheuniversalexperienceofmankindverifiesit，andwecanverifyitourselvesatanytime。andthatisthestrongestpossiblefoundationonwhichanynaturallawcanrest。

Somuchbywayofproofthatthemethodofestablishinglawsinscienceisexactlythesameasthatpursuedincommonlife。Letusnowturntoanothermatter(thoughreallyitisbutanotherphaseofthesamequestion)，andthatis，themethodbywhich，fromtherelationsofcertainphenomena，weprovethatsomestandinthepositionofcausestowardstheothers。

Iwanttoputthecaseclearlybeforeyou，andIwillthereforeshowyouwhatImeanbyanotherfamiliarexample。Iwillsupposethatoneofyou，oncomingdowninthemorningtotheparlourofyourhouse，findsthatatea-potandsomespoonswhichhadbeenleftintheroomonthepreviouseveningaregone，——thewindowisopen，andyouobservethemarkofadirtyhandonthewindow-frame，andperhaps，inadditiontothat，younoticetheimpressofahob-nailedshoeonthegraveloutside。Allthesephenomenahavestruckyourattentioninstantly，andbeforetwominuteshavepassedyousay，Oh，somebodyhasbrokenopenthewindow，enteredtheroom，andrunoffwiththespoonsandthetea-pot！Thatspeechisoutofyourmouthinamoment。Andyouwillprobablyadd，I

knowtherehas。Iamquitesureofit！Youmeantosayexactlywhatyouknow。butinrealitywhatyouhavesaidhasbeentheexpressionofwhatis，inallessentialparticulars，anHypothesis。Youdonot’know’

itatall。itisnothingbutanhypothesisrapidlyframedinyourownmind！Anditisanhypothesisfoundedonalongtrainofinductionsanddeductions。

Whatarethoseinductionsanddeductions，andhowhaveyougotatthishypothesis？Youhaveobserved，inthefirstplace，thatthewindowisopen。butbyatrainofreasoninginvolvingmanyInductionsandDeductions，youhaveprobablyarrivedlongbeforeattheGeneralLaw——andaverygoodoneitis——thatwindowsdonotopenofthemselves。

andyouthereforeconcludethatsomethinghasopenedthewindow。A

secondgenerallawthatyouhavearrivedatinthesamewayis，thattea-potsandspoonsdonotgooutofawindowspontaneously，andyouaresatisfiedthat，astheyarenotnowwhereyouleftthem，theyhavebeenremoved。Inthethirdplace，youlookatthemarksonthewindow-sill，andtheshoemarksoutside，andyousaythatinallpreviousexperiencetheformerkindofmarkhasneverbeenproducedbyanythingelsebutthehandofahumanbeing。andthesameexperienceshowsthatnootheranimalbutmanatpresentwearsshoeswithhob-nailsonthemsuchaswouldproducethemarksinthegravel。Idonotknow，evenifwecoulddiscoveranyofthosemissinglinksthataretalkedabout，thattheywouldhelpustoanyotherconclusion！Atanyratethelawwhichstatesourpresentexperienceisstrongenoughformypresentpurpose——Younextreachtheconclusion，thatasthesekindsofmarkshavenotbeenleftbyanyotheranimalsthanmen，orareliabletobeformedinanyotherwaythanbyaman’shandandshoe，themarksinquestionhavebeenformedbyamaninthatway。Youhave，further，agenerallaw，foundedonobservationandexperience，andthat，too，is，Iamsorrytosay，averyuniversalandunimpeachableone，——thatsomemenarethieves。andyouassumeatoncefromallthesepremisses——andthatiswhatconstitutesyourhypothesis——thatthemanwhomadethemarksoutsideandonthewindow-sill，openedthewindow，gotintotheroom，andstoleyourtea-potandspoons。Youhavenowarrivedata’VeraCausa’——youhaveassumedaCausewhichitisplainiscompetenttoproduceallthephenomenayouhaveobserved。Youcanexplainallthesephenomenaonlybythehypothesisofathief。Butthatisahypotheticalconclusion，ofthejusticeofwhichyouhavenoabsoluteproofatall。itisonlyrenderedhighlyprobablebyaseriesofinductiveanddeductivereasonings。

Isupposeyourfirstaction，assumingthatyouareamanofordinarycommonsense，andthatyouhaveestablishedthishypothesistoyourownsatisfaction，willverylikelybetogooffforthepolice，andsetthemonthetrackoftheburglar，withtheviewtotherecoveryofyourproperty。Butjustasyouarestartingwiththisobject，somepersoncomesin，andonlearningwhatyouareabout，says，Mygoodfriend，youaregoingonagreatdealtoofast。Howdoyouknowthatthemanwhoreallymadethemarkstookthespoons？Itmighthavebeenamonkeythattookthem，andthemanmayhavemerelylookedinafterwards。Youwouldprobablyreply，Well，thatisallverywell，butyouseeitiscontrarytoallexperienceofthewaytea-potsandspoonsareabstracted。sothat，atanyrate，yourhypothesisislessprobablethanmine。Whileyouaretalkingthethingoverinthisway，anotherfriendarrives，oneofthatgoodkindofpeoplethatIwastalkingofalittlewhileago。Andhemightsay，Oh，mydearsir，youarecertainlygoingonagreatdealtoofast。Youaremostpresumptuous。Youadmitthatalltheseoccurrencestookplacewhenyouwerefastasleep，atatimewhenyoucouldnotpossiblyhaveknownanythingaboutwhatwastakingplace。HowdoyouknowthatthelawsofNaturearenotsuspendedduringthenight？Itmaybethattherehasbeensomekindofsupernaturalinterferenceinthiscase。Inpointoffact，hedeclaresthatyourhypothesisisoneofwhichyoucannotatalldemonstratethetruth，andthatyouarebynomeanssurethatthelawsofNaturearethesamewhenyouareasleepaswhenyouareawake。

Well，now，youcannotatthemomentanswerthatkindofreasoning。Youfeelthatyourworthyfriendhasyousomewhatatadisadvantage。Youwillfeelperfectlyconvincedinyourownmind，however，thatyouarequiteright，andyousaytohim，Mygoodfriend，Icanonlybeguidedbythenaturalprobabilitiesofthecase，andifyouwillbekindenoughtostandasideandpermitmetopass，Iwillgoandfetchthepolice。

Well，wewillsupposethatyourjourneyissuccessful，andthatbygoodluckyoumeetwithapoliceman。thateventuallytheburglarisfoundwithyourpropertyonhisperson，andthemarkscorrespondtohishandandtohisboots。Probablyanyjurywouldconsiderthosefactsaverygoodexperimentalverificationofyourhypothesis，touchingthecauseoftheabnormalphenomenaobservedinyourparlour，andwouldactaccordingly。

Now，inthissuppositiouscase，Ihavetakenphenomenaofaverycommonkind，inorderthatyoumightseewhatarethedifferentstepsinanordinaryprocessofreasoning，ifyouwillonlytakethetroubletoanalyseitcarefully。AlltheoperationsIhavedescribed，youwillsee，areinvolvedinthemindofanymanofsenseinleadinghimtoaconclusionastothecourseheshouldtakeinordertomakegoodarobberyandpunishtheoffender。Isaythatyouareled，inthatcase，toyourconclusionbyexactlythesametrainofreasoningasthatwhichamanofsciencepursueswhenheisendeavouringtodiscovertheoriginandlawsofthemostoccultphenomena。Theprocessis，andalwaysmustbe，thesame。andpreciselythesamemodeofreasoningwasemployedbyNewtonandLaplaceintheirendeavourstodiscoveranddefinethecausesofthemovementsoftheheavenlybodies，asyou，withyourowncommonsense，wouldemploytodetectaburglar。Theonlydifferenceis，thatthenatureoftheinquirybeingmoreabstruse，everystephastobemostcarefullywatched，sothattheremaynotbeasinglecrackorflawinyourhypothesis。Aflaworcrackinmanyofthehypothesesofdailylifemaybeoflittleornomomentasaffectingthegeneralcorrectnessoftheconclusionsatwhichwemayarrive。but，inascientificinquiry，afallacy，greatorsmall，isalwaysofimportance，andissuretobeconstantlyproductiveofmischievous，ifnotfatalresults。

