Ihavediscussedtheprobableoriginofdomesticpigeonsatsome，yetquiteinsufficient，length。becausewhenIfirstkeptpigeonsandwatchedtheseveralkinds，knowingwellhowtruetheybred，Ifeltfullyasmuchdifficultyinbelievingthattheycouldeverhavedescendedfromacommonparent，asanynaturalistcouldincomingtoasimilarconclusioninregardtothemanyspeciesoffinches，orotherlargegroupsofbirds，innature。

Onecircumstancehasstruckmemuch。namely，thatallthebreedersofthevariousdomesticanimalsandthecultivatorsofplants，withwhomIhaveeverconversed，orwhosetreatisesIhaveread，arefirmlyconvincedthattheseveralbreedstowhicheachhasattended，aredescendedfromsomanyaboriginallydistinctspecies。Ask，asIhaveasked，acelebratedraiserofHerefordcattle，whetherhiscattlemightnothavedescendedfromlonghorns，andhewilllaughyoutoscorn。Ihavenevermetapigeon，orpoultry，orduck，orrabbitfancier，whowasnotfullyconvincedthateachmainbreedwasdescendedfromadistinctspecies。VanMons，inhistreatiseonpearsandapples，showshowutterlyhedisbelievesthattheseveralsorts，forinstanceaRibston-pippinorCodlin-apple，couldeverhaveproceededfromtheseedsofthesametree。Innumerableotherexamplescouldbegiven。

Theexplanation，Ithink，issimple：fromlong-continuedstudytheyarestronglyimpressedwiththedifferencesbetweentheseveralraces。andthoughtheywellknowthateachracevariesslightly，fortheywintheirprizesbyselectingsuchslightdifferences，yettheyignoreallgeneralarguments，andrefusetosumupintheirmindsslightdifferencesaccumulatedduringmanysuccessivegenerations。Maynotthosenaturalistswho，knowingfarlessofthelawsofinheritancethandoesthebreeder，andknowingnomorethanhedoesoftheintermediatelinksinthelonglinesofdescent，yetadmitthatmanyofourdomesticraceshavedescendedfromthesameparentsmaytheynotlearnalessonofcaution，whentheyderidetheideaofspeciesinastateofnaturebeinglinealdescendantsofotherspecies？SelectionLetusnowbrieflyconsiderthestepsbywhichdomesticraceshavebeenproduced，eitherfromoneorfromseveralalliedspecies。Somelittleeffectmay，perhaps，beattributedtothedirectactionoftheexternalconditionsoflife，andsomelittletohabit。buthewouldbeaboldmanwhowouldaccountbysuchagenciesforthedifferencesofadrayandracehorse，agreyhoundandbloodhound，acarrierandtumblerpigeon。Oneofthemostremarkablefeaturesinourdomesticatedracesisthatweseeinthemadaptation，notindeedtotheanimal’sorplant’sowngood，buttoman’suseorfancy。

Somevariationsusefultohimhaveprobablyarisensuddenly，orbyonestep。manybotanists，forinstance，believethatthefuller’steazle，withitshooks，whichcannotberivalledbyanymechanicalcontrivance，isonlyavarietyofthewildDipsacus。andthisamountofchangemayhavesuddenlyariseninaseedling。Soithasprobablybeenwiththeturnspitdog。andthisisknowntohavebeenthecasewiththeanconsheep。Butwhenwecomparethedray-horseandrace-horse，thedromedaryandcamel，thevariousbreedsofsheepfittedeitherforcultivatedlandormountainpasture，withthewoolofonebreedgoodforonepurpose，andthatofanotherbreedforanotherpurpose。whenwecomparethemanybreedsofdogs，eachgoodformaninverydifferentways。whenwecomparethegamecock，sopertinaciousinbattle，withotherbreedssolittlequarrelsome，with’everlastinglayers’whichneverdesiretosit，andwiththebantamsosmallandelegant。whenwecomparethehostofagricultural，culinary，orchard，andflower-gardenracesofplants，mostusefultomanatdifferentseasonsandfordifferentpurposes，orsobeautifulinhiseyes，wemust，Ithink，lookfurtherthantomerevariability。Wecannotsupposethatallthebreedsweresuddenlyproducedasperfectandasusefulaswenowseethem。indeed，inseveralcases，weknowthatthishasnotbeentheirhistory。Thekeyisman’spowerofaccumulativeselection：naturegivessuccessivevariations。manaddsthemupincertaindirectionsusefultohim。Inthissensehemaybesaidtomakeforhimselfusefulbreeds。

Thegreatpowerofthisprincipleofselectionisnothypothetical。

Itiscertainthatseveralofoureminentbreedershave，evenwithinasinglelifetime，modifiedtoalargeextentsomebreedsofcattleandsheep。

Inorderfullytorealisewhattheyhavedone，itisalmostnecessarytoreadseveralofthemanytreatisesdevotedtothissubject，andtoinspecttheanimals。Breedershabituallyspeakofananimal’sorganisationassomethingquiteplastic，whichtheycanmodelalmostastheyplease。IfIhadspaceIcouldquotenumerouspassagestothiseffectfromhighlycompetentauthorities。

Youatt，whowasprobablybetteracquaintedwiththeworksofagriculturaliststhanalmostanyotherindividual，andwhowashimselfaverygoodjudgeofananimal，speaksoftheprincipleofselectionas’thatwhichenablestheagriculturist，notonlytomodifythecharacterofhisflock，buttochangeitaltogether。Itisthemagician’swand，bymeansofwhichhemaysummonintolifewhateverformandmouldhepleases。’LordSomerville，speakingofwhatbreedershavedoneforsheep，says：’Itwouldseemasiftheyhadchalkedoutuponawallaformperfectinitself，andthenhadgivenitexistence。’Thatmostskilfulbreeder，SirJohnSebright，usedtosay，withrespecttopigeons，that’hewouldproduceanygivenfeatherinthreeyears，butitwouldtakehimsixyearstoobtainheadandbeak。’InSaxonytheimportanceoftheprincipleofselectioninregardtomerinosheepissofullyrecognised，thatmenfollowitasatrade：

thesheepareplacedonatableandarestudied，likeapicturebyaconnoisseur。

thisisdonethreetimesatintervalsofmonths，andthesheepareeachtimemarkedandclassed，sothattheverybestmayultimatelybeselectedforbreeding。

WhatEnglishbreedershaveactuallyeffectedisprovedbytheenormouspricesgivenforanimalswithagoodpedigree。andthesehavenowbeenexportedtoalmosteveryquarteroftheworld。Theimprovementisbynomeansgenerallyduetocrossingdifferentbreeds。allthebestbreedersarestronglyopposedtothispractice，exceptsometimesamongstcloselyalliedsub-breeds。Andwhenacrosshasbeenmade，theclosestselectionisfarmoreindispensableeventhaninordinarycases。Ifselectionconsistedmerelyinseparatingsomeverydistinctvariety，andbreedingfromit，theprinciplewouldbesoobviousashardlytobeworthnotice。butitsimportanceconsistsinthegreateffectproducedbytheaccumulationinonedirection，duringsuccessivegenerations，ofdifferencesabsolutelyinappreciablebyanuneducatedeyedifferenceswhichIforonehavevainlyattemptedtoappreciate。Notonemaninathousandhasaccuracyofeyeandjudgementsufficienttobecomeaneminentbreeder。Ifgiftedwiththesequalities，andhestudieshissubjectforyears，anddevoteshislifetimetoitwithindomitableperseverance，hewillsucceed，andmaymakegreatimprovements。ifhewantsanyofthesequalities，hewillassuredlyfail。

Fewwouldreadilybelieveinthenaturalcapacityandyearsofpracticerequisitetobecomeevenaskilfulpigeon-fancier。

Thesameprinciplesarefollowedbyhorticulturists。butthevariationsarehereoftenmoreabrupt。Noonesupposesthatourchoicestproductionshavebeenproducedbyasinglevariationfromtheaboriginalstock。Wehaveproofsthatthisisnotsoinsomecases，inwhichexactrecordshavebeenkept。thus，togiveaverytriflinginstance，thesteadily-increasingsizeofthecommongooseberrymaybequoted。Weseeanastonishingimprovementinmanyflorists’flowers，whentheflowersofthepresentdayarecomparedwithdrawingsmadeonlytwentyorthirtyyearsago。Whenaraceofplantsisonceprettywellestablished，theseed-raisersdonotpickoutthebestplants，butmerelygoovertheirseed-beds，andpullupthe’rogues，’astheycalltheplantsthatdeviatefromtheproperstandard。Withanimalsthiskindofselectionis，infact，alsofollowed。forhardlyanyoneissocarelessastoallowhisworstanimalstobreed。

Inregardtoplants，thereisanothermeansofobservingtheaccumulatedeffectsofselectionnamely，bycomparingthediversityofflowersinthedifferentvarietiesofthesamespeciesintheflower-garden。thediversityofleaves，pods，ortubers，orwhateverpartisvalued，inthekitchen-garden，incomparisonwiththeflowersofthesamevarieties。andthediversityoffruitofthesamespeciesintheorchard，incomparisonwiththeleavesandflowersofthesamesetofvarieties。Seehowdifferenttheleavesofthecabbageare，andhowextremelyaliketheflowers。howunliketheflowersoftheheartseaseare，andhowaliketheleaves。howmuchthefruitofthedifferentkindsofgooseberriesdifferinsize，colour，shape，andhairiness，andyettheflowerspresentveryslightdifferences。Itisnotthatthevarietieswhichdifferlargelyinsomeonepointdonotdifferatallinotherpoints。thisishardlyever，perhapsnever，thecase。Thelawsofcorrelationofgrowth，theimportanceofwhichshouldneverbeoverlooked，willensuresomedifferences。but，asageneralrule，Icannotdoubtthatthecontinuedselectionofslightvariations，eitherintheleaves，theflowers，orthefruit，willproduceracesdifferingfromeachotherchieflyinthesecharacters。

