Thatapplicationofthesciencesofbiologyandgeology，whichiscommonlyknownaspalaeontology，tookitsorigininthemindofthefirstpersonwho，findingsomethinglikeashell，orabone，naturallyimbeddedingravelorrock，indulgedinspeculationsuponthenatureofthisthingwhichhehaddugout——this\"fossil\"——anduponthecauseswhichhadbroughtitintosuchaposition。Inthisrudimentaryform，ahighantiquitymaysafelybeascribedtopalaeontology，inasmuchasweknowthat，500yearsbeforetheChristianera，thephilosophicdoctrinesofXenophaneswereinfluencedbyhisobservationsuponthefossilremainsexposedinthequarriesofSyracuse。Fromthistimeforthnotonlythephilosophers，butthepoets，thehistorians，thegeographersofantiquityoccasionallyrefertofossils;
and，aftertherevivaloflearning，livelycontroversiesaroserespectingtheirrealnature。Buthardlymorethantwocenturieshaveelapsedsincethisfundamentalproblemwasfirstexhaustivelytreated;itwasonlyinthelastcenturythatthearchaeologicalvalueoffossils——theirimportance，Imean，asrecordsofthehistoryoftheearth——wasfullyrecognised;
thefirstadequateinvestigationofthefossilremainsofanylargegroupofvertebratedanimalsistobefoundinCuvier’s\"RecherchessurlesOssemensFossiles，\"completedin1822;
and，somodernisstratigraphicalpalaeontology，thatitsfounder，WilliamSmith，livedtoreceivethejustrecognitionofhisservicesbytheawardofthefirstWollastonMedalin1831。
But，althoughpalaeontologyisacomparativelyyouthfulscientificspeciality，themassofmaterialswithwhichithastodealisalreadyprodigious。Inthelastfiftyyearsthenumberofknownfossilremainsofinvertebratedanimalshasbeentrebledorquadrupled。Theworkofinterpretationofvertebratefossils，thefoundationsofwhichweresosolidlylaidbyCuvier，wascarriedon，withwonderfulvigourandsuccess，byAgassizinSwitzerland，byVonMeyerinGermany，andlast，butnotleast，byOweninthiscountry，while，inlateryears，amultitudeofworkershavelabouredinthesamefield。Inmanygroupsoftheanimalkingdomthenumberoffossilformsalreadyknownisasgreatasthatoftheexistingspecies。Insomecasesitismuchgreater;andthereareentireordersofanimalsoftheexistenceofwhichweshouldknownothingexceptfortheevidenceaffordedbyfossilremains。Withallthisitmaybesafelyassumedthat，atthepresentmoment，wearenotacquaintedwithatittleofthefossilswhichwillsoonerorlaterbediscovered。IfwemayjudgebytheprofusionyieldedwithinthelastfewyearsbytheTertiaryformationsofNorthAmerica，thereseemstobenolimittothemultitudeofmammalianremainstobeexpectedfromthatcontinent;
andanalogyleadsustoexpectsimilarrichesinEasternAsia，whenevertheTertiaryformationsofthatregionareascarefullyexplored。Again，wehave，asyet，almosteverythingtolearnrespectingtheterrestrialpopulationoftheMesozoicepoch;
anditseemsasiftheWesternterritoriesoftheUnitedStateswereabouttoproveasinstructiveinregardtothispointastheyhaveinrespectoftertiarylife。MyfriendProfessorMarshinformsmethat，withintwoyears，remainsofmorethan160
distinctindividualsofmammals，belongingtotwentyspeciesandninegenera，havebeenfoundinaspacenotlargerthanthefloorofagood—sizedroom;whilebedsofthesameagehaveyielded300reptiles，varyinginsizefromalengthof60feetor80feettothedimensionsofarabbit。
