wehavevariabilityinimportantparts，butthedifferenceshavenotbeenfixedbyselection。Mancaresfortheformandfleetnessofhisgreyhounds，forthesizeofhismastiffs，andformerlyforthestrengthofthejawinhisbulldogs，etc。;buthecaresnothingaboutthenumberoftheirmolarteethormammaeordigits;nordoweknowthatdifferencesintheseorgansarecorrelatedwith，orowetheirdevelopmentto，differencesinotherpartsofthebodyaboutwhichmandoescare。Thosewhohaveattendedtothesubjectofselectionwilladmitthat，naturehavinggivenvariability，man，ifhesochose，couldfixfivetoestothehinderfeetofcertainbreedsofdogs，ascertainlyastothefeetofhisDorkingfowls:hecouldprobablyfix，butwithmuchmoredifficulty，anadditionalpairofmolarteethineitherjaw，inthesamewayashehasgivenadditionalhornstocertainbreedsofsheep;ifhewishedtoproduceatoothlessbreedofdogs，havingtheso—calledTurkishdogwithitsimperfectteethtoworkon，hecouldprobablydoso，forhehassucceededinmakinghornlessbreedsofcattleandsheep。
Withrespecttotheprecisecausesandstepsbywhichtheseveralracesofdogshavecometodiffersogreatlyfromeachother，weare，asinmostothercases，profoundlyignorant。Wemayattributepartofthedifferenceinexternalformandconstitutiontoinheritancefromdistinctwildstocks，thatistochangeseffectedundernaturebeforedomestication。Wemustattributesomethingtothecrossingoftheseveraldomesticandnaturalraces。Ishall，however，soonrecurtothecrossingofraces。Wehavealreadyseenhowoftensavagescrosstheirdogswithwildnativespecies;
andPennantgivesacuriousaccount（1/74。’HistoryofQuadrupeds’1793
volume1page238。）ofthemannerinwhichFochabers，inScotland，wasstocked\"withamultitudeofcursofamostwolfishaspect\"fromasinglehybrid—wolfbroughtintothatdistrict。
Itwouldappearthatclimatetoacertainextentdirectlymodifiestheformsofdogs。WehavelatelyseenthatseveralofourEnglishbreedscannotliveinIndia，anditispositivelyassertedthatwhenbredthereforafewgenerationstheydegeneratenotonlyintheirmentalfaculties，butinform。CaptainWilliamson（1/75。’OrientalFieldSports’quotedbyYouatt’TheDog’page15。），whocarefullyattendedtothissubject，statesthat\"houndsarethemostrapidintheirdecline;\"\"greyhoundsandpointers，also，rapidlydecline。\"Butspaniels，aftereightorninegenerations，andwithoutacrossfromEurope，areasgoodastheirancestors。Dr。Falconerinformsmethatbulldogs，whichhavebeenknown，whenfirstbroughtintothecountry，topindownevenanelephantbyitstrunk，notonlyfalloffaftertwoorthreegenerationsinpluckandferocity，butlosetheunder—hungcharacteroftheirlowerjaws;theirmuzzlesbecomefinerandtheirbodieslighter。EnglishdogsimportedintoIndiaaresovaluablethatprobablyduecarehasbeentakentopreventtheircrossingwithnativedogs;sothatthedeteriorationcannotbethusaccountedfor。TheRev。R。Everestinformsmethatheobtainedapairofsetters，borninIndia，whichperfectlyresembledtheirScotchparents:heraisedseverallittersfromtheminDelhi，takingthemoststringentprecautionstopreventacross，butheneversucceeded，thoughthiswasonlythesecondgenerationinIndia，inobtainingasingleyoungdoglikeitsparentsinsizeormake;theirnostrilsweremorecontracted，theirnosesmorepointed，theirsizeinferior，andtheirlimbsmoreslender。SoagainonthecoastofGuinea，dogs，accordingtoBosman，\"alterstrangely;