Itmaybeobjectedthattheprincipleofselectionhasbeenreducedtomethodicalpracticeforscarcelymorethanthree-quartersofacentury。

ithascertainlybeenmoreattendedtooflateyears，andmanytreatiseshavebeenpublishedonthesubject。andtheresult，Imayadd，hasbeen，inacorrespondingdegree，rapidandimportant。Butitisveryfarfromtruethattheprincipleisamoderndiscovery。Icouldgiveseveralreferencestothefullacknowledgementoftheimportanceoftheprincipleinworksofhighantiquity。InrudeandbarbarousperiodsofEnglishhistorychoiceanimalswereoftenimported，andlawswerepassedtopreventtheirexportation：

thedestructionofhorsesunderacertainsizewasordered，andthismaybecomparedtothe’roguing’ofplantsbynurserymen。TheprincipleofselectionIfinddistinctlygiveninanancientChineseencyclopaedia。

ExplicitrulesarelaiddownbysomeoftheRomanclassicalwriters。FrompassagesinGenesis，itisclearthatthecolourofdomesticanimalswasatthatearlyperiodattendedto。Savagesnowsometimescrosstheirdogswithwildcanineanimals，toimprovethebreed，andtheyformerlydidso，asisattestedbypassagesinPliny。ThesavagesinSouthAfricamatchtheirdraughtcattlebycolour，asdosomeoftheEsquimauxtheirteamsofdogs。LivingstoneshowshowmuchgooddomesticbreedsarevaluedbythenegroesoftheinteriorofAfricawhohavenotassociatedwithEuropeans。

Someofthesefactsdonotshowactualselection，buttheyshowthatthebreedingofdomesticanimalswascarefullyattendedtoinancienttimes，andisnowattendedtobythelowestsavages。Itwould，indeed，havebeenastrangefact，hadattentionnotbeenpaidtobreeding，fortheinheritanceofgoodandbadqualitiesissoobvious。

Atthepresenttime，eminentbreederstrybymethodicalselection，withadistinctobjectinview，tomakeanewstrainorsub-breed，superiortoanythingexistinginthecountry。But，forourpurpose，akindofSelection，whichmaybecalledUnconscious，andwhichresultsfromeveryonetryingtopossessandbreedfromthebestindividualanimals，ismoreimportant。

Thus，amanwhointendskeepingpointersnaturallytriestogetasgooddogsashecan，andafterwardsbreedsfromhisownbestdogs，buthehasnowishorexpectationofpermanentlyalteringthebreed。NeverthelessIcannotdoubtthatthisprocess，continuedduringcenturies，wouldimproveandmodifyanybreed，inthesamewayasBakewell，Collins，&amp。c。，bythisverysameprocess，onlycarriedonmoremethodically，didgreatlymodify，evenduringtheirownlifetimes，theformsandqualitiesoftheircattle。Slowandinsensiblechangesofthiskindcouldneverberecognisedunlessactualmeasurementsorcarefuldrawingsofthebreedsinquestionhadbeenmadelongago，whichmightserveforcomparison。Insomecases，however，unchangedorbutlittlechangedindividualsofthesamebreedmaybefoundinlessciviliseddistricts，wherethebreedhasbeenlessimproved。ThereisreasontobelievethatKingCharles’sspanielhasbeenunconsciouslymodifiedtoalargeextentsincethetimeofthatmonarch。

Somehighlycompetentauthoritiesareconvincedthatthesetterisdirectlyderivedfromthespaniel，andhasprobablybeenslowlyalteredfromit。

ItisknownthattheEnglishpointerhasbeengreatlychangedwithinthelastcentury，andinthiscasethechangehas，itisbelieved，beenchieflyeffectedbycrosseswiththefox-hound。butwhatconcernsusis，thatthechangehasbeeneffectedunconsciouslyandgradually，andyetsoeffectually，that，thoughtheoldSpanishpointercertainlycamefromSpain，MrBarrowhasnotseen，asIaminformedbyhim，anynativedoginSpainlikeourpointer。

Byasimilarprocessofselection，andbycarefultraining，thewholebodyofEnglishracehorseshavecometosurpassinfleetnessandsizetheparentArabstock，sothatthelatter，bytheregulationsfortheGoodwoodRaces，arefavouredintheweightstheycarry。LordSpencerandothershaveshownhowthecattleofEnglandhaveincreasedinweightandinearlymaturity，comparedwiththestockformerlykeptinthiscountry。BycomparingtheaccountsgiveninoldpigeontreatisesofcarriersandtumblerswiththesebreedsasnowexistinginBritain，India，andPersia，wecan，Ithink，clearlytracethestagesthroughwhichtheyhaveinsensiblypassed，andcometodiffersogreatlyfromtherock-pigeon。

Youattgivesanexcellentillustrationoftheeffectsofacourseofselection，whichmaybeconsideredasunconsciouslyfollowed，insofarthatthebreederscouldneverhaveexpectedorevenhavewishedtohaveproducedtheresultwhichensuednamely，theproductionoftwodistinctstrains。ThetwoflocksofLeicestersheepkeptbyMrBuckleyandMrBurgess，asMrYouattremarks，’havebeenpurelybredfromtheoriginalstockofMrBakewellforupwardsoffiftyyears。ThereisnotasuspicionexistinginthemindofanyoneatallacquaintedwiththesubjectthattheownerofeitherofthemhasdeviatedinanyoneinstancefromthepurebloodofMrBakewell’sflock，andyetthedifferencebetweenthesheeppossessedbythesetwogentlemenissogreatthattheyhavetheappearanceofbeingquitedifferentvarieties。’

Ifthereexistsavagessobarbarousasnevertothinkoftheinheritedcharacteroftheoffspringoftheirdomesticanimals，yetanyoneanimalparticularlyusefultothem，foranyspecialpurpose，wouldbecarefullypreservedduringfaminesandotheraccidents，towhichsavagesaresoliable，andsuchchoiceanimalswouldthusgenerallyleavemoreoffspringthantheinferiorones。sothatinthiscasetherewouldbeakindofunconsciousselectiongoingon。WeseethevaluesetonanimalsevenbythebarbariansofTierradelFuego，bytheirkillinganddevouringtheiroldwomen，intimesofdearth，asoflessvaluethantheirdogs。

Inplantsthesamegradualprocessofimprovement，throughtheoccasionalpreservationofthebestindividuals，whetherornotsufficientlydistincttoberankedattheirfirstappearanceasdistinctvarieties，andwhetherornottwoormorespeciesorraceshavebecomeblendedtogetherbycrossing，mayplainlyberecognisedintheincreasedsizeandbeautywhichwenowseeinthevarietiesoftheheartsease，rose，pelargonium，dahlia，andotherplants，whencomparedwiththeoldervarietiesorwiththeirparent-stocks。

Noonewouldeverexpecttogetafirst-rateheartseaseordahliafromtheseedofawildplant。Noonewouldexpecttoraiseafirst-ratemeltingpearfromtheseedofawildpear，thoughhemightsucceedfromapoorseedlinggrowingwild，ifithadcomefromagarden-stock。Thepear，thoughcultivatedinclassicaltimes，appears，fromPliny’sdescription，tohavebeenafruitofveryinferiorquality。Ihaveseengreatsurpriseexpressedinhorticulturalworksatthewonderfulskillofgardeners，inhavingproducedsuchsplendidresultsfromsuchpoormaterials。buttheart，Icannotdoubt，hasbeensimple，and，asfarasthefinalresultisconcerned，hasbeenfollowedalmostunconsciously。Ithasconsistedinalwayscultivatingthebestknownvariety，sowingitsseeds，and，whenaslightlybettervarietyhaschancedtoappear，selectingit，andsoonwards。Butthegardenersoftheclassicalperiod，whocultivatedthebestpeartheycouldprocure，neverthoughtwhatsplendidfruitweshouldeat。thoughweoweourexcellentfruit，insomesmalldegree，totheirhavingnaturallychosenandpreservedthebestvarietiestheycouldanywherefind。

Alargeamountofchangeinourcultivatedplants，thusslowlyandunconsciouslyaccumulated，explains，asIbelieve，thewell-knownfact，thatinavastnumberofcaseswecannotrecognise，andthereforedonotknow，thewildparent-stocksoftheplantswhichhavebeenlongestcultivatedinourflowerandkitchengardens。Ifithastakencenturiesorthousandsofyearstoimproveormodifymostofourplantsuptotheirpresentstandardofusefulnesstoman，wecanunderstandhowitisthatneitherAustralia，theCapeofGoodHope，noranyotherregioninhabitedbyquiteuncivilisedman，hasaffordedusasingleplantworthculture。Itisnotthatthesecountries，sorichinspecies，donotbyastrangechancepossesstheaboriginalstocksofanyusefulplants，butthatthenativeplantshavenotbeenimprovedbycontinuedselectionuptoastandardofperfectioncomparablewiththatgiventotheplantsincountriesancientlycivilised。

Inregardtothedomesticanimalskeptbyuncivilisedman，itshouldnotbeoverlookedthattheyalmostalwayshavetostrugglefortheirownfood，atleastduringcertainseasons。Andintwocountriesverydifferentlycircumstanced，individualsofthesamespecies，havingslightlydifferentconstitutionsorstructure，wouldoftensucceedbetterintheonecountrythanintheother，andthusbyaprocessof’naturalselection，’aswillhereafterbemorefullyexplained，twosub-breedsmightbeformed。This，perhaps，partlyexplainswhathasbeenremarkedbysomeauthors，namely，thatthevarietieskeptbysavageshavemoreofthecharacterofspeciesthanthevarietieskeptincivilisedcountries。

Ontheviewheregivenoftheall-importantpartwhichselectionbymanhasplayed，itbecomesatonceobvious，howitisthatourdomesticracesshowadaptationintheirstructureorintheirhabitstoman’swantsorfancies。Wecan，Ithink，furtherunderstandthefrequentlyabnormalcharacterofourdomesticraces，andlikewisetheirdifferencesbeingsogreatinexternalcharactersandrelativelysoslightininternalpartsororgans。Mancanhardlyselect，oronlywithmuchdifficulty，anydeviationofstructureexceptingsuchasisexternallyvisible。andindeedherarelycaresforwhatisinternal。Hecanneveractbyselection，exceptingonvariationswhicharefirstgiventohiminsomeslightdegreebynature。