Donotallowyourselvestobemisledbythecommonnotionthatanhypothesisisuntrustworthysimplybecauseitisanhypothesis。Itisoftenurged，inrespecttosomescientificconclusion，that，afterall，itisonlyanhypothesis。Butwhatmorehavewetoguideusinnine-tenthsofthemostimportantaffairsofdailylifethanhypotheses，andoftenveryill-basedones？Sothatinscience，wheretheevidenceofanhypothesisissubjectedtothemostrigidexamination，wemayrightlypursuethesamecourse。Youmayhavehypothesesandhypotheses。Amanmaysay，ifhelikes，thatthemoonismadeofgreencheese：thatisanhypothesis。Butanotherman，whohasdevotedagreatdealoftimeandattentiontothesubject，andavailedhimselfofthemostpowerfultelescopesandtheresultsoftheobservationsofothers，declaresthatinhisopinionitisprobablycomposedofmaterialsverysimilartothoseofwhichourownearthismadeup：andthatisalsoonlyanhypothesis。ButIneednottellyouthatthereisanenormousdifferenceinthevalueofthetwohypotheses。Thatonewhichisbasedonsoundscientificknowledgeissuretohaveacorrespondingvalue。andthatwhichisamerehastyrandomguessislikelytohavebutlittlevalue。EverygreatstepinourprogressindiscoveringcauseshasbeenmadeinexactlythesamewayasthatwhichI

havedetailedtoyou。Apersonobservingtheoccurrenceofcertainfactsandphenomenaasks，naturallyenough，whatprocess，whatkindofoperationknowntooccurinnatureappliedtotheparticularcase，willunravelandexplainthemystery？Henceyouhavethescientifichypothesis。anditsvaluewillbeproportionatetothecareandcompletenesswithwhichitsbasishadbeentestedandverified。Itisinthesemattersasinthecommonestaffairsofpracticallife：theguessofthefoolwillbefolly，whiletheguessofthewisemanwillcontainwisdom。Inallcases，youseethatthevalueoftheresultdependsonthepatienceandfaithfulnesswithwhichtheinvestigatorappliestohishypothesiseverypossiblekindofverification。

IdaresayImayhavetoreturntothispointby-and-by。buthavingdealtthusfarwithourlogicalmethods，Imustnowturntosomethingwhich，perhaps，youmayconsidermoreinteresting，or，atanyrate，moretangible。Butinrealitytherearebutfewthingsthatcanbemoreimportantforyoutounderstandthanthementalprocessesandthemeansbywhichweobtainscientificconclusionsandtheories。1Havinggrantedthattheinquiryisaproperone，andhavingdeterminedonthenatureofthemethodswearetopursueandwhichonlycanleadtosuccess，Imustnowturntotheconsiderationofourknowledgeofthenatureoftheprocesseswhichhaveresultedinthepresentconditionoforganicnature。

Here，letmesayatonce，lestsomeofyoumisunderstandme，thatIhaveextremelylittletoreport。Thequestionofhowthepresentconditionoforganicnaturecameabout，resolvesitselfintotwoquestions。Thefirstis：Howhasorganicorlivingmattercommenceditsexistence？Andthesecondis：Howhasitbeenperpetuated？OnthesecondquestionI

shallhavemoretosayhereafter。Butonthefirstone，whatInowhavetosaywillbeforthemostpartofanegativecharacter。

Ifyouconsiderwhatkindofevidencewecanhaveuponthismatter，itwillresolveitselfintotwokinds。Wemayhavehistoricalevidenceandwemayhaveexperimentalevidence。Itis，forexample，conceivable，thatinasmuchasthehardenedmudwhichformsaconsiderableportionofthethicknessoftheearth’scrustcontainsfaithfulrecordsofthepastformsoflife，andinasmuchasthesediffermoreandmoreaswegofurtherdown，——itispossibleandconceivablethatwemightcometosomeparticularbedorstratumwhichshouldcontaintheremainsofthosecreatureswithwhichorganiclifebeganupontheearth。Andifwedidso，andifsuchformsoforganiclifewerepreservable，weshouldhavewhatIwouldcallhistoricalevidenceofthemodeinwhichorganiclifebeganuponthisplanet。Manypersonswilltellyou，andindeedyouwillfinditstatedinmanyworksongeology，thatthishasbeendone，andthatwereallypossesssucharecord。therearesomewhoimaginethattheearliestformsoflifeofwhichwehaveasyetdiscoveredanyrecord，areintruththeformsinwhichanimallifebeganupontheglobe。Thegroundsonwhichtheybasethatsuppositionarethese：——Thatifyougothroughtheenormousthicknessoftheearth’scrustandgetdowntotheolderrocks，thehighervertebrateanimals——thequadrupeds，birds，andfishes——ceasetobefound。beneaththemyoufindonlytheinvertebrateanimals。andinthedeepestandlowestrocksthoseremainsbecomescantierandscantier，notinanyverygradualprogression，however，until，atlength，inwhataresupposedtobetheoldestrocks，theanimalremainswhicharefoundarealmostalwaysconfinedtofourforms——’Oldhamia’，whoseprecisenatureisnotknown，whetherplantoranimal。’Lingula’，akindofmollusc。’Trilobites’，acrustaceananimal，havingthesameessentialplanofconstruction，thoughdifferinginmanydetailsfromalobsterorcrab。andHymenocaris，whichisalsoacrustacean。Sothatyouhaveallthe’Fauna’reduced，atthisperiod，tofourforms：oneakindofanimalorplantthatweknownothingabout，andthreeundoubtedanimals——twocrustaceansandonemollusc。

Ithink，consideringtheorganizationofthesemolluscaandcrustacea，andlookingattheirverycomplexnature，thatitdoesindeedrequireaverystrongimaginationtoconceivethatthesewerethefirstcreatedofalllivingthings。Andyoumusttakeintoconsiderationthefactthatwehavenottheslightestproofthatthesewhichwecalltheoldestbedsarereallyso：Irepeat，wehavenottheslightestproofofit。Whenyoufindinsomeplacesthatinanenormousthicknessofrockstherearebutveryscantytracesoflife，orabsolutelynoneatall。andthatinotherpartsoftheworldrocksoftheverysameformationarecrowdedwiththerecordsoflivingforms，Ithinkitisimpossibletoplaceanyrelianceonthesupposition，ortofeeloneselfjustifiedinsupposingthatthesearetheformsinwhichlifefirstcommenced。IhavenottimeheretoenteruponthetechnicalgroundsuponwhichIamledtothisconclusion，——thatcouldhardlybedoneproperlyinhalfadozenlecturesonthatpartalone——ImustcontentmyselfwithsayingthatIdonotatallbelievethatthesearetheoldestformsoflife。

Iturntotheexperimentalsidetoseewhatevidencewehavethere。Toenableustosaythatweknowanythingabouttheexperimentaloriginationoforganizationandlife，theinvestigatoroughttobeabletotakeinorganicmatters，suchascarbonicacid，ammonia，water，andsalines，inanysortofinorganiccombination，andbeabletobuildthemupintoProteinmatter，andthatthatProteinmatteroughttobegintoliveinanorganicform。That，nobodyhasdoneasyet，andI

suspectitwillbealongwhilebeforeanybodydoesdoit。Butthethingisbynomeanssoimpossibleasitlooks。fortheresearchesofmodernchemistryhaveshownus——Iwon’tsaytheroadtowardsit，but，ifImaysosay，theyhaveshownthefinger-postpointingtotheroadthatmayleadtoit。