ThetaskwhichIhavesetmyselfto—nightistoendeavourtolaybeforeyou，asbrieflyaspossible，asketchofthesuccessivestepsbywhichourpresentknowledgeofthefactsofpalaeontologyandofthoseconclusionsfromthemwhichareindisputable，hasbeenattained;andIbegleavetoremindyou，attheoutset，thatinattemptingtosketchtheprogressofabranchofknowledgetowhichinnumerablelabourshavecontributed，mybusinessisratherwithgeneralisationsthanwithdetails。Itismyobjecttomarktheepochsofpalaeontology，nottorecountalltheeventsofitshistory。
ThatwhichIjustnowcalledthefundamentalproblemofpalaeontology，thequestionwhichhastobesettledbeforeanyothercanbeprofitablydiscussed，isthis，Whatisthenatureoffossils？Arethey，asthehealthycommonsenseoftheancientGreeksappearstohaveledthemtoassumewithouthesitation，theremainsofanimalsandplants？Orarethey，aswassogenerallymaintainedinthefifteenth，sixteenth，andseventeenthcenturies，merefiguredstones，portionsofmineralmatterwhichhaveassumedtheformsofleavesandshellsandbones，justasthoseportionsofmineralmatterwhichwecallcrystalstakeontheformofregulargeometricalsolids？
Or，again，arethey，asothersthought，theproductsofthegermsofanimalsandoftheseedsofplantswhichhavelosttheirway，asitwere，inthebowelsoftheearth，andhaveachievedonlyanimperfectandabortivedevelopment？Itiseasytosneeratourancestorsforbeingdisposedtorejectthefirstinfavourofoneorotherofthelasttwohypotheses;butitismuchmoreprofitabletotrytodiscoverwhythey，whowerereallynotonewhitlesssensiblepersonsthanourexcellentselves，shouldhavebeenledtoentertainviewswhichstrikeusasabsurd，Thebeliefinwhatiserroneouslycalledspontaneousgeneration，thatistosay，inthedevelopmentoflivingmatteroutofmineralmatter，apartfromtheagencyofpre—existinglivingmatter，asanordinaryoccurrenceatthepresentday——
whichisstillheldbysomeofus，wasuniversallyacceptedasanobvioustruthbythem。Theycouldpointtothearborescentformsassumedbyhoar—frostandbysundrymetallicmineralsasevidenceoftheexistenceinnatureofa\"plasticforce\"
competenttoenableinorganicmattertoassumetheformoforganisedbodies。Then，aseveryonewhoisfamiliarwithfossilsknows，theypresentinnumerablegradations，fromshellsandboneswhichexactlyresembletherecentobjects，tomassesofmerestonewhich，howeveraccuratelytheyrepeattheoutwardformoftheorganicbody，havenothingelseincommonwithit;
and，thence，tomeretracesandfaintimpressionsinthecontinuoussubstanceoftherock。Whatwenowknowtobetheresultsofthechemicalchangeswhichtakeplaceinthecourseoffossilisation，bywhichmineralissubstitutedfororganicsubstance，might，intheabsenceofsuchknowledge，befairlyinterpretedastheexpressionofaprocessofdevelopmentintheoppositedirection——fromthemineraltotheorganic。Moreover，inanagewhenitwouldhaveseemedthemostabsurdofparadoxestosuggestthatthegeneralleveloftheseaisconstant，whilethatofthesolidlandfluctuatesupanddownthroughthousandsoffeetinaseculargroundswell，itmaywellhaveappearedfarlesshazardoustoconceivethatfossilsaresportsofnaturethantoacceptthenecessaryalternative，thatalltheinlandregionsandhighlands，intherocksofwhichmarineshellshadbeenfound，hadoncebeencoveredbytheocean。Itisnotsosurprising，therefore，asitmayatfirstseem，thatalthoughsuchmenasLeonardodaVinciandBernardPalissytookjustviewsofthenatureoffossils，theopinionofthemajorityoftheircontemporariessetstronglytheotherway;noreventhaterrormaintaineditselflongafterthescientificgroundsofthetrueinterpretationoffossilshadbeenstated，inamannerthatleftnothingtobedesired，inthelatterhalfoftheseventeenthcentury。