Nomanwouldevertrytomakeafantail，tillhesawapigeonwithataildevelopedinsomeslightdegreeinanunusualmanner，orapoutertillhesawapigeonwithacropofsomewhatunusualsize。andthemoreabnormalorunusualanycharacterwaswhenitfirstappeared，themorelikelyitwouldbetocatchhisattention。Buttousesuchanexpressionastryingtomakeafantail，is，Ihavenodoubt，inmostcases，utterlyincorrect。

Themanwhofirstselectedapigeonwithaslightlylargertail，neverdreamedwhatthedescendantsofthatpigeonwouldbecomethroughlong-continued，partlyunconsciousandpartlymethodicalselection。Perhapstheparentbirdofallfantailshadonlyfourteentail-featherssomewhatexpanded，likethepresentJavafantail，orlikeindividualsofotheranddistinctbreeds，inwhichasmanyasseventeentail-feathershavebeencounted。

Perhapsthefirstpouter-pigeondidnotinflateitscropmuchmorethantheturbitnowdoestheupperpartofitsoesophagus，ahabitwhichisdisregardedbyallfanciers，asitisnotoneofthepointsofthebreed。

Norletitbethoughtthatsomegreatdeviationofstructurewouldbenecessarytocatchthefancier’seye：heperceivesextremelysmalldifferences，anditisinhumannaturetovalueanynovelty，howeverslight，inone’sownpossession。Normustthevaluewhichwouldformerlybesetonanyslightdifferencesintheindividualsofthesamespecies，bejudgedofbythevaluewhichwouldnowbesetonthem，afterseveralbreedshaveoncefairlybeenestablished。Manyslightdifferencesmight，andindeeddonow，ariseamongstpigeons，whicharerejectedasfaultsordeviationsfromthestandardofperfectionofeachbreed。Thecommongoosehasnotgivenrisetoanymarkedvarieties。hencetheThoulouseandthecommonbreed，whichdifferonlyincolour，thatmostfleetingofcharacters，havelatelybeenexhibitedasdistinctatourpoultry-shows。

Ithinktheseviewsfurtherexplainwhathassometimesbeennoticednamelythatweknownothingabouttheoriginorhistoryofanyofourdomesticbreeds。But，infact，abreed，likeadialectofalanguage，canhardlybesaidtohavehadadefiniteorigin。Amanpreservesandbreedsfromanindividualwithsomeslightdeviationofstructure，ortakesmorecarethanusualinmatchinghisbestanimalsandthusimprovesthem，andtheimprovedindividualsslowlyspreadintheimmediateneighbourhood。Butasyettheywillhardlyhaveadistinctname，andfrombeingonlyslightlyvalued，theirhistorywillbedisregarded。Whenfurtherimprovedbythesameslowandgradualprocess，theywillspreadmorewidely，andwillgetrecognisedassomethingdistinctandvaluable，andwillthenprobablyfirstreceiveaprovincialname。Insemi-civilisedcountries，withlittlefreecommunication，thespreadingandknowledgeofanynewsub-breedwillbeaslowprocess。Assoonasthepointsofvalueofthenewsub-breedareoncefullyacknowledged，theprinciple，asIhavecalledit，ofunconsciousselectionwillalwaystend，perhapsmoreatoneperiodthanatanother，asthebreedrisesorfallsinfashion，perhapsmoreinonedistrictthaninanother，accordingtothestateofcivilisationoftheinhabitantsslowlytoaddtothecharacteristicfeaturesofthebreed，whatevertheymaybe。

Butthechancewillbeinfinitelysmallofanyrecordhavingbeenpreservedofsuchslow，varying，andinsensiblechanges。

Imustnowsayafewwordsonthecircumstances，favourable，orthereverse，toman’spowerofselection。Ahighdegreeofvariabilityisobviouslyfavourable，asfreelygivingthematerialsforselectiontoworkon。notthatmereindividualdifferencesarenotamplysufficient，withextremecare，toallowoftheaccumulationofalargeamountofmodificationinalmostanydesireddirection。Butasvariationsmanifestlyusefulorpleasingtomanappearonlyoccasionally，thechanceoftheirappearancewillbemuchincreasedbyalargenumberofindividualsbeingkept。andhencethiscomestobeofthehighestimportancetosuccess。OnthisprincipleMarshallhasremarked，withrespecttothesheepofpartsofYorkshire，that’astheygenerallybelongtopoorpeople，andaremostlyinsmalllots，theynevercanbeimproved。’Ontheotherhand，nurserymen，fromraisinglargestocksofthesameplants，aregenerallyfarmoresuccessfulthanamateursingettingnewandvaluablevarieties。Thekeepingofalargenumberofindividualsofaspeciesinanycountryrequiresthatthespeciesshouldbeplacedunderfavourableconditionsoflife，soastobreedfreelyinthatcountry。Whentheindividualsofanyspeciesarescanty，alltheindividuals，whatevertheirqualitymaybe，willgenerallybeallowedtobreed，andthiswilleffectuallypreventselection。Butprobablythemostimportantpointofall，is，thattheanimalorplantshouldbesohighlyusefultoman，orsomuchvaluedbyhim，thattheclosestattentionshouldbepaidtoeventheslightestdeviationinthequalitiesorstructureofeachindividual。Unlesssuchattentionbepaidnothingcanbeeffected。

Ihaveseenitgravelyremarked，thatitwasmostfortunatethatthestrawberrybegantovaryjustwhengardenersbegantoattendcloselytothisplant。

Nodoubtthestrawberryhadalwaysvariedsinceitwascultivated，buttheslightvarietieshadbeenneglected。Assoon，however，asgardenerspickedoutindividualplantswithslightlylarger，earlier，orbetterfruit，andraisedseedlingsfromthem，andagainpickedoutthebestseedlingsandbredfromthem，then，thereappeared(aidedbysomecrossingwithdistinctspecies)thosemanyadmirablevarietiesofthestrawberrywhichhavebeenraisedduringthelastthirtyorfortyyears。

Inthecaseofanimalswithseparatesexes，facilityinpreventingcrossesisanimportantelementofsuccessintheformationofnewraces，atleast，inacountrywhichisalreadystockedwithotherraces。Inthisrespectenclosureofthelandplaysapart。Wanderingsavagesortheinhabitantsofopenplainsrarelypossessmorethanonebreedofthesamespecies。

Pigeonscanbematedforlife，andthisisagreatconveniencetothefancier，forthusmanyracesmaybekepttrue，thoughmingledinthesameaviary。

andthiscircumstancemusthavelargelyfavouredtheimprovementandformationofnewbreeds。Pigeons，Imayadd，canbepropagatedingreatnumbersandataveryquickrate，andinferiorbirdsmaybefreelyrejected，aswhenkilledtheyserveforfood。Ontheotherhand，cats，fromtheirnocturnalramblinghabits，cannotbematched，and，althoughsomuchvaluedbywomenandchildren，wehardlyeverseeadistinctbreedkeptup。suchbreedsaswedosometimesseearealmostalwaysimportedfromsomeothercountry，oftenfromislands。AlthoughIdonotdoubtthatsomedomesticanimalsvarylessthanothers，yettherarityorabsenceofdistinctbreedsofthecat，thedonkey，peacock，goose，&amp。c。，maybeattributedinmainparttoselectionnothavingbeenbroughtintoplay：incats，fromthedifficultyinpairingthem。indonkeys，fromonlyafewbeingkeptbypoorpeople，andlittleattentionpaidtotheirbreeding。inpeacocks，fromnotbeingveryeasilyrearedandalargestocknotkept。ingeese，frombeingvaluableonlyfortwopurposes，foodandfeathers，andmoreespeciallyfromnopleasurehavingbeenfeltinthedisplayofdistinctbreeds。

TosumupontheoriginofourDomesticRacesofanimalsandplants。

Ibelievethattheconditionsoflife，fromtheiractiononthereproductivesystem，aresofarofthehighestimportanceascausingvariability。I

donotbelievethatvariabilityisaninherentandnecessarycontingency，underallcircumstances，withallorganicbeings，assomeauthorshavethought。Theeffectsofvariabilityaremodifiedbyvariousdegreesofinheritanceandofreversion。Variabilityisgovernedbymanyunknownlaws，moreespeciallybythatofcorrelationofgrowth。Somethingmaybeattributedtothedirectactionoftheconditionsoflife。Somethingmustbeattributedtouseanddisuse。Thefinalresultisthusrenderedinfinitelycomplex。

Insomecases，Idonotdoubtthattheintercrossingofspecies，aboriginallydistinct，hasplayedanimportantpartintheoriginofourdomesticproductions。

Wheninanycountryseveraldomesticbreedshaveoncebeenestablished，theiroccasionalintercrossing，withtheaidofselection，has，nodoubt，largelyaidedintheformationofnewsub-breeds。buttheimportanceofthecrossingofvarietieshas，Ibelieve，beengreatlyexaggerated，bothinregardtoanimalsandtothoseplantswhicharepropagatedbyseed。