Itisnotmanyyearsago——andyoumustrecollectthatOrganicChemistryisayoungscience，notaboveacoupleofgenerationsold，——youmustnotexpecttoomuchofit。itisnotmanyyearsagosinceitwassaidtobeperfectlyimpossibletofabricateanyorganiccompound。thatistosay，anynon-mineralcompoundwhichistobefoundinanorganizedbeing。Itremainedsoforaverylongperiod。butitisnowaconsiderablenumberofyearssinceadistinguishedforeignchemistcontrivedtofabricateUrea，asubstanceofaverycomplexcharacter，whichformsoneofthewasteproductsofanimalstructures。Andoflateyearsanumberofothercompounds，suchasButyricAcid，andothers，havebeenaddedtothelist。IneednottellyouthatchemistryisanenormousdistancefromthegoalIindicate。allIwishtopointouttoyouis，thatitisbynomeanssafetosaythatthatgoalmaynotbereachedoneday。Itmaybethatitisimpossibleforustoproducetheconditionsrequisitetotheoriginationoflife。butwemustspeakmodestlyaboutthematter，andrecollectthatSciencehasputherfootuponthebottomroundoftheladder。Trulyhewouldbeaboldmanwhowouldventuretopredictwhereshewillbefiftyyearshence。

Thereisanotherinquirywhichbearsindirectlyuponthisquestion，anduponwhichImustsayafewwords。Youareallofyouawareofthephenomenaofwhatiscalledspontaneousgeneration。Ourforefathers，downtotheseventeenthcentury，orthereabouts，allimagined，inperfectlygoodfaith，thatcertainvegetableandanimalformsgavebirth，intheprocessoftheirdecomposition，toinsectlife。Thus，ifyouputapieceofmeatinthesun，andallowedittoputrefy，theyconceivedthatthegrubswhichsoonbegantoappearweretheresultoftheactionofapowerofspontaneousgenerationwhichthemeatcontained。Andtheycouldgiveyoureceiptsformakingvariousanimalandvegetablepreparationswhichwouldproduceparticularkindsofanimals。AverydistinguishedItaliannaturalist，namedRedi，tookupthequestion，atatimewheneverybodybelievedinit。amongothersourowngreatHarvey，thediscovererofthecirculationoftheblood。Youwillconstantlyfindhisnamequoted，however，asanopponentofthedoctrineofspontaneousgeneration。butthefactis，andyouwillseeitifyouwilltakethetroubletolookintohisworks，Harveybelieveditasprofoundlyasanymanofhistime。buthehappenedtoenunciateaverycuriousproposition——thateverylivingthingcamefroman’egg’。

hedidnotmeantousethewordinthesenseinwhichwenowemployit，heonlymeanttosaythateverylivingthingoriginatedinalittleroundedparticleoforganizedsubstance。anditisfromthiscircumstance，probably，thatthenotionofHarveyhavingopposedthedoctrineoriginated。ThencameRedi，andheproceededtoupsetthedoctrineinaverysimplemanner。Hemerelycoveredthepieceofmeatwithsomeveryfinegauze，andthenheexposedittothesameconditions。Theresultofthiswasthatnogrubsorinsectswereproduced。heprovedthatthegrubsoriginatedfromtheinsectswhocameanddepositedtheireggsinthemeat，andthattheywerehatchedbytheheatofthesun。Bythiskindofinquiryhethoroughlyupsetthedoctrineofspontaneousgeneration，forhistimeatleast。

Thencamethediscoveryandapplicationofthemicroscopetoscientificinquiries，whichshowedtonaturaliststhatbesidestheorganismswhichtheyalreadyknewaslivingbeingsandplants，therewereanimmensenumberofminutethingswhichcouldbeobtainedapparentlyalmostatwillfromdecayingvegetableandanimalforms。Thus，ifyoutooksomeordinaryblackpepperorsomehay，andsteepeditinwater，youwouldfindinthecourseofafewdaysthatthewaterhadbecomeimpregnatedwithanimmensenumberofanimalculesswimmingaboutinalldirections。Fromfactsofthiskindnaturalistswereledtorevivethetheoryofspontaneousgeneration。TheywereheadedherebyanEnglishnaturalist，——Needham，——andafterwardsinFrancebythelearnedBuffon。

Theysaidthatthesethingswereabsolutelybegotteninthewaterofthedecayingsubstancesoutofwhichtheinfusionwasmade。Itdidnotmatterwhetheryoutookanimalorvegetablematter，youhadonlytosteepitinwaterandexposeit，andyouwouldsoonhaveplentyofanimalcules。Theymadeanhypothesisaboutthiswhichwasaveryfairone。Theysaid，thismatteroftheanimalworld，orofthehigherplants，appearstobedead，butinrealityithasasortofdimlifeaboutit，which，ifitisplacedunderfairconditions，willcauseittobreakupintotheformsoftheselittleanimalcules，andtheywillgothroughtheirlivesinthesamewayastheanimalorplantofwhichtheyonceformedapart。

Thequestionnowbecameveryhotlydebated。Spallanzani，anItaliannaturalist，tookupoppositeviewstothoseofNeedhamandBuffon，andbymeansofcertainexperimentsheshowedthatitwasquitepossibletostoptheprocessbyboilingthewater，andclosingthevesselinwhichitwascontained。Oh！saidhisopponents。butwhatdoyouknowyoumaybedoingwhenyouheattheairoverthewaterinthisway？Youmaybedestroyingsomepropertyoftheairrequisiteforthespontaneousgenerationoftheanimalcules。

However，Spallanzani’sviewsweresupposedtobeupontherightside，andthoseoftheothersfellintodiscredit。althoughthefactwasthatSpallanzanihadnotmadegoodhisviews。Well，then，thesubjectcontinuedtoberevivedfromtimetotime，andexperimentsweremadebyseveralpersons。buttheseexperimentswerenotaltogethersatisfactory。

Itwasfoundthatifyouputaninfusioninwhichanimalculeswouldappearifitwereexposedtotheairintoavesselandboiledit，andthensealedupthemouthofthevessel，sothatnoair，savesuchashadbeenheatedto212degrees，couldreachitscontents，thatthennoanimalculeswouldbefound。butifyoutookthesamevesselandexposedtheinfusiontotheair，thenyouwouldgetanimalcules。Furthermore，itwasfoundthatifyouconnectedthemouthofthevesselwithared-hottubeinsuchawaythattheairwouldhavetopassthroughthetubebeforereachingtheinfusion，thatthenyouwouldgetnoanimalcules。Yetanotherthingwasnoticed：ifyoutooktwoflaskscontainingthesamekindofinfusion，andleftoneentirelyexposedtotheair，andinthemouthoftheotherplacedaballofcottonwool，sothattheairwouldhavetofilteritselfthroughitbeforereachingtheinfusion，thatthen，althoughyoumighthaveplentyofanimalculesinthefirstflask，youwouldcertainlyobtainnonefromthesecond。

Theseexperiments，yousee，alltendedtowardsoneconclusion——thattheinfusoriaweredevelopedfromlittleminutesporesoreggswhichwereconstantlyfloatingintheatmosphere，whichlosetheirpowerofgerminationifsubjectedtoheat。Butoneobservernowmadeanotherexperimentwhichseemedtogoentirelytheotherway，andpuzzledhimaltogether。HetooksomeofthisboiledinfusionthatIhavebeenspeakingof，andbytheuseofamercurialbath——akindoftroughusedinlaboratories——hedeftlyinvertedavesselcontainingtheinfusionintothemercury，sothatthelatterreachedalittlebeyondthelevelofthemouthofthe’inverted’vessel。Youseethathethushadaquantityoftheinfusionshutofffromanypossiblecommunicationwiththeouterairbybeinginverteduponabedofmercury。

Hethenpreparedsomepureoxygenandnitrogengases，andpassedthembymeansofatubegoingfromtheoutsideofthevessel，upthroughthemercuryintotheinfusion。sothathethushaditexposedtoaperfectlypureatmosphereofthesameconstituentsastheexternalair。

