Anothercase，thoughsomewhatdifferent，maybeheregiven，asitishighlyremarkable，andisestablishedonexcellentevidence。Kolreuterminutelydescribesfivevarietiesofthecommontobacco（16/25。’ZweiteForts。’s。53
namelyNicotianamajorvulgaris;（2）perennis;（3）transylvanica;（4）asub—
var。ofthelast;（5）majorlatifol。fl。alb。）whichwerereciprocallycrossed，andtheoffspringwereintermediateincharacterandasfertileastheirparents:fromthisfactKolreuterinferredthattheyarereallyvarieties;andnoone，asfarasIcandiscover，seemstohavedoubtedthatsuchisthecase。HealsocrossedreciprocallythesefivevarietieswithN。
glutinosa，andtheyyieldedverysterilehybrids;butthoseraisedfromthevar。perennis，whetherusedasthefatherormotherplant，werenotsosterileasthehybridsfromthefourothervarieties。（16/26。KolreuterwassomuchstruckwiththisfactthathesuspectedthatalittlepollenofN。glutinosainoneofhisexperimentsmighthaveaccidentallygotmingledwiththatofvar。perennis，andthusaideditsfertilisingpower。ButwenowknowconclusivelyfromGartner（’Bastarderz。’s。34，43）thatthepollenoftwospeciesneveractsCONJOINTLYonathirdspecies;stilllesswillthepollenofadistinctspecies，mingledwithaplant’sownpollen，ifthelatterbepresentinsufficientquantity，haveanyeffect。Thesoleeffectofminglingtwokindsofpollenistoproduceinthesamecapsuleseedswhichyieldplants，sometakingaftertheoneandsomeaftertheotherparent。）Sothatthesexualcapacityofthisonevarietyhascertainlybeeninsomedegreemodified，soastoapproachinnaturethatofN。glutinosa。（16/27。Mr。Scotthasmadesomeobservationsontheabsolutesterilityofapurpleandwhiteprimrose（Primulavulgaris）whenfertilisedbypollenfromthecommonprimrose（’JournalofProc。ofLinn。Soc。’volume81864page98）;buttheseobservationsrequireconfirmation。Iraisedanumberofpurple—floweredlong—
styledseedlingsfromseedkindlysentmebyMr。Scott，and，thoughtheywereallinsomedegreesterile，theyweremuchmorefertilewithpollentakenfromthecommonprimrosethanwiththeirownpollen。Mr。Scotthaslikewisedescribedaredequal—styledcowslip（P。verisibidpage106），whichwasfoundbyhimtobehighlysterilewhencrossedwiththecommoncowslip;butthiswasnotthecasewithseveralequal—styledredseedlingsraisedbymefromhisplant。Thisvarietyofthecowslippresentstheremarkablepeculiarityofcombiningmaleorgansineveryrespectlikethoseoftheshort—styledform，withfemaleorgansresemblinginfunctionandpartlyinstructurethoseofthelong—styledform;sothatwehavethesingularanomalyofthetwoformscombinedinthesameflower。Henceitisnotsurprisingthattheseflowersshouldbespontaneouslyself—fertileinahighdegree。）
Thesefactswithrespecttoplantsshowthatinsomefewcasescertainvarietieshavehadtheirsexualpowerssofarmodified，thattheycrosstogetherlessreadilyandyieldlessseedthanothervarietiesofthesamespecies。Weshallpresentlyseethatthesexualfunctionsofmostanimalsandplantsareeminentlyliabletobeaffectedbytheconditionsoflifetowhichtheyareexposed;andhereafterweshallbrieflydiscusstheconjointbearingofthisfact，andothers，onthedifferenceinfertilitybetweencrossedvarietiesandcrossedspecies。
DOMESTICATIONELIMINATESTHETENDENCYTOSTERILITYWHICHISGENERALWITH
SPECIESWHENCROSSED。
ThishypothesiswasfirstpropoundedbyPallas（16/28。’Act。Acad。St。
Petersburg’1780part2pages84，100。），andhasbeenadoptedbyseveralauthors。Icanfindhardlyanydirectfactsinitssupport;butunfortunatelynoonehascompared，inthecaseofeitheranimalsorplants，thefertilityofancientlydomesticatedvarieties，whencrossedwithadistinctspecies，withthatofthewildparent—specieswhensimilarlycrossed。Noonehascompared，forinstance，thefertilityofGallusbankivaandofthedomesticatedfowl，whencrossedwithadistinctspeciesofGallusorPhasianus;andtheexperimentwouldinallcasesbesurroundedbymanydifficulties。DureaudelaMalle，whohassocloselystudiedclassicalliterature，states（16/29。
’AnnalesdesSc。Nat。’tome211stseriespage61。）thatinthetimeoftheRomansthecommonmulewasproducedwithmoredifficultythanatthepresentday;butwhetherthisstatementmaybetrustedIknownot。Amuchmoreimportant，thoughsomewhatdifferent，caseisgivenbyM。Groenland（16/30。
’Bull。Bot。Soc。deFrance’December27，1861tome8page612。），namely，thatplants，knownfromtheirintermediatecharacterandsterilitytobehybridsbetweenAegilopsandwheat，haveperpetuatedthemselvesunderculturesince1857，WITHARAPIDBUTVARYINGINCREASEOFFERTILITYINEACHGENERATION。Inthefourthgenerationtheplants，stillretainingtheirintermediatecharacter，hadbecomeasfertileascommoncultivatedwheat。
TheindirectevidenceinfavourofthePallasiandoctrineappearstometobeextremelystrong。IntheearlierchaptersIhaveshownthatourvariousbreedsofthedogaredescendedfromseveralwildspecies;andthisprobablyisthecasewithsheep。TherecanbenodoubtthattheZebuorhumpedIndianoxbelongstoadistinctspeciesfromEuropeancattle:thelatter，moreover，aredescendedfromtwoforms，whichmaybecalledeitherspeciesorraces。Wehavegoodevidencethatourdomesticatedpigsbelongtoatleasttwospecifictypes，S。scrofaandindicus。Nowawidelyextendedanalogyleadstothebeliefthatiftheseseveralalliedspecies，whenfirstreclaimed，hadbeencrossed，theywouldhaveexhibited，bothintheirfirstunionsandintheirhybridoffspring，somedegreeofsterility。Nevertheless，theseveraldomesticatedracesdescendedfromthemarenowall，asfarascanbeascertained，perfectlyfertiletogether。Ifthisreasoningbetrustworthy，anditisapparentlysound，wemustadmitthePallasiandoctrinethatlong—