Inplantswhicharetemporarilypropagatedbycuttings，buds，&amp。c。，theimportanceofthecrossingbothofdistinctspeciesandofvarietiesisimmense。forthecultivatorherequitedisregardstheextremevariabilitybothofhybridsandmongrels，andthefrequentsterilityofhybrids。butthecasesofplantsnotpropagatedbyseedareoflittleimportancetous，fortheirenduranceisonlytemporary。OverallthesecausesofChangeIamconvincedthattheaccumulativeactionofSelection，whetherappliedmethodicallyandmorequickly，orunconsciouslyandmoreslowly，butmoreefficiently，isbyfarthepredominantpower。NextChapterTheOriginofSpecies-Chapter2TheOriginofSpeciesbyCharlesDarwinPreviousChapterNextChapterChapter2-VariationUnderNatureBEFOREapplyingtheprinciplesarrivedatinthelastchaptertoorganicbeingsinastateofnature，wemustbrieflydiscusswhethertheselatteraresubjecttoanyvariation。Totreatthissubjectatallproperly，alongcatalogueofdryfactsshouldbegiven。buttheseIshallreserveformyfuturework。NorshallIherediscussthevariousdefinitionswhichhavebeengivenofthetermspecies。Noonedefinitionhasasyetsatisfiedallnaturalists。yeteverynaturalistknowsvaguelywhathemeanswhenhespeaksofaspecies。Generallythetermincludestheunknownelementofadistinctactofcreation。Theterm’variety’isalmostequallydifficulttodefine。butherecommunityofdescentisalmostuniversallyimplied，thoughitcanrarelybeproved。Wehavealsowhatarecalledmonstrosities。

buttheygraduateintovarieties。ByamonstrosityIpresumeismeantsomeconsiderabledeviationofstructureinonepart，eitherinjurioustoornotusefultothespecies，andnotgenerallypropagated。Someauthorsusetheterm’variation’inatechnicalsense，asimplyingamodificationdirectlyduetothephysicalconditionsoflife。and’variations’inthissensearesupposednottobeinherited：butwhocansaythatthedwarfedconditionofshellsinthebrackishwatersoftheBaltic，ordwarfedplantsonAlpinesummits，orthethickerfurofananimalfromfarnorthwards，wouldnotinsomecasesbeinheritedforatleastsomefewgenerations？andinthiscaseIpresumethattheformwouldbecalledavariety。

Again，wehavemanyslightdifferenceswhichmaybecalledindividualdifferences，suchasareknownfrequentlytoappearintheoffspringfromthesameparents，orwhichmaybepresumedtohavethusarisen，frombeingfrequentlyobservedintheindividualsofthesamespeciesinhabitingthesameconfinedlocality。Noonesupposesthatalltheindividualsofthesamespeciesarecastintheverysamemould。Theseindividualdifferencesarehighlyimportantforus，astheyaffordmaterialsfornaturalselectiontoaccumulate，inthesamemannerasmancanaccumulateinanygivendirectionindividualdifferencesinhisdomesticatedproductions。Theseindividualdifferencesgenerallyaffectwhatnaturalistsconsiderunimportantparts。

butIcouldshowbyalongcatalogueoffacts，thatpartswhichmustbecalledimportant，whetherviewedunderaphysiologicalorclassificatorypointofview，sometimesvaryintheindividualsofthesamespecies。I

amconvincedthatthemostexperiencednaturalistwouldbesurprisedatthenumberofthecasesofvariability，eveninimportantpartsofstructure，whichhecouldcollectongoodauthority，asIhavecollected，duringacourseofyears。Itshouldberememberedthatsystematistsarefarfrompleasedatfindingvariabilityinimportantcharacters，andthattherearenotmanymenwhowilllaboriouslyexamineinternalandimportantorgans，andcomparetheminmanyspecimensofthesamespecies。Ishouldneverhaveexpectedthatthebranchingofthemainnervesclosetothegreatcentralganglionofaninsectwouldhavebeenvariableinthesamespecies。

Ishouldhaveexpectedthatchangesofthisnaturecouldhavebeeneffectedonlybyslowdegrees：yetquiterecentlyMrLubbockhasshownadegreeofvariabilityinthesemainnervesinCoccus，whichmayalmostbecomparedtotheirregularbranchingofthestemofatree。Thisphilosophicalnaturalist，Imayadd，hasalsoquiterecentlyshownthatthemusclesinthelarvaeofcertaininsectsareveryfarfromuniform。Authorssometimesargueinacirclewhentheystatethatimportantorgansnevervary。forthesesameauthorspracticallyrankthatcharacterasimportant(assomefewnaturalistshavehonestlyconfessed)whichdoesnotvary。and，underthispointofview，noinstanceofanyimportantpartvaryingwilleverbefound：butunderanyotherpointofviewmanyinstancesassuredlycanbegiven。

Thereisonepointconnectedwithindividualdifferences，whichseemstomeextremelyperplexing：Irefertothosegenerawhichhavesometimesbeencalled’protean’or’polymorphic，’inwhichthespeciespresentaninordinateamountofvariation。andhardlytwonaturalistscanagreewhichformstorankasspeciesandwhichasvarieties。WemayinstanceRubus，Rosa，andHieraciumamongstplants，severalgeneraofinsects，andseveralgeneraofBrachiopodshells。Inmostpolymorphicgenerasomeofthespecieshavefixedanddefinitecharacters。Generawhicharepolymorphicinonecountryseemtobe，withsomefewexceptions，polymorphicinothercountries，andlikewise，judgingfromBrachiopodshells，atformerperiodsoftime。

Thesefactsseemtobeveryperplexing，fortheyseemtoshowthatthiskindofvariabilityisindependentoftheconditionsoflife。Iaminclinedtosuspectthatweseeinthesepolymorphicgeneravariationsinpointsofstructurewhichareofnoserviceordisservicetothespecies，andwhichconsequentlyhavenotbeenseizedonandrendereddefinitebynaturalselection，ashereafterwillbeexplained。

Thoseformswhichpossessinsomeconsiderabledegreethecharacterofspecies，butwhicharesocloselysimilartosomeotherforms，oraresocloselylinkedtothembyintermediategradations，thatnaturalistsdonotliketorankthemasdistinctspecies，areinseveralrespectsthemostimportantforus。Wehaveeveryreasontobelievethatmanyofthesedoubtfulandclosely-alliedformshavepermanentlyretainedtheircharactersintheirowncountryforalongtime。foraslong，asfarasweknow，ashavegoodandtruespecies。practically，whenanaturalistcanunitetwoformstogetherbyothershavingintermediatecharacters，hetreatstheoneasavarietyoftheother，rankingthemostcommon，butsometimestheonefirstdescribed，asthespecies，andtheotherasthevariety。Butcasesofgreatdifficulty，whichIwillnothereenumerate，sometimesoccurindecidingwhetherornottorankoneformasavarietyofanother，evenwhentheyarecloselyconnectedbyintermediatelinks。norwillthecommonly-assumedhybridnatureoftheintermediatelinksalwaysremovethedifficulty。Inverymanycases，however，oneformisrankedasavarietyofanother，notbecausetheintermediatelinkshaveactuallybeenfound，butbecauseanalogyleadstheobservertosupposeeitherthattheydonowsomewhereexist，ormayformerlyhaveexisted。andhereawidedoorfortheentryofdoubtandconjectureisopened。

Hence，indeterminingwhetheraformshouldberankedasaspeciesoravariety，theopinionofnaturalistshavingsoundjudgementandwideexperienceseemstheonlyguidetofollow。Wemust，however，inmanycases，decidebyamajorityofnaturalists，forfewwell-markedandwell-knownvarietiescanbenamedwhichhavenotbeenrankedasspeciesbyatleastsomecompetentjudges。

Thatvarietiesofthisdoubtfulnaturearefarfromuncommoncannotbedisputed。ComparetheseveralflorasofGreatBritain，ofFranceoroftheUnitedStates，drawnupbydifferentbotanists，andseewhatasurprisingnumberofformshavebeenrankedbyonebotanistasgoodspecies，andbyanotherasmerevarieties。MrH。C。Watson，towhomIlieunderdeepobligationforassistanceofallkinds，hasmarkedforme182Britishplants，whicharegenerallyconsideredasvarieties，butwhichhaveallbeenrankedbybotanistsasspecies。andinmakingthislisthehasomittedmanytriflingvarieties，butwhichneverthelesshavebeenrankedbysomebotanistsasspecies，andhehasentirelyomittedseveralhighlypolymorphicgenera。

Undergenera，includingthemostpolymorphicforms，MrBabingtongives251species，whereasMrBenthamgivesonly112，adifferenceof139doubtfulforms！Amongstanimalswhichuniteforeachbirth，andwhicharehighlylocomotive，doubtfulforms，rankedbyonezoologistasaspeciesandbyanotherasavariety，canrarelybefoundwithinthesamecountry，butarecommoninseparatedareas。HowmanyofthosebirdsandinsectsinNorthAmericaandEurope，whichdifferveryslightlyfromeachother，havebeenrankedbyoneeminentnaturalistasundoubtedspecies，andbyanotherasvarieties，or，astheyareoftencalled，asgeographicalraces！Manyyearsago，whencomparing，andseeingotherscompare，thebirdsfromtheseparateislandsoftheGalapagosArchipelago，bothonewithanother，andwiththosefromtheAmericanmainland，Iwasmuchstruckhowentirelyvagueandarbitraryisthedistinctionbetweenspeciesandvarieties。OntheisletsofthelittleMadeiragrouptherearemanyinsectswhicharecharacterizedasvarietiesinMrWollaston’sadmirablework，butwhichitcannotbedoubtedwouldberankedasdistinctspeciesbymanyentomologists。EvenIrelandhasafewanimals，nowgenerallyregardedasvarieties，butwhichhavebeenrankedasspeciesbysomezoologists。SeveralmostexperiencedornithologistsconsiderourBritishredgrouseasonlyastrongly-markedraceofaNorwegianspecies，whereasthegreaternumberrankitasanundoubtedspeciespeculiartoGreatBritain。Awidedistancebetweenthehomesoftwodoubtfulformsleadsmanynaturaliststorankbothasdistinctspecies。butwhatdistance，ithasbeenwellasked，willsuffice？ifthatbetweenAmericaandEuropeisample，willthatbetweentheContinentandtheAzores，orMadeira，ortheCanaries，orIreland，besufficient？Itmustbeadmittedthatmanyforms，consideredbyhighly-competentjudgesasvarieties，havesoperfectlythecharacterofspeciesthattheyarerankedbyotherhighly-competentjudgesasgoodandtruespecies。Buttodiscusswhethertheyarerightlycalledspeciesorvarieties，beforeanydefinitionofthesetermshasbeengenerallyaccepted，isvainlytobeattheair。