Ofcourse，heexpectedhewouldgetnoinfusorialanimalculesatallinthatinfusion。but，tohisgreatdismayanddiscomfiture，hefoundhealmostalwaysdidgetthem。

Furthermore，ithasbeenfoundthatexperimentsmadeinthemannerdescribedaboveanswerwellwithmostinfusions。butthatifyoufillthevesselwithboiledmilk，andthenstoptheneckwithcotton-wool，you’will’haveinfusoria。Sothatyouseethereweretwoexperimentsthatbroughtyoutoonekindofconclusion，andthreetoanother。whichwasamostunsatisfactorystateofthingstoarriveatinascientificinquiry。

Somefewyearsafterthis，thequestionbegantobeveryhotlydiscussedinFrance。TherewasM。Pouchet，aprofessoratRouen，averylearnedman，butcertainlynotaveryrigidexperimentalist。Hepublishedanumberofexperimentsofhisown，someofwhichwereveryingenious，toshowthatifyouwenttoworkinaproperway，therewasatruthinthedoctrineofspontaneousgeneration。Well，itwasoneofthemostfortunatethingsintheworldthatM。Pouchettookupthisquestion，becauseitinducedadistinguishedFrenchchemist，M。Pasteur，totakeupthequestionontheotherside。andhehascertainlyworkeditoutinthemostperfectmanner。Iamgladtosay，too，thathehaspublishedhisresearchesintimetoenablemetogiveyouanaccountofthem。HeverifiedalltheexperimentswhichIhavejustmentionedtoyou——andthenfindingthoseextraordinaryanomalies，asinthecaseofthemercurybathandthemilk，hesethimselftoworktodiscovertheirnature。Inthecaseofmilkhefoundittobeaquestionoftemperature。Milkinafreshstateisslightlyalkaline。anditisaverycuriouscircumstance，butthisveryslightdegreeofalkalinityseemstohavetheeffectofpreservingtheorganismswhichfallintoitfromtheairfrombeingdestroyedatatemperatureof212degrees，whichistheboilingpoint。Butifyouraisethetemperature10degreeswhenyouboilit，themilkbehaveslikeeverythingelse。andiftheairwithwhichitcomesincontact，afterbeingboiledatthistemperature，ispassedthroughared-hottube，youwillnotgetatraceoforganisms。

Hethenturnedhisattentiontothemercurybath，andfoundonexaminationthatthesurfaceofthemercurywasalmostalwayscoveredwithaveryfinedust。Hefoundthateventhemercuryitselfwaspositivelyfulloforganicmatters。thatfrombeingconstantlyexposedtotheair，ithadcollectedanimmensenumberoftheseinfusorialorganismsfromtheair。Well，underthesecircumstanceshefeltthatthecasewasquiteclear，andthatthemercurywasnotwhatithadappearedtoM。Schwanntobe，——abartotheadmissionoftheseorganisms。butthat，inreality，itactedasareservoirfromwhichtheinfusionwasimmediatelysuppliedwiththelargequantitythathadsopuzzledhim。

Butnotcontentwithexplainingtheexperimentsofothers，M。Pasteurwenttoworktosatisfyhimselfcompletely。Hesaidtohimself：Ifmyviewisright，andif，inpointoffact，alltheseappearancesofspontaneousgenerationarealtogetherduetothefallingofminutegermssuspendedintheatmosphere，——why，Ioughtnotonlytobeabletoshowthegerms，butIoughttobeabletocatchandsowthem，andproducetheresultingorganisms。He，accordingly，constructedaveryingeniousapparatustoenablehimtoaccomplishthistrappingofthisgermdustintheair。Hefixedinthewindowofhisroomaglasstube，inthecentreofwhichhehadplacedaballofgun-cotton，which，asyouallknow，isordinarycotton-wool，which，fromhavingbeensteepedinstrongacid，isconvertedintoasubstanceofgreatexplosivepower。Itisalsosolubleinalcoholandether。Oneendoftheglasstubewas，ofcourse，opentotheexternalair。andattheotherendofitheplacedanaspirator，acontrivanceforcausingacurrentoftheexternalairtopassthroughthetube。Hekeptthisapparatusgoingforfour-and-twentyhours，andthenremovedthe’dusted’gun-cotton，anddissolveditinalcoholandether。Hethenallowedthistostandforafewhours，andtheresultwas，thataveryfinedustwasgraduallydepositedatthebottomofit。Thatdust，onbeingtransferredtothestageofamicroscope，wasfoundtocontainanenormousnumberofstarchgrains。Youknowthatthematerialsofourfoodandthegreaterportionofplantsarecomposedofstarch，andweareconstantlymakinguseofitinavarietyofways，sothatthereisalwaysaquantityofitsuspendedintheair。Itisthesestarchgrainswhichformmanyofthosebrightspecksthatweseedancinginarayoflightsometimes。Butbesidesthese，M。Pasteurfoundalsoanimmensenumberofotherorganicsubstancessuchassporesoffungi，whichhadbeenfloatingaboutintheairandhadgotcagedinthisway。

Hewentfarther，andsaidtohimself，Ifthesereallyarethethingsthatgiverisetotheappearanceofspontaneousgeneration，Ioughttobeabletotakeaballofthis’dusted’gun-cottonandputitintooneofmyvessels，containingthatboiledinfusionwhichhasbeenkeptawayfromtheair，andinwhichnoinfusoriaareatpresentdeveloped，andthen，ifIamright，theintroductionofthisgun-cottonwillgiverisetoorganisms。

Accordingly，hetookoneofthesevesselsofinfusion，whichhadbeenkepteighteenmonths，withouttheleastappearanceoflife，andbyamostingeniouscontrivance，hemanagedtobreakitopenandintroducesuchaballofgun-cotton，withoutallowingtheinfusionorthecottonballtocomeintocontactwithanyairbutthatwhichhadbeensubjectedtoaredheat，andintwenty-fourhourshehadthesatisfactionoffindingalltheindicationsofwhathadbeenhithertocalledspontaneousgeneration。Hehadsucceededincatchingthegermsanddevelopingorganismsinthewayhehadanticipated。

Itnowstruckhimthatthetruthofhisconclusionsmightbedemonstratedwithoutalltheapparatushehademployed。Todothis，hetooksomedecayinganimalorvegetablesubstance，suchasurine，whichisanextremelydecomposablesubstance，orthejuiceofyeast，orperhapssomeotherartificialpreparation，andfilledavesselhavingalongtubularneckwithit。HethenboiledtheliquidandbentthatlongneckintoanSshapeorzig-zag，leavingitopenattheend。Theinfusionthengavenotraceofanyappearanceofspontaneousgeneration，howeverlongitmightbeleft，asallthegermsintheairweredepositedinthebeginningofthebentneck。Hethencutthetubeclosetothevessel，andallowedtheordinaryairtohavefreeanddirectaccess。andtheresultofthatwastheappearanceoforganismsinit，assoonastheinfusionhadbeenallowedtostandlongenoughtoallowofthegrowthofthoseitreceivedfromtheair，whichwasaboutforty-eighthours。TheresultofM。Pasteur’sexperimentsproved，therefore，inthemostconclusivemanner，thatalltheappearancesofspontaneousgenerationarosefromnothingmorethanthedepositionofthegermsoforganismswhichwereconstantlyfloatingintheair。

Tothisconclusion，however，theobjectionwasmade，thatifthatwerethecause，thentheairwouldcontainsuchanenormousnumberofthesegerms，thatitwouldbeacontinualfog。ButM。Pasteurrepliedthattheyarenotthereinanythinglikethenumberwemightsuppose，andthatanexaggeratedviewhasbeenheldonthatsubject。heshowedthatthechancesofanimalorvegetablelifeappearingininfusions，dependentirelyontheconditionsunderwhichtheyareexposed。Iftheyareexposedtotheordinaryatmospherearoundus，why，ofcourse，youmayhaveorganismsappearingearly。But，ontheotherhand，iftheyareexposedtoairfromagreatheight，orfromsomeveryquietcellar，youwilloftennotfindasingletraceoflife。

