Indomitablepatience，thefinestpowersofdiscrimination，andsoundjudgmentmustbeexercisedduringmanyyears。Aclearlypredeterminedobjectmustbekeptsteadilyinview。Fewmenareendowedwithallthesequalities，especiallywiththatofdiscriminatingveryslightdifferences;judgmentcanbeacquiredonlybylongexperience;butifanyofthesequalitiesbewanting，thelabourofalifemaybethrownaway。Ihavebeenastonishedwhencelebratedbreeders，whoseskillandjudgmenthavebeenprovedbytheirsuccessatexhibitions，haveshownmetheiranimals，whichappearedallalike，andhaveassignedtheirreasonsformatchingthisandthatindividual。TheimportanceofthegreatprincipleofSelectionmainlyliesinthispowerofselectingscarcelyappreciabledifferences，whichneverthelessarefoundtobetransmissible，andwhichcanbeaccumulateduntiltheresultismademanifesttotheeyesofeverybeholder。
Theprincipleofselectionmaybeconvenientlydividedintothreekinds。
METHODICALSELECTIONisthatwhichguidesamanwhosystematicallyendeavourstomodifyabreedaccordingtosomepredeterminedstandard。UNCONSCIOUS
SELECTIONisthatwhichfollowsfrommennaturallypreservingthemostvaluedanddestroyingthelessvaluedindividuals，withoutanythoughtofalteringthebreed;andundoubtedlythisprocessslowlyworksgreatchanges。
Unconsciousselectiongraduatesintomethodical，andonlyextremecasescanbedistinctlyseparated;forhewhopreservesausefulorperfectanimalwillgenerallybreedfromitwiththehopeofgettingoffspringofthesamecharacter;butaslongashehasnotapredeterminedpurposetoimprovethebreed，hemaybesaidtobeselectingunconsciously。（20/1。Theterm"unconsciousselection"hasbeenobjectedtoasacontradiction;butseesomeexcellentobservationsonthisheadbyProf。Huxley（’Nat。Hist。Review’
October1864page578）whoremarksthatwhenthewindheapsupsand—dunesitsiftsandUNCONSCIOUSLYSELECTSfromthegravelonthebeachgrainsofsandofequalsize。）Lastly，wehaveNATURALSELECTION，whichimpliesthattheindividualswhicharebestfittedforthecomplex，andinthecourseofageschangingconditionstowhichtheyareexposed，generallysurviveandprocreatetheirkind。Withdomesticproductions，naturalselectioncomestoacertainextentintoaction，independentlyof，andeveninoppositionto，thewillofman。
METHODICALSELECTION。
WhatmanhaseffectedwithinrecenttimesinEnglandbymethodicalselectionisclearlyshownbyourexhibitionsofimprovedquadrupedsandfancybirds。
Withrespecttocattle，sheep，andpigs，weowetheirgreatimprovementtoalongseriesofwell—knownnames——Bakewell，Coiling，Ellman，Bates，JonasWebb，LordsLeicesterandWestern，FisherHobbs，andothers。Agriculturalwritersareunanimousonthepowerofselection:anynumberofstatementstothiseffectcouldbequoted;afewwillsuffice。Youatt，asagaciousandexperiencedobserver，writes（20/2。’OnSheep’1838page60。）theprincipleofselectionis"thatwhichenablestheagriculturist，notonlytomodifythecharacterofhisflock，buttochangeitaltogether。"AgreatbreederofShorthorns（20/3。Mr。J。WrightonShorthornCattlein’JournalofRoyalAgricult。Soc。’volume7pages208，209。）says，"IntheanatomyoftheshouldermodernbreedershavemadegreatimprovementontheKettonshorthornsbycorrectingthedefectintheknuckleorshoulder—joint，andbylayingthetopoftheshouldermoresnuglyinthecrop，andtherebyfillingupthehollowbehindit……Theeyehasitsfashionatdifferentperiods:atonetimetheeyehighandoutstandingfromthehead，andatanothertimethesleepyeyesunkintothehead;buttheseextremeshavemergedintothemediumofafull，clearandprominenteyewithaplacidlook。"
Again，hearwhatanexcellentjudgeofpigs（20/4。H。D。Richardson’OnPigs’