continueddomesticationtendstoeliminatethatsterilitywhichisnaturaltospecieswhencrossedintheiraboriginalstate。
ONINCREASEDFERTILITYFROMDOMESTICATIONANDCULTIVATION。
Increasedfertilityfromdomestication，withoutanyreferencetocrossing，maybeherebrieflyconsidered。Thissubjectbearsindirectlyontwoorthreepointsconnectedwiththemodificationoforganicbeings。AsBuffonlongagoremarked（16/31。QuotedbyIsid。GeoffroySt。Hilaire’Hist。NaturelleGenerale’tome3page476。SincethisMS。hasbeensenttopressafulldiscussiononthepresentsubjecthasappearedinMr。HerbertSpencer’s’PrinciplesofBiology’volume21867page457etseq。），domesticanimalsbreedoftenerintheyearandproducemoreyoungatabirththanwildanimalsofthesamespecies;they，also，sometimesbreedatanearlierage。Thecasewouldhardlyhavedeservedfurthernotice，hadnotsomeauthorslatelyattemptedtoshowthatfertilityincreasesanddecreasesinaninverseratiowiththeamountoffood。Thisstrangedoctrinehasapparentlyarisenfromindividualanimalswhensuppliedwithaninordinatequantityoffood，andfromplantsofmanykindswhengrownonexcessivelyrichsoil，asonadunghill，becomingsterile:buttothislatterpointIshallhaveoccasionpresentlytoreturn。Withhardlyanexception，ourdomesticatedanimals，whichhavebeenlonghabituatedtoaregularandcopioussupplyoffood，withoutthelabourofsearchingforit，aremorefertilethanthecorrespondingwildanimals。Itisnotorioushowfrequentlycatsanddogsbreed，andhowmanyyoungtheyproduceatabirth。Thewildrabbitissaidgenerallytobreedfourtimesyearly，andtoproduceeachtimeatmostsixyoung;thetamerabbitbreedssixorseventimesyearly，producingeachtimefromfourtoelevenyoung;andMr。HarrisonWeirtellsmeofacaseofeighteenyounghavingbeenproducedatabirth，allofwhichsurvived。Theferret，thoughgenerallysocloselyconfined，ismoreprolificthanitssupposedwildprototype。Thewildsowisremarkablyprolific;sheoftenbreedstwiceintheyear，andbearsfromfourtoeightandsometimeseventwelveyoung;butthedomesticsowregularlybreedstwiceayear，andwouldbreedoftenerifpermitted;andasowthatproduceslessthaneightatabirth\"isworthlittle，andthesoonersheisfattenedforthebutcherthebetter。\"Theamountoffoodaffectsthefertilityofthesameindividual:thussheep，whichonmountainsneverproducemorethanonelambatabirth，whenbroughtdowntolowlandpasturesfrequentlybeartwins。Thisdifferenceapparentlyisnotduetothecoldofthehigherland，forsheepandotherdomesticanimalsaresaidtobeextremelyprolificinLapland。Hardliving，also，retardstheperiodatwhichanimalsconceive;forithasbeenfounddisadvantageousinthenorthernislandsofScotlandtoallowcowstobearcalvesbeforetheyarefouryearsold。（16/32。Forcatsanddogsetc。seeBellingeriin’Annal。desSc。Nat。’2ndseries，Zoolog。tome12page155。ForferretsBechstein’NaturgeschichteDeutschlands’b。11801s。786，795。Forrabbitsdittos。1123，1131;andBronn’GeschichtederNatur。’b。2s。99。Formountainsheepdittos。102。Forthefertilityofthewildsow，seeBechstein’Naturgesch。Deutschlands’b。11801s。534;forthedomesticpigSidney’seditionof’YouattonthePig’1860page62。WithrespecttoLaplandseeAcerbi’TravelstotheNorthCape’Englishtranslationvolume2page222。
AbouttheHighlandcowssee’HoggonSheep’page263。）
[Birdsofferstillbetterevidenceofincreasedfertilityfromdomestication:
thehenofthewildGallusbankivalaysfromsixtoteneggs，anumberwhichwouldbethoughtnothingofwiththedomestichen。Thewildducklaysfromfivetoteneggs;thetameoneinthecourseoftheyearfromeightytoonehundred。Thewildgrey—laggooselaysfromfivetoeighteggs;thetamefromthirteentoeighteen，andshelaysasecondtime;asMr。Dixonhasremarked，\"high—feeding，care，andmoderatewarmthinduceahabitofprolificacywhichbecomesinsomemeasurehereditary。\"Whetherthesemi—domesticateddovecotepigeonismorefertilethanthewildrock—pigeon，C。livia，Iknownot;butthemorethoroughlydomesticatedbreedsarenearlytwiceasfertileasdovecotes:thelatter，however，whencagedandhighlyfed，becomeequallyfertilewithhousepigeons。IhearfromJudgeCatonthatthewildturkeyintheUnitedStatesdoesnotbreedwhenayearold，asthedomesticatedturkeysthereinvariablydo。Thepeahenaloneofdomesticatedbirdsisrathermorefertile，accordingtosomeaccounts，whenwildinitsnativeIndianhome，thaninEuropewhenexposedtoourmuchcolderclimate。（16/33。FortheeggsofGallusbankivaseeBlythin’AnnalsandMag。ofNat。Hist。’2ndseriesvolume11848page456。ForwildandtameducksMacgillivray’BritishBirds’volume5
page37;and’DieEnten’s。87。ForwildgeeseL。Lloyd’ScandinavianAdventures’volume21854page413;andfortamegeese’OrnamentalPoultry’byRev。E。S。Dixonpage139。OnthebreedingofPigeonsPistor’DasGanzederTaubenzucht’1831s。48;andBoitardandCorbie’LesPigeons’page158。Withrespecttopeacocks，accordingtoTemminck’Hist。Nat。Gen。desPigeons’etc。
1813tome2page41，thehenlaysinIndiaevenasmanyastwentyeggs;butaccordingtoJerdonandanotherwriterquotedinTegetmeier’PoultryBook’
1866pages280，282，shetherelaysonlyfromfourtonineorteneggs:inEnglandsheissaid，inthe’PoultryBook’tolayfiveorsix，butanotherwritersaysfromeighttotwelveeggs。）