SothatM。Pasteurarrivedatlastattheclearanddefiniteresult，thatalltheseappearancesarelikethecaseofthewormsinthepieceofmeat，whichwasrefutedbyRedi，simplygermscarriedbytheairanddepositedintheliquidsinwhichtheyafterwardsappear。Formyownpart，Iconceivethat，withtheparticularsofM。Pasteur’sexperimentsbeforeus，wecannotfailtoarriveathisconclusions。andthatthedoctrineofspontaneousgenerationhasreceivedafinal’coupdegrace’。

You，ofcourse，understandthatallthisinnowayinterfereswiththe’possibility’ofthefabricationoforganicmattersbythedirectmethodtowhichIhavereferred，remoteasthatpossibilitymaybe。

[Footnote]1ThosewhowishtostudyfullythedoctrinesofwhichIhaveendeavouredtogivesomeroughandreadyillustrations，mustreadMr。JohnStuartMill’s’SystemofLogic’。

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THEPERPETUATIONOFLIVINGBEINGS，HEREDITARYTRANSMISSIONAND

VARIATION

Theinquirywhichweundertook，atourlastmeeting，intothestateofourknowledgeofthecausesofthephenomenaoforganicnature，——ofthepastandofthepresent，——resolveditselfintotwosubsidiaryinquiries：thefirstwas，whetherweknowanything，eitherhistoricallyorexperimentally，ofthemodeoforiginoflivingbeings。thesecondsubsidiaryinquirywas，whether，grantingtheorigin，weknowanythingabouttheperpetuationandmodificationsoftheformsoforganicbeings。ThereplywhichIhadtogivetothefirstquestionwasaltogethernegative，andthechiefresultofmylastlecturewas，that，neitherhistoricallynorexperimentally，doweatpresentknowanythingwhatsoeverabouttheoriginoflivingforms。Wesawthat，historically，wearenotlikelytoknowanythingaboutit，althoughwemayperhapslearnsomethingexperimentally。butthatatpresentweareanenormousdistancefromthegoalIindicated。

Inow，then，takeupthenextquestion，Whatdoweknowofthereproduction，theperpetuation，andthemodificationsoftheformsoflivingbeings，supposingthatwehaveputthequestionastotheiroriginationononeside，andhaveassumedthatatpresentthecausesoftheiroriginationarebeyondus，andthatweknownothingaboutthem？

Uponthisquestionthestateofourknowledgeisextremelydifferent。

itisexceedinglylarge，and，ifnotcomplete，ourexperienceiscertainlymostextensive。Itwouldbeimpossibletolayitallbeforeyou，andthemostIcando，orneeddoto-night，istotakeuptheprincipalpointsandputthembeforeyouwithsuchprominenceasmaysubservethepurposesofourpresentargument。

Themethodoftheperpetuationoforganicbeingsisoftwokinds，——theasexualandthesexual。Inthefirsttheperpetuationtakesplacefromandbyaparticularactofanindividualorganism，whichsometimesmaynotbeclassedasbelongingtoanysexatall。Inthesecondcase，itisinconsequenceofthemutualactionandinteractionofcertainportionsoftheorganismsofusuallytwodistinctindividuals，——themaleandthefemale。Thecasesofasexualperpetuationarebynomeanssocommonasthecasesofsexualperpetuation。andtheyarebynomeanssocommonintheanimalasinthevegetableworld。Youareallprobablyfamiliarwiththefact，asamatterofexperience，thatyoucanpropagateplantsbymeansofwhatarecalledcuttings。forexample，thatbytakingacuttingfromageraniumplant，andrearingitproperly，bysupplyingitwithlightandwarmthandnourishmentfromtheearth，itgrowsupandtakestheformofitsparent，havingallthepropertiesandpeculiaritiesoftheoriginalplant。

Sometimesthisprocess，whichthegardenerperformsartificially，takesplacenaturally。thatistosay，alittlebulb，orportionoftheplant，detachesitself，dropsoff，andbecomescapableofgrowingasaseparatething。Thatisthecasewithmanybulbousplants，whichthrowoffinthiswaysecondarybulbs，whicharelodgedinthegroundandbecomedevelopedintoplants。Thisisanasexualprocess，andfromitresultstherepetitionorreproductionoftheformoftheoriginalbeingfromwhichthebulbproceeds。

Amonganimalsthesamethingtakesplace。Amongthelowerformsofanimallife，theinfusorialanimalculaewehavealreadyspokenofthrowoffcertainportions，orbreakthemselvesupinvariousdirections，sometimestransverselyorsometimeslongitudinally。ortheymaygiveoffbuds，whichdetachthemselvesanddevelopintotheirproperforms。

Thereisthecommonfresh-waterPolype，forinstance，whichmultipliesitselfinthisway。Justinthesamewayasthegardenerisabletomultiplyandreproducethepeculiaritiesandcharactersofparticularplantsbymeansofcuttings，socanthephysiologicalexperimentalist——aswasshownbytheAbbeTrembleymanyyearsago——socanhedothesamethingwithmanyofthelowerformsofanimallife。

M。deTrembleyshowedthatyoucouldtakeapolypeandcutitintotwo，orfour，ormanypieces，mutilatingitinalldirections，andthepieceswouldstillgrowupandreproducecompletelytheoriginalformoftheanimal。Theseareallcasesofasexualmultiplication，andthereareotherinstances，andstillmoreextraordinaryones，inwhichthisprocesstakesplacenaturally，inamorehidden，amorereconditekindofway。Youareallofyoufamiliarwiththoselittlegreeninsects，the’Aphis’orblight，asitiscalled。Theselittleanimals，duringaveryconsiderablepartoftheirexistence，multiplythemselvesbymeansofakindofinternalbudding，thebudsbeingdevelopedintoessentiallyasexualanimals，whichareneithermalenorfemale。theybecomeconvertedintoyoung’Aphides’，whichrepeattheprocess，andtheiroffspringafterthem，andsoonagain。youmaygoonfornineorten，oreventwentyormoresuccessions。andthereisnoverygoodreasontosayhowsoonitmightterminate，orhowlongitmightnotgooniftheproperconditionsofwarmthandnourishmentwerekeptup。

Sexualreproductionisquiteadistinctmatter。Here，inallthesecases，whatisrequiredisthedetachmentoftwoportionsoftheparentalorganisms，whichportionsweknowastheeggandthespermatozoon。Inplantsitistheovuleandthepollen-grain，asinthefloweringplants，ortheovuleandtheantherozooid，asintheflowerless。Amongallformsofanimallife，thespermatozoaproceedfromthemalesex，andtheeggistheproductofthefemale。Now，whatisremarkableaboutthismodeofreproductionisthis，thattheeggbyitself，orthespermatozoabythemselves，areunabletoassumetheparentalform。butiftheybebroughtintocontactwithoneanother，theeffectofthemixtureoforganicsubstancesproceedingfromtwosourcesappearstoconferanaltogethernewvigourtothemixedproduct。

Thisprocessisbroughtabout，asweallknow，bythesexualintercourseofthetwosexes，andiscalledtheactofimpregnation。

Theresultofthisactonthepartofthemaleandfemaleis，thattheformationofanewbeingissetupintheovuleoregg。thisovuleoreggsoonbeginstobedividedandsubdivided，andtobefashionedintovariouscomplexorganisms，andeventuallytodevelopintotheformofoneofitsparents，asIexplainedinthefirstlecture。Thesearetheprocessesbywhichtheperpetuationoforganicbeingsissecured。Whythereshouldbethetwomodes——whythisre-invigorationshouldberequiredonthepartofthefemaleelementwedonotknow。butitismostassuredlythefact，anditispresumable，that，howeverlongtheprocessofasexualmultiplicationcouldbecontinued，Isaythereisgoodreasontobelievethatitwouldcometoanendifanewcommencementwerenotobtainedbyaconjunctionofthetwosexualelements。