1847page44。）says:"Thelegsshouldbenolongerthanjusttopreventtheanimal’sbellyfromtrailingontheground。Thelegistheleastprofitableportionofthehog，andwethereforerequirenomoreofitthanisabsolutelynecessaryforthesupportoftherest。"Letanyonecomparethewild—boarwithanyimprovedbreed，andhewillseehoweffectuallythelegshavebeenshortened。
Fewpersons，exceptbreeders，areawareofthesystematiccaretakeninselectinganimals，andofthenecessityofhavingaclearandalmostpropheticvisionintofuturity。LordSpencer’sskillandjudgmentwerewellknown;andhewrites（20/5。’JournalofRoyalAgricult。Soc。’volume1page24。），"Itisthereforeverydesirable，beforeanymancommencestobreedeithercattleorsheep，thatheshouldmakeuphismindtotheshapeandqualitieshewishestoobtain，andsteadilypursuethisobject。"LordSomerville，inspeakingofthemarvellousimprovementoftheNewLeicestersheep，effectedbyBakewellandhissuccessors，says，"Itwouldseemasiftheyhadfirstdrawnaperfectform，andthengivenitlife。"Youatt（20/6。’OnSheep’pages520，319。）urgesthenecessityofannuallydraftingeachflock，asmanyanimalswillcertainlydegenerate"fromthestandardofexcellencewhichthebreederhasestablishedinhisownmind。"Evenwithabirdofsuchlittleimportanceasthecanary，longago（1780—1790）ruleswereestablished，andastandardofperfectionwasfixedaccordingtowhichtheLondonfancierstriedtobreedtheseveralsub—
varieties。（20/7。Loudon’s’Mag。ofNat。Hist。’volume81835page618。）A
greatwinnerofprizesatthePigeon—shows（20/8。’AtreatiseontheArtofBreedingtheAlmondTumbler’1851page9。），indescribingtheshort—facedAlmondTumbler，says，"Therearemanyfirst—ratefancierswhoareparticularlypartialtowhatiscalledthegoldfinch—beak，whichisverybeautiful;otherssay，takeafull—sizeroundcherrythentakeabarleycorn，andjudiciouslyplacingandthrustingitintothecherry，formasitwereyourbeak;andthatisnotall，foritwillformagoodheadandbeak，provided，asIsaidbefore，itisjudiciouslydone;otherstakeanoat;butasIthinkthegoldfinch—beakthehandsomest，Iwouldadvisetheinexperiencedfanciertogettheheadofagoldfinch，andkeepitbyhimforhisobservation。"Wonderfullydifferentasarethebeaksoftherockpigeonandgoldfinch，theendhasundoubtedlybeennearlygained，asfarasexternalshapeandproportionsareconcerned。
Notonlyshouldouranimalsbeexaminedwiththegreatestcarewhilstalive，but，asAndersonremarks（20/9。’RecreationsinAgriculture’volume2page409。）theircarcasesshouldbescrutinised，"soastobreedfromthedescendantsofsuchonlyas，inthelanguageofthebutcher，cutupwell。"The"grainofthemeat"incattle，anditsbeingwellmarbledwithfat（20/10。
’YouattonCattle’pages191，227。），andthegreaterorlessaccumulationoffatintheabdomenofoursheep，havebeenattendedtowithsuccess。Sowithpoultry，awriter（20/11。Ferguson’PrizePoultry’1854page208。），speakingofCochin—Chinafowls，whicharesaidtodiffermuchinthequalityoftheirflesh，says，"thebestmodeistopurchasetwoyoungbrother—cocks，kill，dress，andserveupone;ifhebeindifferent，similarlydisposeoftheother，andtryagain;if，however，hebefineandwell—flavoured，hisbrotherwillnotbeamissforbreedingpurposesforthetable。"
Thegreatprincipleofthedivisionoflabourhasbeenbroughttobearonselection。Incertaindistricts（20/12。Wilsonin’Transact。HighlandAgricult。Soc。’quotedin’Gardener’sChronicle’1844page29。）"thebreedingofbullsisconfinedtoaverylimitednumberofpersons，whobydevotingtheirwholeattentiontothisdepartment，areablefromyeartoyeartofurnishaclassofbullswhicharesteadilyimprovingthegeneralbreedofthedistrict。"Therearingandlettingofchoiceramshaslongbeen，asiswellknown，achiefsourceofprofittoseveraleminentbreeders。InpartsofGermanythisprincipleiscarriedwithmerinosheeptoanextremepoint。