Manyofthecasesofstrongly-markedvarietiesordoubtfulspecieswelldeserveconsideration。forseveralinterestinglinesofargument，fromgeographicaldistribution，analogicalvariation，hybridism，&amp。c。，havebeenbroughttobearontheattempttodeterminetheirrank。Iwillheregiveonlyasingleinstance，thewell-knownoneoftheprimroseandcowslip，orPrimulaverisandelatior。Theseplantsdifferconsiderablyinappearance。

theyhaveadifferentflavourandemitadifferentodour。theyfloweratslightlydifferentperiods。theygrowinsomewhatdifferentstations。theyascendmountainstodifferentheights。theyhavedifferentgeographicalranges。andlastly，accordingtoverynumerousexperimentsmadeduringseveralyearsbythatmostcarefulobserverG&auml。rtner，theycanbecrossedonlywithmuchdifficulty。Wecouldhardlywishforbetterevidenceofthetwoformsbeingspecificallydistinct。Ontheotherhand，theyareunitedbymanyintermediatelinks，anditisverydoubtfulwhethertheselinksarehybrids。andthereis，asitseemstome，anoverwhelmingamountofexperimentalevidence，showingthattheydescendfromcommonparents，andconsequentlymustberankedasvarieties。

Closeinvestigation，inmostcases，willbringnaturaliststoanagreementhowtorankdoubtfulforms。Yetitmustbeconfessed，thatitisinthebest-knowncountriesthatwefindthegreatestnumberofformsofdoubtfulvalue。Ihavebeenstruckwiththefact，thatifanyanimalorplantinastateofnaturebehighlyusefultoman，orfromanycausecloselyattracthisattention，varietiesofitwillalmostuniversallybefoundrecorded。

Thesevarieties，moreover，willbeoftenrankedbysomeauthorsasspecies。

Lookatthecommonoak，howcloselyithasbeenstudied。yetaGermanauthormakesmorethanadozenspeciesoutofforms，whichareverygenerallyconsideredasvarieties。andinthiscountrythehighestbotanicalauthoritiesandpracticalmencanbequotedtoshowthatthesessileandpedunculatedoaksareeithergoodanddistinctspeciesormerevarieties。

Whenayoungnaturalistcommencesthestudyofagroupoforganismsquiteunknowntohim，heisatfirstmuchperplexedtodeterminewhatdifferencestoconsiderasspecific，andwhatasvarieties。forheknowsnothingoftheamountandkindofvariationtowhichthegroupissubject。andthisshows，atleast，howverygenerallythereissomevariation。Butifheconfinehisattentiontooneclasswithinonecountry，hewillsoonmakeuphismindhowtorankmostofthedoubtfulforms。Hisgeneraltendencywillbetomakemanyspecies，forhewillbecomeimpressed，justlikethepigeonorpoultry-fancierbeforealludedto，withtheamountofdifferenceintheformswhichheiscontinuallystudying。andhehaslittlegeneralknowledgeofanalogicalvariationinothergroupsandinothercountries，bywhichtocorrecthisfirstimpressions。Asheextendstherangeofhisobservations，hewillmeetwithmorecasesofdifficulty。forhewillencounteragreaternumberofclosely-alliedforms。Butifhisobservationsbewidelyextended，hewillintheendgenerallybeenabledtomakeuphisownmindwhichtocallvarietiesandwhichspecies。buthewillsucceedinthisattheexpenseofadmittingmuchvariation，andthetruthofthisadmissionwilloftenbedisputedbyothernaturalists。When，moreover，hecomestostudyalliedformsbroughtfromcountriesnotnowcontinuous，inwhichcasehecanhardlyhopetofindtheintermediatelinksbetweenhisdoubtfulforms，hewillhavetotrustalmostentirelytoanalogy，andhisdifficultieswillrisetoaclimax。

Certainlynoclearlineofdemarcationhasasyetbeendrawnbetweenspeciesandsub-speciesthatis，theformswhichintheopinionofsomenaturalistscomeverynearto，butdonotquitearriveattherankofspecies。

or，again，betweensub-speciesandwell-markedvarieties，orbetweenlesservarietiesandindividualdifferences。Thesedifferencesblendintoeachotherinaninsensibleseries。andaseriesimpressesthemindwiththeideaofanactualpassage。

HenceIlookatindividualdifferences，thoughofsmallinteresttothesystematist，asofhighimportanceforus，asbeingthefirststeptowardssuchslightvarietiesasarebarelythoughtworthrecordinginworksonnaturalhistory。AndIlookatvarietieswhichareinanydegreemoredistinctandpermanent，asstepsleadingtomorestronglymarkedandmorepermanentvarieties。andattheselatter，asleadingtosub-species，andtospecies。Thepassagefromonestageofdifferencetoanotherandhigherstagemaybe，insomecases，duemerelytothelong-continuedactionofdifferentphysicalconditionsintwodifferentregions。butIhavenotmuchfaithinthisview。andIattributethepassageofavariety，fromastateinwhichitdiffersveryslightlyfromitsparenttooneinwhichitdiffersmore，totheactionofnaturalselectioninaccumulating(aswillhereafterbemorefullyexplained)differencesofstructureincertaindefinitedirections。HenceIbelieveawell-markedvarietymaybejustlycalledanincipientspecies。butwhetherthisbeliefbejustifiablemustbejudgedofbythegeneralweightoftheseveralfactsandviewsgiventhroughoutthiswork。

Itneednotbesupposedthatallvarietiesorincipientspeciesnecessarilyattaintherankofspecies。Theymaywhilstinthisincipientstatebecomeextinct，ortheymayendureasvarietiesforverylongperiods，ashasbeenshowntobethecasebyMrWollastonwiththevarietiesofcertainfossilland-shellsinMadeira。Ifavarietyweretoflourishsoastoexceedinnumberstheparentspecies，itwouldthenrankasthespecies，andthespeciesasthevariety。oritmightcometosupplantandexterminatetheparentspecies。orbothmightco-exist，andbothrankasindependentspecies。

Butweshallhereafterhavetoreturntothissubject。

FromtheseremarksitwillbeseenthatIlookatthetermspecies，asonearbitrarilygivenforthesakeofconveniencetoasetofindividualscloselyresemblingeachother，andthatitdoesnotessentiallydifferfromthetermvariety，whichisgiventolessdistinctandmorefluctuatingforms。Thetermvariety，again，incomparisonwithmereindividualdifferences，isalsoappliedarbitrarily，andformereconveniencesake。

Guidedbytheoreticalconsiderations，Ithoughtthatsomeinterestingresultsmightbeobtainedinregardtothenatureandrelationsofthespecieswhichvarymost，bytabulatingallthevarietiesinseveralwell-workedfloras。Atfirstthisseemedasimpletask。butMrH。C。Watson，towhomIammuchindebtedforvaluableadviceandassistanceonthissubject，soonconvincedmethatthereweremanydifficulties，asdidsubsequentlyDrHooker，eveninstrongerterms。Ishallreserveformyfutureworkthediscussionofthesedifficulties，andthetablesthemselvesoftheproportionalnumbersofthevaryingspecies。DrHookerpermitsmetoadd，thatafterhavingcarefullyreadmymanuscript，andexaminedthetables，hethinksthatthefollowingstatementsarefairlywellestablished。Thewholesubject，however，treatedasitnecessarilyhereiswithmuchbrevity，isratherperplexing，andallusionscannotbeavoidedtothe’struggleforexistence，’

’divergenceofcharacter，’andotherquestions，hereaftertobediscussed。

Alph。DeCandolleandothershaveshownthatplantswhichhaveverywiderangesgenerallypresentvarieties。andthismighthavebeenexpected，astheybecomeexposedtodiversephysicalconditions，andastheycomeintocompetition(which，asweshallhereaftersee，isafarmoreimportantcircumstance)withdifferentsetsoforganicbeings。Butmytablesfurthershowthat，inanylimitedcountry，thespecieswhicharemostcommon，thatisaboundmostinindividuals，andthespecieswhicharemostwidelydiffusedwithintheirowncountry(andthisisadifferentconsiderationfromwiderange，andtoacertainextentfromcommonness)，oftengiverisetovarietiessufficientlywell-markedtohavebeenrecordedinbotanicalworks。Henceitisthemostflourishing，or，astheymaybecalled，thedominantspecies，thosewhichrangewidelyovertheworld，arethemostdiffusedintheirowncountry，andarethemostnumerousinindividuals，whichoftenestproducewell-markedvarieties，or，asIconsiderthem，incipientspecies。Andthis，perhaps，mighthavebeenanticipated。for，asvarieties，inordertobecomeinanydegreepermanent，necessarilyhavetostrugglewiththeotherinhabitantsofthecountry，thespecieswhicharealreadydominantwillbethemostlikelytoyieldoffspringwhich，thoughinsomeslightdegreemodified，willstillinheritthoseadvantagesthatenabledtheirparentstobecomedominantovertheircompatriots。

IftheplantsinhabitingacountryanddescribedinanyFlorabedividedintotwoequalmasses，allthoseinthelargergenerabeingplacedononeside，andallthoseinthesmallergeneraontheotherside，asomewhatlargernumberoftheverycommonandmuchdiffusedordominantspecieswillbefoundonthesideofthelargergenera。This，again，mighthavebeenanticipated。forthemerefactofmanyspeciesofthesamegenusinhabitinganycountry，showsthatthereissomethingintheorganicorinorganicconditionsofthatcountryfavourabletothegenus。and，consequently，wemighthaveexpectedtohavefoundinthelargergenera，orthoseincludingmanyspecies，alargeproportionalnumberofdominantspecies。Butsomanycausestendtoobscurethisresult，thatIamsurprisedthatmytablesshowevenasmallmajorityonthesideofthelargergenera。Iwillherealludetoonlytwocausesofobscurity。Fresh-waterandsalt-lovingplantshavegenerallyverywiderangesandaremuchdiffused，butthisseemstobeconnectedwiththenatureofthestationsinhabitedbythem，andhaslittleornorelationtothesizeofthegeneratowhichthespeciesbelong。

