Thusitwouldappeartobedemonstrable，that，notwithstandingthegreatchangewhichisexhibitedbytheanimalpopulationoftheworldasawhole，certaintypeshavepersistedcomparativelywithoutalteration，andthequestionarises，Whatbearinghavesuchfactsastheseonournotionsofthehistoryoflifethroughgeologicaltime？Theanswertothisquestionwouldseemtodependontheviewwetakerespectingtheoriginofspeciesingeneral。Ifweassumethateveryspeciesofanimalandofplantwasformedbyadistinctactofcreativepower，andifthespecieswhichhaveincessantlysucceededoneanotherwereplacedupontheglobebytheseseparateacts，thentheexistenceofpersistenttypesissimplyanunintelligibleirregularity。Suchassumption，however，isasunsupportedbytraditionorbyRevelationasitisopposedbytheanalogyoftherestoftheoperationsofnature；andthosewhoimaginethat，byadoptinganysuchhypothesis，theyarestrengtheningthehandsoftheadvocatesoftheletteroftheMosaicaccount，aresimplymistaken。If，ontheotherhand，weadoptthathypothesistowhichalonethestudyofphysiologylendsanysupport——thathypothesiswhich，havingstruggledbeyondthereachofthosefatalsupporters，theTelliamedsandVestigiarians，whosonearlycauseditssuffocationbywindinearlyinfancy，isnowwinningatleasttheprovisionalassentofallthebestthinkersoftheday——thehypothesisthattheformsorspeciesoflivingbeings，asweknowthem，havebeenproducedbythegradualmodificationofpre-existingspecies——thentheexistenceofpersistenttypesseemstoteachusmuch。Justasasmallportionofagreatcurveappearsstraight，theapparentabsenceofchangeindirectionofthelinebeingtheexponentofthevastextentofthewhole，inproportiontothepartwesee；so，ifitbetruethatalllivingspeciesaretheresultofthemodificationofotherandsimplerforms，theexistenceoftheselittlealteredpersistenttypes，rangingthroughallgeologicaltime，mustindicatethattheyarebutthefinaltermsofanenormousseriesofmodifications，whichhadtheirbeinginthegreatlapseofpregeologictime，andarenowperhapsforeverlost。
Inotherwords，whenrightlystudied，theteachingsofpalaeontologyareatonewiththoseofphysicalgeology。OurfarthestexplorationscarryusbackbutalittlewayabovethemouthofthegreatriverofLife:
whereitarose，andbywhatchannelsthenobletidehasreachedthepointwhenitfirstbreaksuponourview，ishiddenfromus。
TheforegoingpagescontainthesubstanceofalecturedeliveredbeforetheRoyalInstitutionofGreatBritainmanymonthsago，andofcourselongbeforetheappearanceoftheremarkableworkonthe\"OriginofSpecies\"justpublishedbyMr。Darwin，whoarrivesatverysimilarconclusions。Although，inonesense，Imightfairlysaythatmyownviewshavebeenarrivedatindependently，IdonotknowthatIcanclaimanyequitablerighttopropertyinthem；forithaslongbeenmyprivilegetoenjoyMr。Darwin\'sfriendship，andtoprofitbycorrespondingwithhim，andby，tosomeextent，becomingacquaintedwiththeworkingsofhissingularlyoriginalandwell-storedmind。ItwasinconsequenceofmyknowledgeofthegeneraltenoroftheresearchesinwhichMr。Darwinhadbeensolongengaged；becauseIhadthemostcompleteconfidenceinhisperseverance，hisknowledge，and，aboveallthings，hishigh-mindedloveoftruth；and，moreover，becauseIfoundthatthebetterIbecameacquaintedwiththeopinionsofthebestnaturalistsregardingthevexedquestionofspecies，thelessfixedtheyseemedtobe，andthemoreinclinedtheyweretothehypothesisofgradualmodification，thatIventuredtospeakasstronglyasIhavedoneinthefinalparagraphsofmydiscourse。
Thus，mydawhavingsomanyborrowedplumes，IseenoimproprietyinmakingatailtothisbriefpaperbytakinganotherhandfuloffeathersfromMr。Darwin；endeavouringtopointoutinafewwords，infact，what，asIgatherfromtheperusalofhisbook，hisdoctrinesreallyare，andonwhatsortofbasistheyrest。AndIdothisthemorewillingly，asIobservethatalreadythehastiersortofcriticshavebegun，nottoreviewmyfriend\'sbook，buttohowloveritinamannerwhichmusttendgreatlytodistractthepublicmind。