Withrespecttoplants，noonewouldexpectwheattotillermore，andeacheartoproducemoregrain，inpoorthaninrichsoil;ortogetinpoorsoilaheavycropofpeasorbeans。Seedsvarysomuchinnumberthatitisdifficulttoestimatethem;butoncomparingbedsofcarrotsinanurserygardenwithwildplants，theformerseemedtoproduceabouttwiceasmuchseed。CultivatedcabbagesyieldedthriceasmanypodsbymeasureaswildcabbagesfromtherocksofSouthWales。Theexcessofberriesproducedbythecultivatedasparagusincomparisonwiththewildplantisenormous。Nodoubtmanyhighlycultivatedplants，suchaspears，pineapples，bananas，sugar—cane，etc。，arenearlyorquitesterile;andIaminclinedtoattributethissterilitytoexcessoffoodandtootherunnaturalconditions;buttothissubjectIshallrecur。]
Insomecases，aswiththepig，rabbit，etc。，andwiththoseplantswhicharevaluedfortheirseed，thedirectselectionofthemorefertileindividualshasprobablymuchincreasedtheirfertility;andinallcasesthismayhaveoccurredindirectly，fromthebetterchanceofsomeofthenumerousoffspringfromthemorefertileindividualshavingbeenpreserved。Butwithcats，ferrets，anddogs，andwithplantslikecarrots，cabbages，andasparagus，whicharenotvaluedfortheirprolificacy，selectioncanhaveplayedonlyasubordinatepart;andtheirincreasedfertilitymustbeattributedtothemorefavourableconditionsoflifeunderwhichtheyhavelongexisted。
CHAPTER2。XVII。
ONTHEGOODEFFECTSOFCROSSING，ANDONTHEEVILEFFECTSOFCLOSE
INTERBREEDING。
DEFINITIONOFCLOSEINTERBREEDING。
AUGMENTATIONOFMORBIDTENDENCIES。
GENERALEVIDENCEOFTHEGOODEFFECTSDERIVEDFROMCROSSING，ANDONTHEEVIL
EFFECTSFROMCLOSEINTERBREEDING。
CATTLE，CLOSELYINTERBRED;HALF—WILDCATTLELONGKEPTINTHESAMEPARKS。
SHEEP。
FALLOW—DEER。
DOGS，RABBITS，PIGS。
MAN，ORIGINOFHISABHORRENCEOFINCESTUOUSMARRIAGES。
FOWLS。
PIGEONS。
HIVE—BEES。
PLANTS，GENERALCONSIDERATIONSONTHEBENEFITSDERIVEDFROMCROSSING。
MELONS，FRUIT—TREES，PEAS，CABBAGES，WHEAT，ANDFOREST—TREES。
ONTHEINCREASEDSIZEOFHYBRIDPLANTS，NOTEXCLUSIVELYDUETOTHEIR
STERILITY。
ONCERTAINPLANTSWHICHEITHERNORMALLYORABNORMALLYARESELF—IMPOTENT，BUT
AREFERTILE，BOTHONTHEMALEANDFEMALESIDE，WHENCROSSEDWITHDISTINCT
INDIVIDUALSEITHEROFTHESAMEORANOTHERSPECIES。
CONCLUSION。
Thegaininconstitutionalvigour，derivedfromanoccasionalcrossbetweenindividualsofthesamevariety，butbelongingtodistinctfamilies，orbetweendistinctvarieties，hasnotbeensolargelyorsofrequentlydiscussed，ashavetheevileffectsoftoocloseinterbreeding。Buttheformerpointisthemoreimportantofthetwo，inasmuchastheevidenceismoredecisive。Theevilresultsfromcloseinterbreedingaredifficulttodetect，fortheyaccumulateslowly，anddiffermuchindegreewithdifferentspecies;
whilstthegoodeffectswhichalmostinvariablyfollowacrossarefromthefirstmanifest。Itshould，however，beclearlyunderstoodthattheadvantageofcloseinterbreeding，asfarastheretentionofcharacterisconcerned，isindisputable，andoftenoutweighstheevilofaslightlossofconstitutionalvigour。Inrelationtothesubjectofdomestication，thewholequestionisofsomeimportance，astoocloseinterbreedinginterfereswiththeimprovementofoldraces。ItisimportantasindirectlybearingonHybridism;andpossiblyontheextinctionofspecies，whenanyformhasbecomesorarethatonlyafewindividualsremainwithinaconfinedarea。Itbearsinanimportantmannerontheinfluenceoffreeintercrossing，inobliteratingindividualdifferences，andthusgivinguniformityofcharactertotheindividualsofthesameraceorspecies;forifadditionalvigourandfertilitybethusgained，thecrossedoffspringwillmultiplyandprevail，andtheultimateresultwillbefargreaterthanotherwisewouldhaveoccurred。Lastly，thequestionisofhighinterest，asbearingonmankind。Ishallthereforediscussthissubjectatfulllength。Asthefactswhichprovetheevileffectsofcloseinterbreedingaremorecopious，thoughlessdecisive，thanthoseonthegoodeffectsofcrossing，Ishall，undereachgroupofbeings，beginwiththeformer。
Thereisnodifficultyindefiningwhatismeantbyacross;butthisisbynomeanseasyinregardto\"breedinginandin\"or\"toocloseinterbreeding，\"
because，asweshallsee，differentspeciesofanimalsaredifferentlyaffectedbythesamedegreeofinterbreeding。Thepairingofafatheranddaughter，ormotherandson，orbrothersandsisters，ifcarriedonduringseveralgenerations，istheclosestpossibleformofinterbreeding。Butsomegoodjudges，forinstanceSirJ。Sebright，believethatthepairingofabrotherandsisterismuchcloserthanthatofparentsandchildren;forwhenthefatherismatchedwithhisdaughterhecrosses，asissaid，withonlyhalfhisownblood。Theconsequencesofcloseinterbreedingcarriedonfortoolongatime，are，asisgenerallybelieved，lossofsize，constitutionalvigour，andfertility，sometimesaccompaniedbyatendencytomalformation。Manifestevildoesnotusuallyfollowfrompairingthenearestrelationsfortwo，three，orevenfourgenerations;butseveralcausesinterferewithourdetectingtheevil——suchasthedeteriorationbeingverygradual，andthedifficultyofdistinguishingbetweensuchdirectevilandtheinevitableaugmentationofanymorbidtendencieswhichmaybelatentorapparentintherelatedparents。Ontheotherhand，thebenefitfromacross，evenwhentherehasnotbeenanyverycloseinterbreeding，isalmostinvariablyatonceconspicuous。Thereisgoodreasontobelieve，andthiswastheopinionofthatmostexperiencedobserverSirJ。Sebright（17/1。’TheArtofImprovingtheBreed，etc。’1809page16。），thattheevileffectsofcloseinterbreedingmaybecheckedorquitepreventedbytherelatedindividualsbeingseparatedforafewgenerationsandexposedtodifferentconditionsoflife。Thisconclusionisnowheldbymanybreeders;forinstanceMr。Carr（17/2。’TheHistoryoftheRiseandProgressoftheKillerby，etc。Herds’page41。）remarks，itisawell—known\"factthatachangeofsoilandclimateeffectsperhapsalmostasgreatachangeintheconstitutionaswouldresultfromaninfusionoffreshblood。\"Ihopetoshowinafutureworkthatconsanguinitybyitselfcountsfornothing，butactssolelyfromrelatedorganismsgenerallyhavingasimilarconstitution，andhavingbeenexposedinmostcasestosimilarconditions。