Thatcharacterwhichiscommontothesetwodistinctprocessesisthis，that，whetherweconsiderthereproduction，orperpetuation，ormodificationoforganicbeingsastheytakeplaceasexually，orastheymaytakeplacesexually，——ineithercase，Isay，theoffspringhasaconstanttendencytoassume，speakinggenerally，thecharacteroftheparent。AsIsaidjustnow，ifyoutakeaslipofaplant，andtenditwithcare，itwilleventuallygrowupanddevelopintoaplantlikethatfromwhichithadsprung。andthistendencyissostrongthat，asgardenersknow，thismodeofmultiplyingbymeansofcuttingsistheonlysecuremodeofpropagatingverymanyvarietiesofplants。thepeculiarityoftheprimitivestockseemstobebetterpreservedifyoupropagateitbymeansofaslipthanifyouresorttothesexualmode。

Again，inexperimentsupontheloweranimals，suchasthepolype，towhichIhavereferred，itismostextraordinarythat，althoughcutupintovariouspieces，eachparticularpiecewillgrowupintotheformoftheprimitivestock。thehead，ifseparated，willreproducethebodyandthetail。andifyoucutoffthetail，youwillfindthatthatwillreproducethebodyandalltherestofthemembers，withoutinanywaydeviatingfromtheplanoftheorganismfromwhichtheseportionshavebeendetached。Andsofardoesthisgo，thatsomeexperimentalistshavecarefullyexaminedthelowerordersofanimals，——amongthemtheAbbeSpallanzani，whomadeanumberofexperimentsuponsnailsandsalamanders，——andhavefoundthattheymightmutilatethemtoanincredibleextent。thatyoumightcutoffthejaworthegreaterpartofthehead，orthelegorthetail，andrepeattheexperimentseveraltimes，perhaps，cuttingoffthesamememberagainandagain。andyeteachofthosetypeswouldbereproducedaccordingtotheprimitivetype：naturemakingnomistake，neverputtingonafreshkindofleg，orhead，ortail，butalwaystendingtorepeatandtoreturntotheprimitivetype。

Itisthesameinsexualreproduction：itisamatterofperfectlycommonexperience，thatthetendencyonthepartoftheoffspringalwaysis，speakingbroadly，toreproducetheformoftheparents。Theproverbhasitthatthethistledoesnotbringforthgrapes。so，amongourselves，thereisalwaysalikeness，moreorlessmarkedanddistinct，betweenchildrenandtheirparents。Thatisamatteroffamiliarandordinaryobservation。Wenoticethesamethingoccurringinthecasesofthedomesticanimals——dogs，forinstance，andtheiroffspring。Inallthesecasesofpropagationandperpetuation，thereseemstobeatendencyintheoffspringtotakethecharactersoftheparentalorganisms。Tothattendencyaspecialnameisgiven——itiscalled’Atavism’，itexpressesthistendencytoreverttotheancestraltype，andcomesfromtheLatinword’atavus’，ancestor。

Well，this’Atavism’whichIshallspeakof，is，asIsaidbefore，oneofthemostmarkedandstrikingtendenciesoforganicbeings。but，sidebysidewiththishereditarytendencythereisanequallydistinctandremarkabletendencytovariation。Thetendencytoreproducetheoriginalstockhas，asitwere，itslimits，andsidebysidewithitthereisatendencytovaryincertaindirections，asifthereweretwoopposingpowersworkingupontheorganicbeing，onetendingtotakeitinastraightline，andtheothertendingtomakeitdivergefromthatstraightline，firsttoonesideandthentotheother。

Sothatyouseethesetwotendenciesneednotpreciselycontradictoneanother，astheultimateresultmaynotalwaysbeveryremotefromwhatwouldhavebeenthecaseifthelinehadbeenquitestraight。

Thistendencytovariationislessmarkedinthatmodeofpropagationwhichtakesplaceasexually。itisinthatmodethattheminorcharactersofanimalandvegetablestructuresaremostcompletelypreserved。Still，itwillhappensometimes，thatthegardener，whenhehasplantedacuttingofsomefavouriteplant，willfind，contrarytohisexpectation，thattheslipgrowsupalittledifferentfromtheprimitivestock——thatitproducesflowersofadifferentcolourormake，orsomedeviationinonewayoranother。Thisiswhatiscalledthe’sporting’ofplants。

Inanimalsthephenomenaofasexualpropagationaresoobscure，thatatpresentwecannotbesaidtoknowmuchaboutthem。butifweturntothatmodeofperpetuationwhichresultsfromthesexualprocess，thenwefindvariationaperfectlyconstantoccurrence，toacertainextent。

and，indeed，Ithinkthatacertainamountofvariationfromtheprimitivestockisthenecessaryresultofthemethodofsexualpropagationitself。for，inasmuchasthethingpropagatedproceedsfromtwoorganismsofdifferentsexesanddifferentmakesandtemperaments，andastheoffspringistobeeitherofonesexortheother，itisquiteclearthatitcannotbeanexactdiagonalofthetwo，oritwouldbeofnosexatall。itcannotbeanexactintermediateformbetweenthatofeachofitsparents——itmustdeviatetoonesideortheother。

Youdonotfindthatthemalefollowstheprecisetypeofthemaleparent，nordoesthefemalealwaysinherittheprecisecharacteristicsofthemother，——thereisalwaysaproportionofthefemalecharacterinthemaleoffspring，andofthemalecharacterinthefemaleoffspring。

Thatmustbequiteplaintoallofyouwhohavelookedatallattentivelyonyourownchildrenorthoseofyourneighbours。youwillhavenoticedhowveryoftenitmayhappenthatthesonshallexhibitthematernaltypeofcharacter，orthedaughterpossessthecharacteristicsofthefather’sfamily。Thereareallsortsofintermixturesandintermediateconditionsbetweenthetwo，wherecomplexion，orbeauty，orfiftyotherdifferentpeculiaritiesbelongingtoeithersideofthehouse，arereproducedinothermembersofthesamefamily。Indeed，itissometimestoberemarkedinthiskindofvariation，thatthevarietybelongs，strictlyspeaking，toneitheroftheimmediateparents。youwillseeachildinafamilywhoisnotlikeeitheritsfatheroritsmother。butsomeoldpersonwhoknewitsgrandfatherorgrandmother，or，itmaybe，anuncle，or，perhaps，evenamoredistantrelative，willseeagreatsimilaritybetweenthechildandoneofthese。Inthiswayitconstantlyhappensthatthecharacteristicofsomepreviousmemberofthefamilycomesoutandisreproducedandrecognisedinthemostunexpectedmanner。

Butapartfromthatmatterofgeneralexperience，therearesomecaseswhichputthatcuriousmixtureinaveryclearlight。YouareawarethattheoffspringoftheAssandtheHorse，orratherofthehe-AssandtheMare，iswhatiscalledaMule。and，ontheotherhand，theoffspringoftheStallionandtheshe-Assiswhatiscalleda’Hinny’。

Ineversawonemyself。buttheyhavebeenverycarefullystudied。Now，thecuriousthingisthis，thatalthoughyouhavethesameelementsintheexperimentineachcase，theoffspringisentirelydifferentincharacter，accordingasthemaleinfluencecomesfromtheAssortheHorse。WheretheAssisthemale，asinthecaseoftheMule，youfindthattheheadislikethatoftheAss，thattheearsarelong，thetailistuftedattheend，thefeetaresmall，andthevoiceisanunmistakablebray。theseareallpointsofsimilaritytotheAss。but，ontheotherhand，thebarrelofthebodyandthecutoftheneckaremuchmorelikethoseoftheMare。Then，ifyoulookattheHinny，——theresultoftheunionoftheStallionandtheshe-Ass，thenyoufinditistheHorsethathasthepredominance。thattheheadismorelikethatoftheHorse，theearsareshorter，thelegscoarser，andthetypeisaltogetheraltered。whilethevoice，insteadofbeingabray，istheordinaryneighoftheHorse。Here，yousee，isamostcuriousthing：

youtakeexactlythesameelements，AssandHorse，butyoucombinethesexesinadifferentmanner，andtheresultismodifiedaccordingly。