ThepersonwhorenderedthisgoodservicetopalaeontologywasNicolasSteno，professorofanatomyinFlorence，thoughaDanebybirth。Collectorsoffossilsatthatdaywerefamiliarwithcertainbodiestermed\"glossopetrae，\"andspeculationwasrifeastotheirnature。Inthefirsthalfoftheseventeenthcentury，FabioColonnahadtriedtoconvincehiscolleaguesofthefamousAccademiadeiLinceithattheglossopetraeweremerelyfossilsharks’teeth，buthisargumentsmadenoimpression。Fiftyyearslater，Stenore—openedthequestion，and，bydissectingtheheadofasharkandpointingouttheveryexactcorrespondenceofitsteethwiththeglossopetrae，leftnorationaldoubtastotheoriginofthelatter。Thusfar，theworkofStenowentlittlefurtherthanthatofColonna，butitfortunatelyoccurredtohimtothinkoutthewholesubjectoftheinterpretationoffossils，andtheresultofhismeditationswasthepublication，in1669，ofalittletreatisewiththeveryquainttitleof\"DeSolidointraSolidumnaturalitercontento。\"ThegeneralcourseofSteno’sargumentmaybestatedinafewwords。Fossilsaresolidbodieswhich，bysomenaturalprocess，havecometobecontainedwithinothersolidbodies，namely，therocksinwhichtheyareembedded;andthefundamentalproblemofpalaeontology，statedgenerally，isthis:\"Givenabodyendowedwithacertainshapeandproducedinaccordancewithnaturallaws，tofindinthatbodyitselftheevidenceoftheplaceandmannerofitsproduction。\"Theonlywayofsolvingthisproblemisbytheapplicationoftheaxiomthat\"likeeffectsimplylikecauses，\"
orasStenoputsit，inreferencetothisparticularcase，that\"bodieswhicharealtogethersimilarhavebeenproducedinthesameway。\"Hence，sincetheglossopetraearealtogethersimilartosharks’teeth，theymusthavebeenproducedbysharklikefishes;andsincemanyfossilshellscorrespond，downtotheminutestdetailsofstructure，withtheshellsofexistingmarineorfreshwateranimals，theymusthavebeenproducedbysimilaranimals;andthelikereasoningisappliedbyStenotothefossilbonesofvertebratedanimals，whetheraquaticorterrestrial。Totheobviousobjectionthatmanyfossilsarenotaltogethersimilartotheirlivinganalogues，differinginsubstancewhileagreeinginform，orbeingmerehollowsorimpressions，thesurfacesofwhicharefiguredinthesamewayasthoseofanimalorvegetableorganisms，Stenorepliesbypointingoutthechangeswhichtakeplaceinorganicremainsembeddedintheearth，andhowtheirsolidsubstancemaybedissolvedawayentirely，orreplacedbymineralmatter，untilnothingisleftoftheoriginalbutacast，animpression，orameretraceofitscontours。TheprinciplesofinvestigationthusexcellentlystatedandillustratedbyStenoin1669，arethosewhichhave，consciouslyorunconsciously，guidedtheresearchesofpalaeontologistseversince。Eventhatfeatofpalaeontologywhichhassopowerfullyimpressedthepopularimagination，thereconstructionofanextinctanimalfromatoothorabone，isbaseduponthesimplestimaginableapplicationofthelogicofSteno。Amoment’sconsiderationwillshow，infact，thatSteno’sconclusionthattheglossopetraearesharks’teethimpliesthereconstructionofananimalfromitstooth。Itisequivalenttotheassertionthattheanimalofwhichtheglossopetraearerelicshadtheformandorganisationofashark;thatithadaskull，avertebralcolumn，andlimbssimilartothosewhicharecharacteristicofthisgroupoffishes;thatitsheart，gills，andintestinespresentedthepeculiaritieswhichthoseofallsharksexhibit;nay，eventhatanyhardpartswhichitsintegumentcontainedwereofatotallydifferentcharacterfromthescalesofordinaryfishes。