Thatanyevildirectlyfollowsfromtheclosestinterbreedinghasbeendeniedbymanypersons;butrarelybyanypracticalbreeder;andnever，asfarasI
know，byonewhohaslargelybredanimalswhichpropagatetheirkindquickly。
Manyphysiologistsattributetheevilexclusivelytothecombinationandconsequentincreaseofmorbidtendenciescommontobothparents;andthatthisisanactivesourceofmischieftherecanbenodoubt。Itisunfortunatelytoonotoriousthatmenandvariousdomesticanimalsendowedwithawretchedconstitution，andwithastronghereditarydispositiontodisease，ifnotactuallyill，arefullycapableofprocreatingtheirkind。Closeinterbreeding，ontheotherhand，ofteninducessterility;andthisindicatessomethingquitedistinctfromtheaugmentationofmorbidtendenciescommontobothparents。Theevidenceimmediatelytobegivenconvincesmethatitisagreatlawofnature，thatallorganicbeingsprofitfromanoccasionalcrosswithindividualsnotcloselyrelatedtotheminblood;andthat，ontheotherhand，long—continuedcloseinterbreedingisinjurious。
Variousgeneralconsiderationshavehadmuchinfluenceinleadingmetothisconclusion;butthereaderwillprobablyrelymoreonspecialfactsandopinions。Theauthorityofexperiencedobservers，evenwhentheydonotadvancethegroundsoftheirbelief，isofsomelittlevalue。Nowalmostallmenwhohavebredmanykindsofanimalsandhavewrittenonthesubject，suchasSirJ。Sebright，AndrewKnight，etc。（17/3。ForAndrewKnightseeA。Walkeron’Intermarriage’1838page227。SirJ。Sebright’Treatise’hasjustbeenquoted。），haveexpressedthestrongestconvictionontheimpossibilityoflong—continuedcloseinterbreeding。Thosewhohavecompiledworksonagriculture，andhaveassociatedmuchwithbreeders，suchasthesagaciousYouatt，Low，etc。，havestronglydeclaredtheiropiniontothesameeffect。
ProsperLucas，trustinglargelytoFrenchauthorities，hascometoasimilarconclusion。ThedistinguishedGermanagriculturistHermannvonNathusius，whohaswrittenthemostabletreatiseonthissubjectwhichIhavemetwith，concurs;andasIshallhavetoquotefromthistreatise，ImaystatethatNathusiusisnotonlyintimatelyacquaintedwithworksonagricultureinalllanguages，andknowsthepedigreesofourBritishbreedsbetterthanmostEnglishmen，buthasimportedmanyofourimprovedanimals，andishimselfanexperiencedbreeder。
Evidenceoftheevileffectsofcloseinterbreedingcanmostreadilybeacquiredinthecaseofanimals，suchasfowls，pigeons，etc。，whichpropagatequickly，and，frombeingkeptinthesameplace，areexposedtothesameconditions。NowIhaveinquiredofverymanybreedersofthesebirds，andI
havehithertonotmetwithasinglemanwhowasnotthoroughlyconvincedthatanoccasionalcrosswithanotherstrainofthesamesub—varietywasabsolutelynecessary。Mostbreedersofhighlyimprovedorfancybirdsvaluetheirownstrain，andaremostunwilling，attherisk，intheiropinion，ofdeterioration，tomakeacross。Thepurchaseofafirst—ratebirdofanotherstrainisexpensive，andexchangesaretroublesome;yetallbreeders，asfarasIcanhear，exceptingthosewhokeeplargestocksatdifferentplacesforthesakeofcrossing，aredrivenafteratimetotakethisstep。
Anothergeneralconsiderationwhichhashadgreatinfluenceonmymindis，thatwithallhermaphroditeanimalsandplants，whichitmighthavebeenthoughtwouldhaveperpetuallyfertilisedthemselvesandbeenthussubjectedforlongagestotheclosestinterbreeding，thereisnotasinglespecies，asfarasIcandiscover，inwhichthestructureensuresself—fertilisation。Onthecontrary，thereareinamultitudeofcases，asbrieflystatedinthefifteenthchapter，manifestadaptationswhichfavourorinevitablyleadtoanoccasionalcrossbetweenonehermaphroditeandanotherofthesamespecies;
andtheseadaptivestructuresareutterlypurposeless，asfaraswecansee，foranyotherend。
[WithCATTLEtherecanbenodoubtthatextremelycloseinterbreedingmaybelongcarriedonadvantageouslywithrespecttoexternalcharacters，andwithnomanifestevilasfarasconstitutionisconcerned。ThecaseofBakewell’sLonghorns，whichwerecloselyinterbredforalongperiod，hasoftenbeenquoted;yetYouattsays（17/4。’Cattle’page199。）thebreed\"hadacquiredadelicacyofconstitutioninconsistentwithcommonmanagement，\"and\"thepropagationofthespecieswasnotalwayscertain。\"ButtheShorthornsofferthemoststrikingcaseofcloseinterbreeding;forinstance，thefamousbullFavourite（whowashimselftheoffspringofahalf—brotherandsisterfromFoljambe）wasmatchedwithhisowndaughter，granddaughter，andgreat—
granddaughter;sothattheproduceofthislastunion，orthegreat—great—
granddaughter，had15—16ths，or93。75percentofthebloodofFavouriteinherveins。ThiscowwasmatchedwiththebullWellington，having62。5percentofFavouritebloodinhisveins，andproducedClarissa;ClarissawasmatchedwiththebullLancaster，having68。75ofthesameblood，andsheyieldedvaluableoffspring。（17/5。IgivethisontheauthorityofNathusius’UeberShorthornRindvieh’1857s。71，seealso’GardenersChronicle’1860page270。