Youhaveinthiscase，however，aresultwhichisnotgeneralanduniversal——thereisusuallyanimportantpreponderance，butnotalwaysonthesameside。

Here，then，isoneintelligible，and，perhaps，necessarycauseofvariation：thefact，thattherearetwosexessharingintheproductionoftheoffspring，andthatthesharetakenbyeachisdifferentandvariable，notonlyforeachcombination，butalsofordifferentmembersofthesamefamily。

Secondly，thereisavariation，toacertainextent——though，inallprobability，theinfluenceofthiscausehasbeenverymuchexaggerated——butthereisnodoubtthatvariationisproduced，toacertainextent，bywhatarecommonlyknownasexternalconditions，——suchastemperature，food，warmth，andmoisture。Inthelongrun，everyvariationdepends，insomesense，uponexternalconditions，seeingthateverythinghasacauseofitsown。Iusethetermexternalconditionsnowinthesenseinwhichitisordinarilyemployed：certainitis，thatexternalconditionshaveadefiniteeffect。Youmaytakeaplantwhichhassingleflowers，andbydealingwiththesoil，andnourishment，andsoon，youmayby-and-byconvertsingleflowersintodoubleflowers，andmakethornsshootoutintobranches。Youmaythickenormakevariousmodificationsintheshapeofthefruit。Inanimals，too，youmayproduceanalogouschangesinthisway，asinthecaseofthatdeepbronzecolourwhichpersonsrarelyloseafterhavingpassedanylengthoftimeintropicalcountries。Youmayalsoalterthedevelopmentofthemusclesverymuch，bydintoftraining。alltheworldknowsthatexercisehasagreateffectinthisway。wealwaysexpecttofindthearmofablacksmithhardandwiry，andpossessingalargedevelopmentofthebrachialmuscles。Nodoubttraining，whichisoneoftheformsofexternalconditions，convertswhatareoriginallyonlyinstructions，teachings，intohabits，or，inotherwords，intoorganizations，toagreatextent。butthissecondcauseofvariationcannotbeconsideredtobebyanymeansalargeone。ThethirdcausethatIhavetomention，however，isaveryextensiveone。Itisonethat，forwantofabettername，hasbeencalledspontaneousvariation。whichmeansthatwhenwedonotknowanythingaboutthecauseofphenomena，wecallitspontaneous。Intheorderlychainofcausesandeffectsinthisworld，thereareveryfewthingsofwhichitcanbesaidwithtruththattheyarespontaneous。Certainlynotinthesephysicalmatters，——inthesethereisnothingofthekind，——everythingdependsonpreviousconditions。Butwhenwecannottracethecauseofphenomena，wecallthemspontaneous。

Ofthesevariations，multitudinousastheyare，butlittleisknownwithperfectaccuracy。Iwillmentiontoyousometwoorthreecases，becausetheyareveryremarkableinthemselves，andalsobecauseI

shallwanttousethemafterwards。Reaumur，afamousFrenchnaturalist，agreatmanyyearsago，inanessaywhichhewroteupontheartofhatchingchickens，——whichwasindeedaverycuriousessay，——hadoccasiontospeakofvariationsandmonstrosities。Oneveryremarkablecasehadcomeunderhisnoticeofavariationintheformofahumanmember，inthepersonofaMaltese，ofthenameofGratioKelleia，whowasbornwithsixfingersuponeachhand，andthelikenumberoftoestoeachofhisfeet。Thatwasacaseofspontaneousvariation。Nobodyknowswhyhewasbornwiththatnumberoffingersandtoes，andaswedon’tknow，wecallitacaseofspontaneousvariation。Thereisanotherremarkablecasealso。Iselectthese，becausetheyhappentohavebeenobservedandnotedverycarefullyatthetime。Itfrequentlyhappensthatavariationoccurs，butthepersonswhonoticeitdonottakeanycareinnotingdowntheparticulars，untilatlength，wheninquiriescometobemade，theexactcircumstancesareforgotten。andhence，multitudinousasmaybesuchspontaneousvariations，itisexceedinglydifficulttogetattheoriginofthem。

ThesecondcaseisoneofwhichyoumayfindthewholedetailsinthePhilosophicalTransactionsfortheyear1813，inapapercommunicatedbyColonelHumphreytothePresidentoftheRoyalSociety，——OnanewVarietyintheBreedofSheep，givinganaccountofaveryremarkablebreedofsheep，whichatonetimewaswellknowninthenorthernstatesofAmerica，andwhichwentbythenameoftheAnconortheOtterbreedofsheep。Intheyear1791，therewasafarmerofthenameofSethWrightinMassachusetts，whohadaflockofsheep，consistingofaramand，Ithink，ofsometwelveorthirteenewes。Ofthisflockofewes，oneatthebreeding-timeborealambwhichwasverysingularlyformed。

ithadaverylongbody，veryshortlegs，andthoselegswerebowed！I

willtellyouby-and-byhowthissingularvariationinthebreedofsheepcametobenoted，andtohavetheprominencethatitnowhas。Forthepresent，Imentiononlythesetwocases。buttheextentofvariationinthebreedofanimalsisperfectlyobvioustoanyonewhohasstudiednaturalhistorywithordinaryattention，ortoanypersonwhocomparesanimalswithothersofthesamekind。Itisstrictlytruethatthereareneveranytwospecimenswhichareexactlyalike。howeversimilar，theywillalwaysdifferinsomecertainparticular。

NowletusgobacktoAtavism，——tothehereditarytendencyIspokeof。

Whatwillcomeofavariationwhenyoubreedfromit，whenAtavismcomes，ifImaysayso，tointersectvariation？ThetwocasesofwhichIhavementionedthehistory，giveamostexcellentillustrationofwhatoccurs。GratioKelleia，theMaltese，marriedwhenhewastwenty-twoyearsofage，and，asIsupposetherewerenosix-fingeredladiesinMalta，hemarriedanordinaryfive-fingeredperson。Theresultofthatmarriagewasfourchildren。thefirst，whowaschristenedSalvator，hadsixfingersandsixtoes，likehisfather。thesecondwasGeorge，whohadfivefingersandtoes，butoneofthemwasdeformed，showingatendencytovariation。thethirdwasAndre。hehadfivefingersandfivetoes，quiteperfect。thefourthwasagirl，Marie。shehadfivefingersandfivetoes，butherthumbsweredeformed，showingatendencytowardthesixth。

Thesechildrengrewup，andwhentheycametoadultyears，theyallmarried，andofcourseithappenedthattheyallmarriedfive-fingeredandfive-toedpersons。Nowletusseewhatweretheresults。Salvatorhadfourchildren。theyweretwoboys，agirl，andanotherboy。thefirsttwoboysandthegirlweresix-fingeredandsix-toedliketheirgrandfather。thefourthboyhadonlyfivefingersandfivetoes。Georgehadonlyfourchildren。thereweretwogirlswithsixfingersandsixtoes。therewasonegirlwithsixfingersandfivetoesontherightside，andfivefingersandfivetoesontheleftside，sothatshewashalfandhalf。Thelast，aboy，hadfivefingersandfivetoes。Thethird，Andre，youwillrecollect，wasperfectlywell-formed，andhehadmanychildrenwhosehandsandfeetwereallregularlydeveloped。Marie，thelast，who，ofcourse，marriedamanwhohadonlyfivefingers，hadfourchildren。thefirst，aboy，wasbornwithsixtoes，buttheotherthreewerenormal。