（20/13。Simmondsquotedin’Gardener’sChronicle’1855page637。Andforthesecondquotationsee’YouattonSheep’page171。）So"importantistheproperselectionofbreedinganimalsconsidered，thatthebestflock—mastersdonottrusttotheirownjudgmentortothatoftheirshepherds，butemploypersonscalled’sheep—classifiers’whomakeittheirspecialbusinesstoattendtothispartofthemanagementofseveralflocks，andthustopreserve，orifpossibletoimprove，thebestqualitiesofbothparentsinthelambs。"InSaxony，"whenthelambsareweaned，eachinhisturnisplaceduponatablethathiswoolandformmaybeminutelyobserved。Thefinestareselectedforbreedingandreceiveafirstmark。Whentheyareoneyearold，andpriortoshearingthem，anothercloseexaminationofthosepreviouslymarkedtakesplace:thoseinwhichnodefectcanbefoundreceiveasecondmark，andtherestarecondemned。Afewmonthsafterwardsathirdandlastscrutinyismade;
theprimeramsandewesreceiveathirdandfinalmark，buttheslightestblemishissufficienttocausetherejectionoftheanimal。"Thesesheeparebredandvaluedalmostexclusivelyforthefinenessoftheirwool;andtheresultcorrespondswiththelabourbestowedontheirselection。Instrumentshavebeeninventedtomeasureaccuratelythethicknessofthefibres;and"anAustrianfleecehasbeenproducedofwhichtwelvehairsequalledinthicknessonefromaLeicestersheep。"
Throughouttheworld，whereversilkisproduced，thegreatestcareisbestowedonselectingthecocoonsfromwhichthemothsforbreedingaretobereared。A
carefulcultivator（20/14。Robinet’VersaSoie’1848page271。）likewiseexaminesthemothsthemselves，anddestroysthosethatarenotperfect。ButwhatmoreimmediatelyconcernsusisthatcertainfamiliesinFrancedevotethemselvestoraisingeggsforsale。（20/15。Quatrefages’LesMaladiesduVeraSoie’1859page101。）InChina，nearShanghai，theinhabitantsoftwosmalldistrictshavetheprivilegeofraisingeggsforthewholesurroundingcountry，andthattheymaygiveuptheirwholetimetothisbusiness，theyareinterdictedbylawfromproducingsilk。（20/16。M。Simonin’Bull。delaSoc。
d’Acclimat。’tome91862page221。）
Thecarewhichsuccessfulbreederstakeinmatchingtheirbirdsissurprising。
SirJohnSebright，whosefameisperpetuatedbythe"SebrightBantam，"usedtospend"twoandthreedaysinexamining，consulting，anddisputingwithafriendwhichwerethebestoffiveorsixbirds。"（20/17。’ThePoultryChronicle’volume11854page607。）Mr。Bult，whosepouter—pigeonswonsomanyprizes，andwereexportedtoNorthAmericaunderthechargeofamansentonpurpose，toldmethathealwaysdeliberatedforseveraldaysbeforehematchedeachpair。Hencewecanunderstandtheadviceofaneminentfancier，whowrites（20/18。J。M。Eaton’ATreatiseonFancyPigeons’1852page14and’A
TreatiseontheAlmondTumbler’1851page11。）"Iwouldhereparticularlyguardyouagainsthavingtoogreatavarietyofpigeons，otherwiseyouwillknowalittleofall，butnothingaboutoneasitoughttobeknown。"
Apparentlyittranscendsthepowerofthehumanintellecttobreedallkinds:
"itispossiblethattheremaybeafewfanciersthathaveagoodgeneralknowledgeoffancypigeons;buttherearemanymorewholabourunderthedelusionofsupposingtheyknowwhattheydonot。"Theexcellenceofonesub—
variety，theAlmondTumbler，liesintheplumage，carriage，head，beak，andeye;butitistoopresumptuousinthebeginnertotryforallthesepoints。
Thegreatjudgeabovequotedsays，"Therearesomeyoungfancierswhoareover—covetous，whogoforalltheabovefivepropertiesatonce;theyhavetheirrewardbygettingnothing。"Wethusseethatbreedingevenfancypigeonsisnosimpleart:wemaysmileatthesolemnityoftheseprecepts，buthewholaughswillwinnoprizes。
Whatmethodicalselectionhaseffectedforouranimalsissufficientlyproved，asalreadyremarked，byourExhibitions。Sogreatlywerethesheepbelongingtosomeoftheearlierbreeders，suchasBakewellandLordWestern，changed，thatmanypersonscouldnotbepersuadedthattheyhadnotbeencrossed。Ourpigs，asMr。Corringhamremarks（20/19。’JournalRoyalAgriculturalSoc。’