ButMr。J。Storer，alargebreederofcattle，informsmethattheparentageofClarissaisnotwellauthenticated。Inthefirstvolumeofthe’HerdBook’shewasenteredashavingsixdescentsfromFavourite，\"whichwasapalpablemistake，\"andinallsubsequenteditionsshewasspokenofashavingonlyfourdescents。Mr。Storerdoubtsevenaboutthefour，asnonamesofthedamsaregiven。Moreover，Clarissabore\"onlytwobullsandoneheifer，andinthenextgenerationherprogenybecameextinct。\"AnalogouscasesofcloseinterbreedingaregiveninapamphletpublishedbyMr。C。MacknightandDr。H。Madden’OntheTruePrinciplesofBreeding’MelbourneAustralia1865。）NeverthelessCollings，whorearedtheseanimals，andwasastrongadvocateforclosebreeding，oncecrossedhisstockwithaGalloway，andthecowsfromthiscrossrealisedthehighestprices。Bates’sherdwasesteemedthemostcelebratedintheworld。Forthirteenyearshebredmostcloselyinandin;butduringthenextseventeenyears，thoughhehadthemostexaltednotionofthevalueofhisownstock，hethriceinfusedfreshbloodintohisherd:itissaidthathedidthis，nottoimprovetheformofhisanimals，butonaccountoftheirlessenedfertility。Mr。Bates’sownview，asgivenbyacelebratedbreeder（17/6。Mr。WilloughbyWoodin’Gardener’sChronicle’1855page411;and1860
page270。SeetheverycleartablesandpedigreesgiveninNathusius’Rindvieh’s。72—77。），was，that\"tobreedin—and—infromabadstockwasruinanddevastation;yetthatthepracticemaybesafelyfollowedwithincertainlimitswhentheparentssorelatedaredescendedfromfirst—rateanimals。\"WethusseethattherehasbeenmuchcloseinterbreedingwithShorthorns;butNathusius，afterthemostcarefulstudyoftheirpedigrees，saysthathecanfindnoinstanceofabreederwhohasstrictlyfollowedthispracticeduringhiswholelife。Fromthisstudyandhisownexperience，heconcludesthatcloseinterbreedingisnecessarytoennoblethestock;butthatineffectingthisthegreatestcareisnecessary，onaccountofthetendencytoinfertilityandweakness。Itmaybeadded，thatanotherhighauthority（17/7。Mr。Wright’JournalofRoyalAgricult。Soc。’volume71846page204。Mr。J。Downing（asuccessfulbreederofShorthornsinIreland）informsmethattheraisersofthegreatfamiliesofShorthornscarefullyconcealtheirsterilityandwantofconstitution。HeaddsthatMr。Bates，afterhehadbredhisherdin—and—inforsomeyears，\"lostinoneseasontwenty—eightcalvessolelyfromwantofconstitution。\"）assertsthatmanymorecalvesareborncripplesfromShorthornsthanfromotherandlesscloselyinterbredracesofcattle。
Althoughbycarefullyselectingthebestanimals（asNatureeffectuallydoesbythelawofbattle）closeinterbreedingmaybelongcarriedonwithcattle，yetthegoodeffectsofacrossbetweenalmostanytwobreedsisatonceshownbythegreatersizeandvigouroftheoffspring;asMr。Spoonerwritestome，\"crossingdistinctbreedscertainlyimprovescattleforthebutcher。\"Suchcrossedanimalsareofcourseofnovaluetothebreeder;buttheyhavebeenraisedduringmanyyearsinseveralpartsofEnglandtobeslaughtered（17/8。
’YouattonCattle’page202。）;andtheirmeritisnowsofullyrecognised，thatatfat—cattleshowsaseparateclasshasbeenformedfortheirreception。
ThebestfatoxatthegreatshowatIslingtonin1862wasacrossedanimal。
Thehalf—wildcattle，whichhavebeenkeptinBritishparksprobablyfor400
or500years，orevenforalongerperiod，havebeenadvancedbyCulleyandothersasacaseoflong—continuedinterbreedingwithinthelimitsofthesameherdwithoutanyconsequentinjury。WithrespecttothecattleatChillingham，thelateLordTankervilleownedthattheywerebadbreeders。（17/9。’ReportBritishAssoc。Zoolog。Sect。’1838。）Theagent，Mr。Hardy，estimates（inalettertome，datedMay，1861）thatintheherdofaboutfiftytheaveragenumberannuallyslaughtered，killedbyfighting，anddying，isaboutten，oroneinfive。Astheherdiskeptuptonearlythesameaveragenumber，theannualrateofincreasemustbelikewiseaboutoneinfive。Thebulls，Imayadd，engageinfuriousbattles，ofwhichbattlesthepresentLordTankervillehasgivenmeagraphicdescription，sothattherewillalwaysberigorousselectionofthemostvigorousmales。Iprocuredin1855fromMr。D。Gardner，agenttotheDukeofHamilton，thefollowingaccountofthewildcattlekeptintheDuke’sparkinLanarkshire，whichisabout200acresinextent。Thenumberofcattlevariesfromsixty—fivetoeighty;andthenumberannuallykilled（Ipresumebyallcauses）isfromeighttoten;sothattheannualrateofincreasecanhardlybemorethanoneinsix。NowinSouthAmerica，wheretheherdsarehalf—wild，andthereforeofferanearlyfairstandardofcomparison，accordingtoAzarathenaturalincreaseofthecattleonanestanciaisfromone—thirdtoone—fourthofthetotalnumber，oroneinbetweenthreeandfourandthis，nodoubt，appliesexclusivelytoadultanimalsfitforconsumption。Hencethehalf—wildBritishcattlewhichhavelonginterbredwithinthelimitsofthesameherdarerelativelyfarlessfertile。AlthoughinanunenclosedcountrylikeParaguaytheremustbesomecrossingbetweenthedifferentherds，yeteventheretheinhabitantsbelievethattheoccasionalintroductionofanimalsfromdistantlocalitiesisnecessarytoprevent\"degenerationinsizeanddiminutionoffertility。\"
（17/10。Azara’QuadrupedesduParaguay’tome2pages354，368。）ThedecreaseinsizefromancienttimesintheChillinghamandHamiltoncattlemusthavebeenprodigious，forProfessorRutimeyerhasshownthattheyarealmostcertainlythedescendantsofthegiganticBosprimigenius。Nodoubtthisdecreaseinsizemaybelargelyattributedtolessfavourableconditionsoflife;yetanimalsroamingoverlargeparks，andfedduringseverewinters，canhardlybeconsideredasplacedunderveryunfavourableconditions。