Again，plantslowinthescaleoforganisationaregenerallymuchmorewidelydiffusedthanplantshigherinthescale。andhereagainthereisnocloserelationtothesizeofthegenera。Thecauseoflowly-organisedplantsrangingwidelywillbediscussedinourchapterongeographicaldistribution。

Fromlookingatspeciesasonlystrongly-markedandwell-definedvarieties，Iwasledtoanticipatethatthespeciesofthelargergeneraineachcountrywouldoftenerpresentvarieties，thanthespeciesofthesmallergenera。

forwherevermanycloselyrelatedspecies(i。e。speciesofthesamegenus)havebeenformed，manyvarietiesorincipientspeciesought，asageneralrule，tobenowforming。Wheremanylargetreesgrow，weexpecttofindsaplings。Wheremanyspeciesofagenushavebeenformedthroughvariation，circumstanceshavebeenfavourableforvariation。andhencewemightexpectthatthecircumstanceswouldgenerallybestillfavourabletovariation。Ontheotherhand，ifwelookateachspeciesasaspecialactofcreation，thereisnoapparentreasonwhymorevarietiesshouldoccurinagrouphavingmanyspecies，thaninonehavingfew。

TotestthetruthofthisanticipationIhavearrangedtheplantsoftwelvecountries，andthecoleopterousinsectsoftwodistricts，intotwonearlyequalmasses，thespeciesofthelargergeneraononeside，andthoseofthesmallergeneraontheotherside，andithasinvariablyprovedtobethecasethatalargerproportionofthespeciesonthesideofthelargergenerapresentvarieties，thanonthesideofthesmallergenera。

Moreover，thespeciesofthelargegenerawhichpresentanyvarieties，invariablypresentalargeraveragenumberofvarietiesthandothespeciesofthesmallgenera。Boththeseresultsfollowwhenanotherdivisionismade，andwhenallthesmallestgenera，withfromonlyonetofourspecies，areabsolutelyexcludedfromthetables。Thesefactsareofplainsignificationontheviewthatspeciesareonlystronglymarkedandpermanentvarieties。

forwhenevermanyspeciesofthesamegenushavebeenformed，orwhere，ifwemayusetheexpression，themanufactoryofspecieshasbeenactive，weoughtgenerallytofindthemanufactorystillinaction，moreespeciallyaswehaveeveryreasontobelievetheprocessofmanufacturingnewspeciestobeaslowone。Andthiscertainlyisthecase，ifvarietiesbelookedatasincipientspecies。formytablesclearlyshowasageneralrulethat，wherevermanyspeciesofagenushavebeenformed，thespeciesofthatgenuspresentanumberofvarieties，thatisofincipientspecies，beyondtheaverage。Itisnotthatalllargegeneraarenowvaryingmuch，andarethusincreasinginthenumberoftheirspecies，orthatnosmallgeneraarenowvaryingandincreasing。forifthishadbeenso，itwouldhavebeenfataltomytheory。inasmuchasgeologyplainlytellsusthatsmallgenerahaveinthelapseoftimeoftenincreasedgreatlyinsize。andthatlargegenerahaveoftencometotheirmaxima，declined，anddisappeared。

Allthatwewanttoshowis，thatwheremanyspeciesofagenushavebeenformed，onanaveragemanyarestillforming。andthisholdsgood。

Thereareotherrelationsbetweenthespeciesoflargegeneraandtheirrecordedvarietieswhichdeservenotice。Wehaveseenthatthereisnoinfalliblecriterionbywhichtodistinguishspeciesandwell-markedvarieties。

andinthosecasesinwhichintermediatelinkshavenotbeenfoundbetweendoubtfulforms，naturalistsarecompelledtocometoadeterminationbytheamountofdifferencebetweenthem，judgingbyanalogywhetherornottheamountsufficestoraiseoneorbothtotherankofspecies。Hencetheamountofdifferenceisoneveryimportantcriterioninsettlingwhethertwoformsshouldberankedasspeciesorvarieties。NowFrieshasremarkedinregardtoplants，andWestwoodinregardtoinsects，thatinlargegeneratheamountofdifferencebetweenthespeciesisoftenexceedinglysmall。

Ihaveendeavouredtotestthisnumericallybyaverages，and，asfarasmyimperfectresultsgo，theyalwaysconfirmtheview。Ihavealsoconsultedsomesagaciousandmostexperiencedobservers，and，afterdeliberation，theyconcurinthisview。Inthisrespect，therefore，thespeciesofthelargergeneraresemblevarieties，morethandothespeciesofthesmallergenera。Orthecasemaybeputinanotherway，anditmaybesaid，thatinthelargergenera，inwhichanumberofvarietiesorincipientspeciesgreaterthantheaveragearenowmanufacturing，manyofthespeciesalreadymanufacturedstilltoacertainextentresemblevarieties，fortheydifferfromeachotherbyalessthanusualamountofdifference。

Moreover，thespeciesofthelargegeneraarerelatedtoeachother，inthesamemannerasthevarietiesofanyonespeciesarerelatedtoeachother。Nonaturalistpretendsthatallthespeciesofagenusareequallydistinctfromeachother。theymaygenerallybedividedintosub-genera，orsections，orlessergroups。AsFrieshaswellremarked，littlegroupsofspeciesaregenerallyclusteredlikesatellitesaroundcertainotherspecies。Andwhatarevarietiesbutgroupsofforms，unequallyrelatedtoeachother，andclusteredroundcertainformsthatis，roundtheirparent-species？

Undoubtedlythereisonemostimportantpointofdifferencebetweenvarietiesandspecies。namely，thattheamountofdifferencebetweenvarieties，whencomparedwitheachotherorwiththeirparent-species，ismuchlessthanthatbetweenthespeciesofthesamegenus。Butwhenwecometodiscusstheprinciple，asIcallit，ofDivergenceofCharacter，weshallseehowthismaybeexplained，andhowthelesserdifferencesbetweenvarietieswilltendtoincreaseintothegreaterdifferencesbetweenspecies。

Thereisoneotherpointwhichseemstomeworthnotice。Varietiesgenerallyhavemuchrestrictedranges：thisstatementisindeedscarcelymorethanatruism，forifavarietywerefoundtohaveawiderrangethanthatofitssupposedparent-species，theirdenominationsoughttobereversed。

Butthereisalsoreasontobelieve，thatthosespecieswhichareverycloselyalliedtootherspecies，andinsofarresemblevarieties，oftenhavemuchrestrictedranges。Forinstance，MrH。C。Watsonhasmarkedformeinthewell-siftedLondonCatalogueofplants(4thedition)63plantswhicharethereinrankedasspecies，butwhichheconsidersassocloselyalliedtootherspeciesastobeofdoubtfulvalue：these63reputedspeciesrangeonanaverageover6。9oftheprovincesintowhichMrWatsonhasdividedGreatBritain。Now，inthissamecatalogue，53acknowledgedvarietiesarerecorded，andtheserangeover7。7provinces。whereas，thespeciestowhichthesevarietiesbelongrangeover14。3provinces。Sothattheacknowledgedvarietieshaveverynearlythesamerestrictedaveragerange，ashavethoseverycloselyalliedforms，markedformebyMrWatsonasdoubtfulspecies，butwhicharealmostuniversallyrankedbyBritishbotanistsasgoodandtruespecies。

Finally，then，varietieshavethesamegeneralcharactersasspecies，fortheycannotbedistinguishedfromspecies，except，firstly，bythediscoveryofintermediatelinkingforms，andtheoccurrenceofsuchlinkscannotaffecttheactualcharactersoftheformswhichtheyconnect。andexcept，secondly，byacertainamountofdifference，fortwoforms，ifdifferingverylittle，aregenerallyrankedasvarieties，notwithstandingthatintermediatelinkingformshavenotbeendiscovered。buttheamountofdifferenceconsiderednecessarytogivetotwoformstherankofspeciesisquiteindefinite。Ingenerahavingmorethantheaveragenumberofspeciesinanycountry，thespeciesofthesegenerahavemorethantheaveragenumberofvarieties。Inlargegenerathespeciesareapttobeclosely，butunequally，alliedtogether，forminglittleclustersroundcertainspecies。

Speciesverycloselyalliedtootherspeciesapparentlyhaverestrictedranges。Inalltheseseveralrespectsthespeciesoflargegenerapresentastronganalogywithvarieties。Andwecanclearlyunderstandtheseanalogies，ifspecieshaveonceexistedasvarieties，andhavethusoriginated：whereas，theseanalogiesareutterlyinexplicableifeachspecieshasbeenindependentlycreated。

Wehave，also，seenthatitisthemostflourishinganddominantspeciesofthelargergenerawhichonanaveragevarymost。andvarieties，asweshallhereaftersee，tendtobecomeconvertedintonewanddistinctspecies。

Thelargergenerathustendtobecomelarger。andthroughoutnaturetheformsoflifewhicharenowdominanttendtobecomestillmoredominantbyleavingmanymodifiedanddominantdescendants。Butbystepshereaftertobeexplained，thelargergeneraalsotendtobreakupintosmallergenera。

Andthus，theformsoflifethroughouttheuniversebecomedividedintogroupssubordinatetogroups。PreviousChapterNextChapterTheOriginofSpecies-Chapter3TheOriginofSpeciesbyCharlesDarwinPreviousChapterNextChapterChapter3-StruggleforExistenceBEF0REenteringonthesubjectofthischapter，Imustmakeafewpreliminaryremarks，toshowhowthestruggleforexistencebearsonNaturalSelection。