Nowobservewhatveryextraordinaryphenomenaarepresentedhere。Youhaveanaccidentalvariationarisingfromwhatyoumaycallamonstrosity。youhavethatmonstrositytendencyorvariationdilutedinthefirstinstancebyanadmixturewithafemaleofnormalconstruction，andyouwouldnaturallyexpectthat，intheresultsofsuchanunion，themonstrosity，ifrepeated，wouldbeinequalproportionwiththenormaltype。thatistosay，thatthechildrenwouldbehalfandhalf，sometakingthepeculiarityofthefather，andtheothersbeingofthepurelynormaltypeofthemother。butyouseewehaveagreatpreponderanceoftheabnormaltype。Well，thiscomestobemixedoncemorewiththepure，thenormaltype，andtheabnormalisagainproducedinlargeproportion，notwithstandingtheseconddilution。Nowwhatwouldhavehappenediftheseabnormaltypeshadintermarriedwitheachother。thatistosay，supposethetwoboysofSalvatorhadtakenitintotheirheadstomarrytheirfirstcousins，thetwofirstgirlsofGeorge，theiruncle？Youwillrememberthatthesearealloftheabnormaltypeoftheirgrandfather。Theresultwouldprobablyhavebeen，thattheiroffspringwouldhavebeenineverycaseafurtherdevelopmentofthatabnormaltype。Youseeitisonlyinthefourth，inthepersonofMarie，thatthetendency，whenitappearsbutslightlyinthesecondgeneration，iswashedoutinthethird，whiletheprogenyofAndre，whoescapedinthefirstinstance，escapealtogether。

Wehaveinthiscaseagoodexampleofnature’stendencytotheperpetuationofavariation。Hereitiscertainlyavariationwhichcarriedwithitnouseorbenefit。andyetyouseethetendencytoperpetuationmaybesostrong，that，notwithstandingagreatadmixtureofpureblood，thevarietycontinuesitselfuptothethirdgeneration，whichislargelymarkedwithit。Inthiscase，asIhavesaid，therewasnomeansofthesecondgenerationintermarryingwithanybutfive-fingeredpersons，andthequestionnaturallysuggestsitself，Whatwouldhavebeentheresultofsuchmarriage？Reaumurnarratesthiscaseonlyasfarasthethirdgeneration。Certainlyitwouldhavebeenanexceedinglycuriousthingifwecouldhavetracedthismatteranyfurther。hadthecousinsintermarried，asix-fingeredvarietyofthehumanracemighthavebeensetup。

Toshowyouthatthissuppositionisbynomeansanunreasonableone，letmenowpointoutwhattookplaceinthecaseofSethWright’ssheep，whereithappenedtobeamatterofmomenttohimtoobtainabreedorraiseaflockofsheeplikethataccidentalvarietythatI

havedescribed——andIwilltellyouwhy。InthatpartofMassachusettswhereSethWrightwasliving，thefieldswereseparatedbyfences，andthesheep，whichwereveryactiveandrobust，wouldroamabroad，andwithoutmuchdifficultyjumpoverthesefencesintootherpeople’sfarms。Asamatterofcourse，thisexuberantactivityonthepartofthesheepconstantlygaverisetoallsortsofquarrels，bickerings，andcontentionsamongthefarmersoftheneighbourhood。soitoccurredtoSethWright，whowas，likehissuccessors，moreorless’cute，thatifhecouldgetastockofsheeplikethosewiththebandylegs，theywouldnotbeabletojumpoverthefencessoreadily，andheacteduponthatidea。Hekilledhisoldram，andassoonastheyoungonearrivedatmaturity，hebredaltogetherfromit。TheresultwasevenmorestrikingthaninthehumanexperimentwhichImentionedjustnow。

ColonelHumphreystestifiesthatitalwayshappenedthattheoffspringwereeitherpureAnconsorpureordinarysheep。thatinnocasewasthereanymixingoftheAnconswiththeothers。Inconsequenceofthis，inthecourseofaveryfewyears，thefarmerwasabletogetaveryconsiderableflockofthisvariety，andalargenumberofthemwerespreadthroughoutMassachusetts。Mostunfortunately，however——I

supposeitwasbecausetheyweresocommon——nobodytookenoughnoticeofthemtopreservetheirskeletons。andalthoughColonelHumphreysstatesthathesentaskeletontothePresidentoftheRoyalSocietyatthesametimethatheforwardedhispaper，Iamafraidthatthevarietyhasentirelydisappeared。forashorttimeafterthesesheephadbecomeprevalentinthatdistrict，theMerinosheepwereintroduced。andastheirwoolwasmuchmorevaluable，andastheywereaquietraceofsheep，andshowednotendencytotrespassorjumpoverfences，theOtterbreedofsheep，thewoolofwhichwasinferiortothatoftheMerino，wasgraduallyallowedtodieout。

Youseethatthesefactsillustrateperfectlywellwhatmaybedoneifyoutakecaretobreedfromstocksthataresimilartoeachother。

Afterhavinggotavariation，if，bycrossingavariationwiththeoriginalstock，youmultiplythatvariation，andthentakecaretokeepthatvariationdistinctfromtheoriginalstock，andmakethembreedtogether，——thenyoumayalmostcertainlyproducearacewhosetendencytocontinuethevariationisexceedinglystrong。

Thisiswhatiscalledselection。anditisbyexactlythesameprocessasthatbywhichSethWrightbredhisAnconsheep，thatourbreedsofcattle，dogs，andfowls，areobtained。Therearesomepossibilitiesofexception，butstill，speakingbroadly，Imaysaythatthisisthewayinwhichallourvariedracesofdomesticanimalshavearisen。andyoumustunderstandthatitisnotonepeculiarityoronecharacteristicaloneinwhichanimalsmayvary。Thereisnotasinglepeculiarityorcharacteristicofanykind，bodilyormental，inwhichoffspringmaynotvarytoacertainextentfromtheparentandotheranimals。

Amongourselvesthisiswellknown。Thesimplestphysicalpeculiarityismostlyreproduced。Iknowacaseofamanwhosewifehasthelobeofoneofherearsalittleflattened。Anordinaryobservermightscarcelynoticeit，andyeteveryoneofherchildrenhasanapproximationtothesamepeculiaritytosomeextent。Ifyoulookattheotherextreme，too，thegravestdiseases，suchasgout，scrofula，andconsumption，maybehandeddownwithjustthesamecertaintyandpersistenceaswenoticedintheperpetuationofthebandylegsoftheAnconsheep。

However，thesefactsarebestillustratedinanimals，andtheextentofthevariation，asiswellknown，isveryremarkableindogs。Forexample，therearesomedogsverymuchsmallerthanothers。indeed，thevariationissoenormousthatprobablythesmallestdogwouldbeaboutthesizeoftheheadofthelargest。thereareverygreatvariationsinthestructuralformsnotonlyoftheskeletonbutalsointheshapeoftheskull，andintheproportionsofthefaceandthedispositionoftheteeth。

ThePointer，theRetriever，Bulldog，andtheTerrier，differverygreatly，andyetthereiseveryreasontobelievethateveryoneoftheseraceshasarisenfromthesamesource，——thatallthemostimportantraceshavearisenbythisselectivebreedingfromaccidentalvariation。

Astillmorestrikingcaseofwhatmaybedonebyselectivebreeding，anditisabettercase，becausethereisnochanceofthatpartialinfusionoferrortowhichIalluded，hasbeenstudiedverycarefullybyMr。Darwin，——thecaseofthedomesticpigeons。Idaresaytheremaybesomeamongyouwhomaybepigeon’fanciers’，andIwishyoutounderstandthatinapproachingthesubject，Iwouldspeakwithallhumilityandhesitation，asIregrettosaythatIamnotapigeonfancier。Iknowitisagreatartandmystery，andathinguponwhichamanmustnotspeaklightly。butIshallendeavour，asfarasmyunderstandinggoes，togiveyouasummaryofthepublishedandunpublishedinformationwhichIhavegainedfromMr。Darwin。

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