Theseconclusionsareascertainasanybaseduponprobablereasoningscanbe。Andtheyareso，simplybecauseaverylargeexperiencejustifiesusinbelievingthatteethofthisparticularformandstructureareinvariablyassociatedwiththepeculiarorganisationofsharks，andareneverfoundinconnectionwithotherorganisms。Whythisshouldbewearenotatpresentinapositioneventoimagine;wemusttakethefactasanempiricallawofanimalmorphology，thereasonofwhichmaypossiblybeonedayfoundinthehistoryoftheevolutionofthesharktribe，butforwhichitishopelesstoseekforanexplanationinordinaryphysiologicalreasonings。
Everyonepracticallyacquaintedwithpalaeontologyisawarethatitisnoteverytooth，noreverybone，whichenablesustoformajudgmentofthecharacteroftheanimaltowhichitbelonged;andthatitispossibletopossessmanyteeth，andevenalargeportionoftheskeletonofanextinctanimal，andyetbeunabletoreconstructitsskulloritslimbs。Itisonlywhenthetoothorbonepresentspeculiarities，whichweknowbypreviousexperiencetobecharacteristicofacertaingroup，thatwecansafelypredictthatthefossilbelongedtoananimalofthesamegroup。Anyonewhofindsacow’sgrindermaybeperfectlysurethatitbelongedtoananimalwhichhadtwocompletetoesoneachfootandruminated;anyonewhofindsahorse’sgrindermaybeassurethatithadonecompletetoeoneachfootanddidnotruminate;butifruminantsandhorseswereextinctanimalsofwhichnothingbutthegrindershadeverbeendiscovered，noamountofphysiologicalreasoningcouldhaveenabledustoreconstructeitheranimal，stilllesstohavedivinedthewidedifferencesbetweenthetwo。Cuvier，inthe\"DiscourssurlesRevolutionsdelaSurfaceduGlobe，\"strangelycreditshimself，andhaseversincebeencreditedbyothers，withtheinventionofanewmethodofpalaeontologicalresearch。
Butifyouwillturntothe\"RecherchessurlesOssemensFossiles\"andwatchCuvier，notspeculating，butworking，youwillfindthathismethodisneithermorenorlessthanthatofSteno。Ifhewasabletomakehisfamousprophecyfromthejawwhichlayuponthesurfaceofablockofstonetothepelvisofthesameanimalwhichlayhiddeninit，itwasnotbecauseeitherhe，oranyoneelse，knew，orknows，whyacertainformofjawis，asarule，constantlyaccompaniedbythepresenceofmarsupialbones，butsimplybecauseexperiencehasshownthatthesetwostructuresareco—ordinated。
Thesettlementofthenatureoffossilsledatoncetothenextadvanceofpalaeontology，viz。itsapplicationtothedecipheringofthehistoryoftheearth。Whenitwasadmittedthatfossilsareremainsofanimalsandplants，itfollowedthat，insofarastheyresembleterrestrial，orfreshwater，animalsandplants，theyareevidencesoftheexistenceofland，orfreshwater;and，insofarastheyresemblemarineorganisms，theyareevidencesoftheexistenceoftheseaatthetimeatwhichtheywerepartsofactuallylivinganimalsandplants。Moreover，intheabsenceofevidencetothecontrary，itmustbeadmittedthattheterrestrialorthemarineorganismsimpliedtheexistenceoflandorseaattheplaceinwhichtheywerefoundwhiletheywereyetliving。Infact，suchconclusionswereimmediatelydrawnbyeverybody，fromthetimeofXenophanesdownwards，whobelievedthatfossilswerereallyorganicremains。StenodiscussestheirvalueasevidenceofrepeatedalterationofmarineandterrestrialconditionsuponthesoilofTuscanyinamannerworthyofamoderngeologist。