Ithasbeenseeninthelastchapterthatamongstorganicbeingsinastateofnaturethereissomeindividualvariability。indeedIamnotawarethatthishaseverbeendisputed。Itisimmaterialforuswhetheramultitudeofdoubtfulformsbecalledspeciesorsub-speciesorvarieties。whatrank，forinstance，thetwoorthreehundreddoubtfulformsofBritishplantsareentitledtohold，iftheexistenceofanywell-markedvarietiesbeadmitted。Butthemereexistenceofindividualvariabilityandofsomefewwell-markedvarieties，thoughnecessaryasthefoundationforthework，helpsusbutlittleinunderstandinghowspeciesariseinnature。Howhaveallthoseexquisiteadaptationsofonepartoftheorganisationtoanotherpart，andtotheconditionsoflife，andofonedistinctorganicbeingtoanotherbeing，beenperfected？Weseethesebeautifulco-adaptationsmostplainlyinthewoodpeckerandmissletoe。andonlyalittlelessplainlyinthehumblestparasitewhichclingstothehairsofaquadrupedorfeathersofabird。inthestructureofthebeetlewhichdivesthroughthewater。

intheplumedseedwhichiswaftedbythegentlestbreeze。inshort，weseebeautifuladaptationseverywhereandineverypartoftheorganicworld。

Again，itmaybeasked，howisitthatvarieties，whichIhavecalledincipientspecies，becomeultimatelyconvertedintogoodanddistinctspecies，whichinmostcasesobviouslydifferfromeachotherfarmorethandothevarietiesofthesamespecies？Howdothosegroupsofspecies，whichconstitutewhatarecalleddistinctgenera，andwhichdifferfromeachothermorethandothespeciesofthesamegenus，arise？Alltheseresults，asweshallmorefullyseeinthenextchapter，followinevitablyfromthestruggleforlife。Owingtothisstruggleforlife，anyvariation，howeverslightandfromwhatevercauseproceeding，ifitbeinanydegreeprofitabletoanindividualofanyspecies，initsinfinitelycomplexrelationstootherorganicbeingsandtoexternalnature，willtendtothepreservationofthatindividual，andwillgenerallybeinheritedbyitsoffspring。Theoffspring，also，willthushaveabetterchanceofsurviving，for，ofthemanyindividualsofanyspecieswhichareperiodicallyborn，butasmallnumbercansurvive。Ihavecalledthisprinciple，bywhicheachslightvariation，ifuseful，ispreserved，bythetermofNaturalSelection，inordertomarkitsrelationtoman’spowerofselection。Wehaveseenthatmanbyselectioncancertainlyproducegreatresults，andcanadaptorganicbeingstohisownuses，throughtheaccumulationofslightbutusefulvariations，giventohimbythehandofNature。ButNaturalSelection，asweshallhereaftersee，isapowerincessantlyreadyforaction，andisasimmeasurablysuperiortoman’sfeebleefforts，astheworksofNaturearetothoseofArt。

Wewillnowdiscussinalittlemoredetailthestruggleforexistence。

Inmyfutureworkthissubjectshallbetreated，asitwelldeserves，atmuchgreaterlength。TheelderDeCandolleandLyellhavelargelyandphilosophicallyshownthatallorganicbeingsareexposedtoseverecompetition。Inregardtoplants，noonehastreatedthissubjectwithmorespiritandabilitythanW。Herbert，DeanofManchester，evidentlytheresultofhisgreathorticulturalknowledge。Nothingiseasierthantoadmitinwordsthetruthoftheuniversalstruggleforlife，ormoredifficultatleastIhavefounditsothanconstantlytobearthisconclusioninmind。Yetunlessitbethoroughlyengrainedinthemind，Iamconvincedthatthewholeeconomyofnature，witheveryfactondistribution，rarity，abundance，extinction，andvariation，willbedimlyseenorquitemisunderstood。Webeholdthefaceofnaturebrightwithgladness，weoftenseesuperabundanceoffood。

wedonotsee，orweforget，thatthebirdswhichareidlysingingroundusmostlyliveoninsectsorseeds，andarethusconstantlydestroyinglife。orweforgethowlargelythesesongsters，ortheireggs，ortheirnestlingsaredestroyedbybirdsandbeastsofprey。wedonotalwaysbearinmind，thatthoughfoodmaybenowsuperabundant，itisnotsoatallseasonsofeachrecurringyear。

IshouldpremisethatIusethetermStruggleforExistenceinalargeandmetaphoricalsense，includingdependenceofonebeingonanother，andincluding(whichismoreimportant)notonlythelifeoftheindividual，butsuccessinleavingprogeny。Twocanineanimalsinatimeofdearth，maybetrulysaidtostrugglewitheachotherwhichshallgetfoodandlive。Butaplantontheedgeofadesertissaidtostruggleforlifeagainstthedrought，thoughmoreproperlyitshouldbesaidtobedependentonthemoisture。Aplantwhichannuallyproducesathousandseeds，ofwhichonanaverageonlyonecomestomaturity，maybemoretrulysaidtostrugglewiththeplantsofthesameandotherkindswhichalreadyclothetheground。

Themissletoeisdependentontheappleandafewothertrees，butcanonlyinafar-fetchedsensebesaidtostrugglewiththesetrees，foriftoomanyoftheseparasitesgrowonthesametree，itwilllanguishanddie。Butseveralseedlingmissletoes，growingclosetogetheronthesamebranch，maymoretrulybesaidtostrugglewitheachother。Asthemissletoeisdisseminatedbybirds，itsexistencedependsonbirds。anditmaymetaphoricallybesaidtostrugglewithotherfruit-bearingplants，inordertotemptbirdstodevourandthusdisseminateitsseedsratherthanthoseofotherplants。Intheseseveralsenses，whichpassintoeachother，Iuseforconveniencesakethegeneraltermofstruggleforexistence。

Astruggleforexistenceinevitablyfollowsfromthehighrateatwhichallorganicbeingstendtoincrease。Everybeing，whichduringitsnaturallifetimeproducesseveraleggsorseeds，mustsufferdestructionduringsomeperiodofitslife，andduringsomeseasonoroccasionalyear，otherwise，ontheprincipleofgeometricalincrease，itsnumberswouldquicklybecomesoinordinatelygreatthatnocountrycouldsupporttheproduct。Hence，asmoreindividualsareproducedthancanpossiblysurvive，theremustineverycasebeastruggleforexistence，eitheroneindividualwithanotherofthesamespecies，orwiththeindividualsofdistinctspecies，orwiththephysicalconditionsoflife。ItisthedoctrineofMalthusappliedwithmanifoldforcetothewholeanimalandvegetablekingdoms。forinthiscasetherecanbenoartificialincreaseoffood，andnoprudentialrestraintfrommarriage。Althoughsomespeciesmaybenowincreasing，moreorlessrapidly，innumbers，allcannotdoso，fortheworldwouldnotholdthem。

Thereisnoexceptiontotherulethateveryorganicbeingnaturallyincreasesatsohigharate，thatifnotdestroyed，theearthwouldsoonbecoveredbytheprogenyofasinglepair。Evenslow-breedingmanhasdoubledintwenty-fiveyears，andatthisrate，inafewthousandyears，therewouldliterallynotbestandingroomforhisprogeny。Linnaeushascalculatedthatifanannualplantproducedonlytwoseedsandthereisnoplantsounproductiveasthisandtheirseedlingsnextyearproducedtwo，andsoon，thenintwentyyearstherewouldbeamillionplants。Theelephantisreckonedtobetheslowestbreederofallknownanimals，andIhavetakensomepainstoestimateitsprobableminimumrateofnaturalincrease：itwillbeunderthemarktoassumethatitbreedswhenthirtyyearsold，andgoesonbreedingtillninetyyearsold，bringingforththreepairsofyounginthisinterval。ifthisbeso，attheendofthefifthcenturytherewouldbealivefifteenmillionelephants，descendedfromthefirstpair。

Butwehavebetterevidenceonthissubjectthanmeretheoreticalcalculations，namely，thenumerousrecordedcasesoftheastonishinglyrapidincreaseofvariousanimalsinastateofnature，whencircumstanceshavebeenfavourabletothemduringtwoorthreefollowingseasons。Stillmorestrikingistheevidencefromourdomesticanimalsofmanykindswhichhaverunwildinseveralpartsoftheworld：ifthestatementsoftherateofincreaseofslow-breedingcattleandhorsesinSouthAmerica，andlatterlyinAustralia，hadnotbeenwellauthenticated，theywouldhavebeenquiteincredible。

Soitiswithplants：casescouldbegivenofintroducedplantswhichhavebecomecommonthroughoutwholeislandsinaperiodoflessthantenyears，SeveraloftheplantsnowmostnumerousoverthewideplainsofLaPlata，clothingsquareleaguesofsurfacealmosttotheexclusionofallotherplants，havebeenintroducedfromEurope。andthereareplantswhichnowrangeinIndia，asIhearfromDrFalconer，fromCapeComorintotheHimalaya，whichhavebeenimportedfromAmericasinceitsdiscovery。Insuchcases，andendlessinstancescouldbegiven，noonesupposesthatthefertilityoftheseanimalsorplantshasbeensuddenlyandtemporarilyincreasedinanysensibledegree。Theobviousexplanationisthattheconditionsoflifehavebeenveryfavourable，andthattherehasconsequentlybeenlessdestructionoftheoldandyoung，andthatnearlyalltheyounghavebeenenabledtobreed。Insuchcasesthegeometricalratioofincrease，theresultofwhichneverfailstobesurprising，simplyexplainstheextraordinarilyrapidincreaseandwidediffusionofnaturalisedproductionsintheirnewhomes。

Inastateofnaturealmosteveryplantproducesseed，andamongstanimalsthereareveryfewwhichdonotannuallypair。Hencewemayconfidentlyassert，thatallplantsandanimalsaretendingtoincreaseatageometricalratio，thatallwouldmostrapidlystockeverystationinwhichtheycouldanyhowexist，andthatthegeometricaltendencytoincreasemustbecheckedbydestructionatsomeperiodoflife。Ourfamiliaritywiththelargerdomesticanimalstends，Ithink，tomisleadus：weseenogreatdestructionfallingonthem，andweforgetthatthousandsareannuallyslaughteredforfood，andthatinastateofnatureanequalnumberwouldhavesomehowtobedisposedof。