WithSHEEPtherehasoftenbeenlong—continuedinterbreedingwithinthelimitsofthesameflock;butwhetherthenearestrelationshavebeenmatchedsofrequentlyasinthecaseofShorthorncattle，Idonotknow。TheMessrs。
BrownduringfiftyyearshaveneverinfusedfreshbloodintotheirexcellentflockofLeicesters。Since1810Mr。BarfordhasactedonthesameprinciplewiththeFoscoteflock。Heassertsthathalfacenturyofexperiencehasconvincedhimthatwhentwonearlyrelatedanimalsarequitesoundinconstitution，in—and—inbreedingdoesnotinducedegeneracy;butheaddsthathe\"doesnotpridehimselfonbreedingfromthenearestaffinities。\"InFrancetheNazflockhasbeenbredforsixtyyearswithouttheintroductionofasinglestrangeram。（17/11。ForthecaseoftheMessrs。Brownsee’Gardener’sChronicle’1855page26。FortheFoscoteflock’Gardener’sChronicle’1860
page416。FortheNazflock’Bull。delaSoc。d’Acclimat。’1860page477。）
Nevertheless，mostgreatbreedersofsheephaveprotestedagainstcloseinterbreedingprolongedfortoogreatalengthoftime。（17/12。Nathusius’Rindvieh’s。65;’YouattonSheep’page495。）Themostcelebratedofrecentbreeders，JonasWebb，keptfiveseparatefamiliestoworkon，thus\"retainingtherequisitedistanceofrelationshipbetweenthesexes\"（17/13。’Gardener’sChronicle’1861page631。）;andwhatisprobablyofgreaterimportance，theseparateflockswillhavebeenexposedtosomewhatdifferentconditions。
Althoughbytheaidofcarefulselectionthenearinterbreedingofsheepmaybelongcontinuedwithoutanymanifestevil，yetithasoftenbeenthepracticewithfarmerstocrossdistinctbreedstoobtainanimalsforthebutcher，whichplainlyshowsthatgoodofsomekindisderivedfromthispractice。WehaveexcellentevidenceonthisheadfromMr。S。Druce（17/14。
’JournalR。Agricult。Soc。’volume141853page212。），whogivesindetailthecomparativenumbersoffourpurebreedsandofacross—breedwhichcanbesupportedonthesameground，andhegivestheirproduceinfleeceandcarcase。Ahighauthority，Mr。Pusey，sumsuptheresultinmoneyvalueduringanequallengthoftime，namely（neglectingshillings），forCotswolds248
pounds，forLeicesters223pounds，forSouthdowns204pounds，forHampshireDowns264pounds，andforthecrossbred293pounds。Aformercelebratedbreeder，LordSomerville，statesthathishalf—breedsfromRyelandsandSpanishsheepwerelargeranimalsthaneitherthepureRyelandsorpureSpanishsheep。Mr。SpoonerconcludeshisexcellentEssayonCrossingbyassertingthatthereisapecuniaryadvantageinjudiciouscross—breeding，especiallywhenthemaleislargerthanthefemale。（17/15。LordSomerville’FactsonSheepandHusbandry’page6。Mr。Spoonerin’JournalofRoyalAgricult。Soc。ofEngland’volume20part2。Seealsoanexcellentpaperonthesamesubjectin’Gardener’sChronicle’1860page321byMr。CharlesHoward。）
AssomeofourBritishparksareancient，itoccurredtomethattheremusthavebeenlong—continuedcloseinterbreedingwiththefallow—deer（Cervusdama）keptinthem;butoninquiryIfindthatitisacommonpracticetoinfusenewbloodbyprocuringbucksfromotherparks。Mr。Shirley（17/16。
’SomeAccountofEnglishDeerParks’byEvelynP。Shirley1867。），whohascarefullystudiedthemanagementofdeer，admitsthatinsomeparkstherehasbeennoadmixtureofforeignbloodfromatimebeyondthememoryofman。Butheconcludes\"thatintheendtheconstantbreedingin—and—inissuretotelltothedisadvantageofthewholeherd，thoughitmaytakeaverylongtimetoproveit;moreover，whenwefind，asisveryconstantlythecase，thattheintroductionoffreshbloodhasbeenoftheverygreatestusetodeer，bothbyimprovingtheirsizeandappearance，andparticularlybybeingofserviceinremovingthetaintof’rickback，’ifnotofotherdiseases，towhichdeeraresometimessubjectwhenthebloodhasnotbeenchanged，therecan，Ithink，benodoubtbutthatajudiciouscrosswithagoodstockisofthegreatestconsequence，andisindeedessential，soonerorlater，totheprosperityofeverywell—orderedpark。\"
Mr。Meynell’sfamousfoxhoundshavebeenadduced，asshowingthatnoilleffectsfollowfromcloseinterbreeding;andSirJ。Sebrightascertainedfromhimthathefrequentlybredfromfatheranddaughter，motherandson，andsometimesevenfrombrothersandsisters。Withgreyhoundsalsotherehasbeenmuchcloseinterbreeding，butthebestbreedersagreethatitmaybecarriedtoofar。（17/17。Stonehenge’TheDog’1867pages175—188。）ButSirJ。Sebrightdeclares（17/18。’TheArtofImprovingtheBreed’etc。page13。WithrespecttoScotchdeerhoundsseeScrope’ArtofDeerStalking’pages350—353。），thatbybreedingin—and—in，bywhichhemeansmatchingbrothersandsisters，hehasactuallyseentheoffspringofstrongspanielsdegenerateintoweakanddiminutivelapdogs。TheRev。W。D。Foxhascommunicatedtomethecaseofasmalllotofbloodhounds，longkeptinthesamefamily，whichhadbecomeverybadbreeders，andnearlyallhadabonyenlargementinthetail。Asinglecrosswithadistinctstrainofbloodhoundsrestoredtheirfertility，anddroveawaythetendencytomalformationinthetail。Ihaveheardtheparticularsofanothercasewithbloodhounds，inwhichthefemalehadtobeheldtothemale。Consideringhowrapidisthenaturalincreaseofthedog，itisdifficulttounderstandthelargepriceofallhighlyimprovedbreeds，whichalmostimplieslong—continuedcloseinterbreeding，exceptonthebeliefthatthisprocesslessensfertilityandincreasesliabilitytodistemperandotherdiseases。Ahighauthority，Mr。Scrope，attributestherarityanddeteriorationinsizeoftheScotchdeerhound（thefewindividualsformerlyexistingthroughoutthecountrybeingallrelated）inlargeparttocloseinterbreeding。