volume6page22。）duringthelasttwentyyearshaveundergone，throughrigorousselectiontogetherwithcrossing，acompletemetamorphosis。ThefirstexhibitionforpoultrywasheldintheZoologicalGardensin1845;andtheimprovementeffectedsincethattimehasbeengreat。AsMr。Bailey，thegreatjudge，remarkedtome，itwasformerlyorderedthatthecomboftheSpanishcockshouldbeupright，andinfourorfiveyearsallgoodbirdshaduprightcombs;itwasorderedthatthePolishcockshouldhavenocomborwattles，andnowabirdthusfurnishedwouldbeatoncedisqualified;beardswereordered，andoutoffifty—sevenpenslately（1860）exhibitedattheCrystalPalace，allhadbeards。Soithasbeeninmanyothercases。Butinallcasesthejudgesorderonlywhatisoccasionallyproducedandwhatcanbeimprovedandrenderedconstantbyselection。Thesteadyincreaseinweightduringthelastfewyearsinourfowls，turkeys，ducks，andgeeseisnotorious;"six—poundducksarenowcommon，whereasfourpoundswasformerlytheaverage。"Asthetimerequiredtomakeachangehasnotoftenbeenrecorded，itmaybeworthmentioningthatittookMr。Wickingthirteenyearstoputacleanwhiteheadonanalmondtumbler’sbody，"atriumph，"saysanotherfancier，"ofwhichhemaybejustlyproud。"（20/20。’PoultryChronicle’volume21855page596。）
Mr。Tollet，ofBetleyHall，selectedcows，andespeciallybulls，descendedfromgoodmilkers，forthesolepurposeofimprovinghiscattlefortheproductionofcheese;hesteadilytestedthemilkwiththelactometer，andineightyearsheincreased，asIwasinformedbyhim，theproductinproportionoffourtothree。Hereisacuriouscase（20/21。Isid。GeoffroySt。—Hilaire’Hist。Nat。Gen。’tome3page254。）ofsteadybutslowprogress，withtheendnotasyetfullyattained:in1784araceofsilkwormswasintroducedintoFrance，inwhichonehundredinthethousandfailedtoproducewhitecocoons;
butnowaftercarefulselectionduringsixty—fivegenerations，theproportionofyellowcocoonshasbeenreducedtothirty—fiveinthethousand。
Withplantsselectionhasbeenfollowedwiththesamegoodresultaswithanimals。Buttheprocessissimpler，forplantsinthegreatmajorityofcasesbearbothsexes。Nevertheless，withmostkindsitisnecessarytotakeasmuchcaretopreventcrossesaswithanimalsorunisexualplants;butwithsomeplants，suchaspeas，thiscareisnotnecessary。Withallimprovedplants，exceptingofcoursethosewhicharepropagatedbybuds，cuttings，etc。，itisalmostindispensabletoexaminetheseedlingsanddestroythosewhichdepartfromthepropertype。Thisiscalled"roguing，"andis，infact，aformofselection，liketherejectionofinferioranimals。Experiencedhorticulturistsandagriculturistsincessantlyurgeeveryonetopreservethefinestplantsfortheproductionofseed。
Althoughplantsoftenpresentmuchmoreconspicuousvariationsthananimals，yettheclosestattentionisgenerallyrequisitetodetecteachslightandfavourablechange。Mr。Mastersrelates（20/22。’Gardener’sChronicle’1850
page198。）how"manyapatienthourwasdevoted，"whilsthewasyoung，tothedetectionofdifferencesinpeasintendedforseed。Mr。Barnet（20/23。
’Transact。Hort。Soc。’volume6page152。）remarksthattheoldscarletAmericanstrawberrywascultivatedformorethanacenturywithoutproducingasinglevariety;andanotherwriterobserveshowsingularitwasthatwhengardenersfirstbegantoattendtothisfruititbegantovary;thetruthnodoubtbeingthatithadalwaysvaried，butthat，untilslightvariationswereselectedandpropagatedbyseed，noconspicuousresultwasobtained。Thefinestshadesofdifferenceinwheathavebeendiscriminatedandselectedwithalmostasmuchcareas，inthecaseofthehigheranimals，forinstancebyCol。LeCouteurandmoreespeciallybyMajorHallett。
Itmaybeworthwhiletogiveafewexamplesofmethodicalselectionwithplants;butinfactthegreatimprovementofallourancientlycul...完整阅读请扫描二维码下载丁香书院APP免费看：