Theonlydifferencebetweenorganismswhichannuallyproduceeggsorseedsbythethousand，andthosewhichproduceextremelyfew，is，thattheslow-breederswouldrequireafewmoreyearstopeople，underfavourableconditions，awholedistrict，letitbeeversolarge。Thecondorlaysacoupleofeggsandtheostrichascore，andyetinthesamecountrythecondormaybethemorenumerousofthetwo：theFulmarpetrellaysbutoneegg，yetitisbelievedtobethemostnumerousbirdintheworld。

Oneflydepositshundredsofeggs，andanother，likethehippobosca，asingleone。butthisdifferencedoesnotdeterminehowmanyindividualsofthetwospeciescanbesupportedinadistrict。Alargenumberofeggsisofsomeimportancetothosespecies，whichdependonarapidlyfluctuatingamountoffood，foritallowsthemrapidlytoincreaseinnumber。Buttherealimportanceofalargenumberofeggsorseedsistomakeupformuchdestructionatsomeperiodoflife。andthisperiodinthegreatmajorityofcasesisanearlyone。Ifananimalcaninanywayprotectitsowneggsoryoung，asmallnumbermaybeproduced，andyettheaveragestockbefullykeptup。butifmanyeggsoryoungaredestroyed，manymustbeproduced，orthespecieswillbecomeextinct。Itwouldsufficetokeepupthefullnumberofatree，whichlivedonanaverageforathousandyears，ifasingleseedwereproducedonceinathousandyears，supposingthatthisseedwereneverdestroyed，andcouldbeensuredtogerminateinafittingplace。Sothatinallcases，theaveragenumberofanyanimalorplantdependsonlyindirectlyonthenumberofitseggsorseeds。

InlookingatNature，itismostnecessarytokeeptheforegoingconsiderationsalwaysinmindnevertoforgetthateverysingleorganicbeingaroundusmaybesaidtobestrivingtotheutmosttoincreaseinnumbers。thateachlivesbyastruggleatsomeperiodofitslife。thatheavydestructioninevitablyfallseitherontheyoungorold，duringeachgenerationoratrecurrentintervals。Lightenanycheck，mitigatethedestructioneversolittle，andthenumberofthespecieswillalmostinstantaneouslyincreasetoanyamount。ThefaceofNaturemaybecomparedtoayieldingsurface，withtenthousandsharpwedgespackedclosetogetheranddriveninwardsbyincessantblows，sometimesonewedgebeingstruck，andthenanotherwithgreaterforce。

Whatchecksthenaturaltendencyofeachspeciestoincreaseinnumberismostobscure。Lookatthemostvigorousspecies。byasmuchasitswarmsinnumbers，bysomuchwillitstendencytoincreasebestillfurtherincreased。

Weknownotexactlywhatthechecksareinevenonesingleinstance。Norwillthissurpriseanyonewhoreflectshowignorantweareonthishead，eveninregardtomankind，soincomparablybetterknownthananyotheranimal。Thissubjecthasbeenablytreatedbyseveralauthors，andIshall，inmyfuturework，discusssomeofthechecksatconsiderablelength，moreespeciallyinregardtotheferalanimalsofSouthAmerica。HereIwillmakeonlyafewremarks，justtorecalltothereader’smindsomeofthechiefpoints。Eggsorveryyounganimalsseemgenerallytosuffermost，butthisisnotinvariablythecase。Withplantsthereisavastdestructionofseeds，but，fromsomeobservationswhichIhavemade，Ibelievethatitistheseedlingswhichsuffermostfromgerminatingingroundalreadythicklystockedwithotherplants。Seedlings，also，aredestroyedinvastnumbersbyvariousenemies。forinstance，onapieceofgroundthreefeetlongandtwowide，dugandcleared，andwheretherecouldbenochokingfromotherplants，Imarkedalltheseedlingsofournativeweedsastheycameup，andoutofthe357nolessthan295weredestroyed，chieflybyslugsandinsects。Ifturfwhichhaslongbeenmown，andthecasewouldbethesamewithturfcloselybrowsedbyquadrupeds，belettogrow，themorevigorousplantsgraduallykillthelessvigorous，thoughfullygrown，plants：thusoutoftwentyspeciesgrowingonalittleplotofturf(threefeetbyfour)ninespeciesperishedfromtheotherspeciesbeingallowedtogrowupfreely。

Theamountoffoodforeachspeciesofcoursegivestheextremelimittowhicheachcanincrease。butveryfrequentlyitisnottheobtainingfood，buttheservingaspreytootheranimals，whichdeterminestheaveragenumbersofaspecies。Thus，thereseemstobelittledoubtthatthestockofpartridges，grouse，andharesonanylargeestatedependschieflyonthedestructionofvermin。IfnotoneheadofgamewereshotduringthenexttwentyyearsinEngland，and，atthesametime，ifnoverminweredestroyed，therewould，inallprobability，belessgamethanatpresent，althoughhundredsofthousandsofgameanimalsarenowannuallykilled。

Ontheotherhand，insomecases，aswiththeelephantandrhinoceros，nonearedestroyedbybeastsofprey：eventhetigerinIndiamostrarelydarestoattackayoungelephantprotectedbyitsdam。

Climateplaysanimportantpartindeterminingtheaveragenumbersofaspecies，andperiodicalseasonsofextremecoldordrought，Ibelievetobethemosteffectiveofallchecks。Iestimatedthatthewinterof1854-55destroyedfour-fifthsofthebirdsinmyowngrounds。andthisisatremendousdestruction，whenwerememberthattenpercent。isanextraordinarilyseveremortalityfromepidemicswithman。Theactionofclimateseemsatfirstsighttobequiteindependentofthestruggleforexistence。butinsofarasclimatechieflyactsinreducingfood，itbringsonthemostseverestrugglebetweentheindividuals，whetherofthesameorofdistinctspecies，whichsubsistonthesamekindoffood。Evenwhenclimate，forinstanceextremecold，actsdirectly，itwillbetheleastvigorous，orthosewhichhavegotleastfoodthroughtheadvancingwinter，whichwillsuffermost。Whenwetravelfromsouthtonorth，orfromadampregiontoadry，weinvariablyseesomespeciesgraduallygettingrarerandrarer，andfinallydisappearing。andthechangeofclimatebeingconspicuous，wearetemptedtoattributethewholeeffecttoitsdirectaction。Butthisisaveryfalseview：weforgetthateachspecies，evenwhereitmostabounds，isconstantlysufferingenormousdestructionatsomeperiodofitslife，fromenemiesorfromcompetitorsforthesameplaceandfood。

andiftheseenemiesorcompetitorsbeintheleastdegreefavouredbyanyslightchangeofclimate，theywillincreaseinnumbers，and，aseachareaisalreadyfullystockedwithinhabitants，theotherspecieswilldecrease。Whenwetravelsouthwardandseeaspeciesdecreasinginnumbers，wemayfeelsurethatthecauseliesquiteasmuchinotherspeciesbeingfavoured，asinthisonebeinghurt。Soitiswhenwetravelnorthward，butinasomewhatlesserdegree，forthenumberofspeciesofallkinds，andthereforeofcompetitors，decreasesnorthwards。henceingoingnorthward，orinascendingamountain，wefaroftenermeetwithstuntedforms，duetothedirectlyinjuriousactionofclimate，thanwedoinproceedingsouthwardsorindescendingamountain。WhenwereachtheArcticregions，orsnow-cappedsummits，orabsolutedeserts，thestruggleforlifeisalmostexclusivelywiththeelements。

Thatclimateactsinmainpartindirectlybyfavouringotherspecies，wemayclearlyseeintheprodigiousnumberofplantsinourgardenswhichcanperfectlywellendureourclimate，butwhichneverbecomenaturalised，fortheycannotcompetewithournativeplants，norresistdestructionbyournativeanimals。

Whenaspecies，owingtohighlyfavourablecircumstances，increasesinordinatelyinnumbersinasmalltract，epidemicsatleast，thisseemsgenerallytooccurwithourgameanimalsoftenensue：andherewehavealimitingcheckindependentofthestruggleforlife。Butevensomeoftheseso-calledepidemicsappeartobeduetoparasiticworms，whichhavefromsomecause，possiblyinpartthroughfacilityofdiffusionamongstthecrowdedanimals，beendisproportionablyfavoured：andherecomesinasortofstrugglebetweentheparasiteanditsprey。

Ontheotherhand，inmanycases，alargestockofindividualsofthesamespecies，relativelytothenumbersofitsenemies，isabsolutelynecessaryforitspreservation。Thuswecaneasilyraiseplentyofcornandrape-seed，&amp。c。，inourfields，becausetheseedsareingreatexcesscomparedwiththenumberofbirdswhichfeedonthem。norcanthebirds，thoughhavingasuperabundanceoffoodatthisoneseason，increaseinnumberproportionallytothesupplyofseed，astheirnumbersarecheckedduringwinter：butanyonewhohastried，knowshowtroublesomeitistogetseedfromafewwheatorothersuchplantsinagarden。Ihaveinthiscaselosteverysingleseed。Thisviewofthenecessityofalargestockofthesamespeciesforitspreservation，explains，Ibelieve，somesingularfactsinnature，suchasthatofveryrareplantsbeingsometimesextremelyabundantinthefewspotswheretheydooccur。andthatofsomesocialplantsbeingsocial，thatis，aboundinginindividuals，evenontheextremeconfinesoftheirrange。Forinsuchcases，wemaybelieve，thataplantcouldexistonlywheretheconditionsofitslifeweresofavourablethatmanycouldexisttogether，andthussaveeachotherfromutterdestruction。

Ishouldaddthatthegoodeffectsoffrequentintercrossing，andtheilleffectsofcloseinterbreeding，probablycomeintoplayinsomeofthesecases。butonthisintricatesubjectIwillnothereenlarge。

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