Withallhighly—bredanimalsthereismoreorlessdifficultyingettingthemtoprocreatequickly，andallsuffermuchfromdelicacyofconstitution。A
greatjudgeofrabbits（17/19。’CottageGardener’1861page327。）says，\"thelong—eareddoesareoftentoohighlybredorforcedintheiryouthtobeofmuchvalueasbreeders，oftenturningoutbarrenorbadmothers。\"Theyoftendeserttheiryoung，sothatitisnecessarytohavenurse—rabbits，butIdonotpretendtoattributealltheseevilresultstocloseinterbreeding。
（17/20。Mr。Huthgives（’TheMarriageofNearKin’1875page302）fromthe’Bulletindel’Acad。R。deMed。deBelgique’（volume91866pages287，305），severalstatementsmadebyaM。Legrainwithrespecttocrossingbrotherandsisterrabbitsforfiveorsixsuccessivegenerationswithnoconsequentevilresults。Iwassomuchsurprisedatthisaccount，andatM。Legrain’sinvariablesuccessinhisexperiments，thatIwrotetoadistinguishednaturalistinBelgiumtoinquirewhetherM。Legrainwasatrustworthyobserver。Inanswer，Ihaveheardthat，asdoubtswereexpressedabouttheauthenticityoftheseexperiments，acommissionofinquirywasappointed，andthatatasucceedingmeetingoftheSociety（’Bull。del’Acad。R。deMed。deBelgique’18673rdseriestome1no。1to5），Dr。Crocqreported\"qu’iletaitmateriellementimpossiblequeM。Legrainaitfaitlesexperiencesqu’ilannonce。\"Tothispublicaccusationnosatisfactoryanswerwasmade。）
WithrespecttoPIGSthereismoreunanimityamongstbreedersontheevileffectsofcloseinterbreedingthan，perhaps，withanyotherlargeanimal。Mr。
Druce，agreatandsuccessfulbreederoftheImprovedOxfordshires（acrossedrace），writes，\"withoutachangeofboarsofadifferenttribe，butofthesamebreed，constitutioncannotbepreserved。\"Mr。FisherHobbs，theraiserofthecelebratedImprovedEssexbreed，dividedhisstockintothreeseparatefamilies，bywhichmeanshemaintainedthebreedformorethantwentyyears，\"byjudiciousselectionfromtheTHREEDISTINCTFAMILIES。\"（17/21。Sidney’seditionof’YouattonthePig’1860page30;page33quotationfromMr。Druce;
page29onLordWestern’scase。）LordWesternwasthefirstimporterofaNeapolitanboarandsow。\"Fromthispairhebredin—and—in，untilthebreedwasindangerofbecomingextinct，asureresult（asMr。Sidneyremarks）ofin—and—inbreeding。\"LordWesternthencrossedhisNeapolitanpigswiththeoldEssex，andmadethefirstgreatsteptowardstheImprovedEssexbreed。
Hereisamoreinterestingcase。Mr。J。Wright，wellknownasabreeder，crossed（17/22。’JournalofRoyalAgricult。Soc。ofEngland’1846volume7
page205。）thesameboarwiththedaughter，granddaughter，andgreat—
granddaughter，andsoonforsevengenerations。Theresultwas，thatinmanyinstancestheoffspringfailedtobreed;inotherstheyproducedfewthatlived;andofthelattermanywereidiotic，withoutsense，eventosuck，andwhenattemptingtomovecouldnotwalkstraight。Nowitdeservesespecialnotice，thatthetwolastsowsproducedbythislongcourseofinterbreedingweresenttootherboars，andtheyboreseverallittersofhealthypigs。Thebestsowinexternalappearanceproducedduringthewholesevengenerationswasoneinthelaststageofdescent;butthelitterconsistedofthisonesow。Shewouldnotbreedtohersire，yetbredatthefirsttrialtoastrangerinblood。Sothat，inMr。Wright’scase，long—continuedandextremelycloseinterbreedingdidnotaffecttheexternalformormeritoftheyoung;
butwithmanyofthemthegeneralconstitutionandmentalpowers，andespeciallythereproductivefunctions，wereseriouslyaffected。
Nathusiusgives（17/23。’UeberRindvieh’etc。s。78。Col。LeCouteur，whohasdonesomuchfortheagricultureofJersey，writestomethatfrompossessingafinebreedofpigshebredthemveryclosely，twicepairingbrothersandsisters，butnearlyalltheyounghadfitsanddiedsuddenly。）ananalogousandevenmorestrikingcase:heimportedfromEnglandapregnantsowofthelargeYorkshirebreed，andbredtheproductcloselyin—and—inforthreegenerations:theresultwasunfavourable，astheyoungwereweakinconstitution，withimpairedfertility。Oneofthelatestsows，whichheesteemedagoodanimal，produced，whenpairedwithherownuncle（whowasknowntobeproductivewithsowsofotherbreeds），alitterofsix，andasecondtimealitterofonlyfiveweakyoungpigs。Hethenpairedthissowwithaboarofasmallblackbreed，whichhehadlikewiseimportedfromEngland;thisboar，whenmatchedwithsowsofhisownbreed，producedfromseventonineyoung。Now，thesowofthelargebreed，whichwassounproductivewhenpairedwithherownuncle，yieldedtothesmallblackboar，inthefirstlittertwenty—one，andinthesecondlittereighteenyoungpigs;
sothatinoneyearsheproducedthirty—ninefineyounganimals！
Asinthecaseofseveralotheranimalsalreadymentioned，evenwhennoinjuryisperceptiblefrommoderatelycloseinterbreeding，yet，toquotethewordsofMr。Coate（whofivetimeswontheannualgoldmedaloftheSmithfieldClubShowforthebestpenofpigs），\"Crossesanswerwellforprofittothefarmer，asyougetmoreconstitutionandquickergrowth;butforme，whosellagreatnumberofpigsforbreedingpurposes，Ifinditwillnotdo，asitrequiresmanyyearstogetanythinglikepurityofbloodagain。\"（17/24。Sidneyonthe’Pig’page36。Seealsonotepage34。AlsoRichardsononthe’Pig’1847page26。）]
Almostalltheanimalsasyetmentionedaregregarious，andthemalesmustfrequentlypairwiththeirowndaughters，fortheyexpeltheyoungmalesaswellasallintruders，untilforcedbyoldageandlossofstrengthtoyieldtosomestrongermale。Itisthereforenotimprobablethatgregariousanimalsmayhavebeenrenderedlesssusceptiblethannon—socialspeciestotheevilconsequencesofcloseinterbreeding，sothattheymaybeenabledtoliveinherdswithoutinjurytotheiroffspring。Unfortunatelywedonotknowwhetherananimallikethecat，whichisnotgregarious，wouldsufferfromcloseinterbreedinginagreaterdegreethanourotherdomesticatedanimals。Butthepigisnot，asfarasIcandiscover，strictlygregarious，andwehaveseenthatitappearseminentlyliabletotheevileffectsofcloseinterbreeding。
Mr。Huth，inthecaseofthepig，attributes（page285）theseeffectstotheirhavingbeen\"cultivatedmostfortheirfat，\"ortotheselectedindividualshavinghadaweakconstitution;butwemustrememberthatitisgreatbreederswhohavebroughtforwardtheabovecases，andwhoarefarmorefamiliarthanordinarymencanbe，withthecauseswhicharelikelytointerferewiththefertilityoftheiranimals。
Theeffectsofcloseinterbreedinginthecaseofmanisadifficultsubject，onwhichIwillsaybutlittle。Ithasbeendiscussedbyvariousauthorsundermanypointsofview。（17/25。Dr。Dallyhaspublishedanexcellentarticle（translatedinthe’Anthropolog。Review’May1864page65），criticisingallwriterswhohavemaintainedthatevilfollowsfromconsanguineousmarriages。
Nodoubtonthissideofthequestionmanyadvocateshaveinjuredtheircausebyinaccuracies:thusithasbeenstated（Devay’DuDangerdesMariages’etc。
1862page141）thatthemarriagesofcousinshavebeenprohibitedbythelegislatureofOhio;butIhavebeenassured，inanswertoinquiriesmadeintheUnitedStates，thatthisstatementisamerefable。）Mr。Tylor（17/26。Seehisinterestingworkonthe’EarlyHistoryofMan’1865chapter10。）hasshownthatwithwidelydifferentracesinthemostdistantquartersoftheworld，marriagesbetweenrelations——evenbetweendistantrelations——havebeenstrictlyprohibited。Thereare，however，manyexceptionstotherule，whicharefullygivenbyMr。Huth（17/27。’TheMarriageofNearKin’1875。TheevidencegivenbyMr。Huthwould，Ithink，havebeenevenmorevaluablethanitisonthisandsomeotherpoints，ifhehadreferredsolelytotheworksofmenwhohadlongresidedineachcountryreferredto，andwhoshowedthattheypossessedjudgmentandcaution。SeealsoMr。W。Adam’OnConsanguinityinMarriage’inthe’FortnightlyReview’1865page710。AlsoHofacker’UeberdieEigenschaften’etc。1828。）Itisacuriousproblemhowtheseprohibitionsaroseduringearlyandbarbaroustimes。Mr。Tylorisinclinedtoattributethemtotheevileffectsofconsanguineousmarriageshavingbeenobserved;andheingeniouslyattemptstoexplainsomeapparentanomaliesintheprohibitionnotextendingequallytotherelationsonthemaleandfemaleside。Headmits，however，thatothercauses，suchastheextensionoffriendlyalliances，mayhavecomeintoplay。Mr。W。Adam，ontheotherhand，concludesthatrelatedmarriagesareprohibitedandviewedwithrepugnance，fromtheconfusionwhichwouldthusariseinthedescentofproperty，andfromotherstillmorereconditereasons。ButIcannotaccepttheseviews，seeingthatincestisheldinabhorrencebysavagessuchasthoseofAustraliaandSouthAmerica（17/28。
SirG。Grey’JournalofExpeditionsintoAustralia’volume2page243;andDobrizhoffer’OntheAbiponesofSouthAmerica。’），whohavenopropertytobequeath，orfinemoralfeelingstoconfuse，andwhoarenotlikelytoreflectondistantevilstotheirprogeny。AccordingtoMr。Huththefeelingistheindirectresultofexogamy，inasmuchaswhenthispracticeceasedinanytribeanditbecameendogamous，sothatmarriageswerestrictlyconfinedtothesametribe，itisnotunlikelythatavestigeoftheformerpracticewouldstillberetained，sothatclosely—relatedmarriageswouldbeprohibited。WithrespecttoexogamyitselfMr。MacLennanbelievesthatitarosefromascarcityofwomen，owingtofemaleinfanticide，aidedperhapsbyothercauses。
IthasbeenclearlyshownbyMr。Huththatthereisnoinstinctivefeelinginmanagainstincestanymorethaningregariousanimals。Weknowalsohowreadilyanyprejudiceorfeelingmayrisetoabhorrence，asshownbyHindusinregardtoobjectscausingdefilement。Althoughthereseemstobenostronginheritedfeelinginmankindagainstincest，itseemspossiblethatmenduringprimevaltimesmayhavebeenmoreexcitedbystrangefemalesthanbythosewithwhomtheyhabituallylived;inthesamemannerasaccordingtoMr。
Cupples（17/29。’DescentofMan’2nd。editpage524。），maledeerhoundsareinclinedtowardsstrangefemales，whilethefemalespreferdogswithwhomtheyhaveassociated。Ifanysuchfeelingformerlyexistedinman，thiswouldhaveledtoapreferenceformarriagesbeyondthenearestkin，andmighthavebeenstrengthenedbytheoffspringofsuchmarriagessurvivingingreaternumbers，asanalogywouldleadustobelievewouldhaveoccurred。
Whetherconsanguineousmarriages，suchasarepermittedincivilisednations，andwhichwouldnotbeconsideredascloseinterbreedinginthecaseofourdomesticatedanimals，causeanyinjurywillneverbeknownwithcertaintyuntilacensusistakenwiththisobjectinview。Myson，GeorgeDarwin，hasdonewhatispossibleatpresentbyastatisticalinvestigation（17/30。
’JournalofStatisticalSoc。’June1875page153;and’FortnightlyReview’
June1875。），andhehascometotheconclusion，fromhisownresearchesandthoseofDr。Mitchell，thattheevidenceastoanyevilthuscausedisconflicting，butonthewholepointstotheevilbeingverysmall。