Withtheincreasedordiminishedlengthofthebeakthelengthoftheslitformingtheexternalorificeofthenostrilsvaries，butnotindueproportion，for，takingtherock—pigeonasthestandard，theorificeinaShort—facedTumblerwasnotshortenedindueproportionwithitsveryshortbeak。Ontheotherhand（andthiscouldnothavebeenanticipated），theorificeinthreeEnglishCarriers，intheBagadottenCarrier，andinaRunt（pigeoncygne），waslongerbyabovethetenthofaninchthanwouldfollowfromthelengthofthebeakproportionallywiththatoftherock—pigeon。InoneCarriertheorificeofthenostrilswasthriceaslongasintherock—
pigeon，thoughinbodyandlengthofbeakthisbirdwasnotnearlydoublethesizeoftherock—pigeon。Thisgreatlyincreasedlengthoftheorificeofthenostrilsseemstostandpartlyincorrelationwiththeenlargementofthewattledskinontheuppermandibleandoverthenostrils;andthisisacharacterwhichisselectedbyfanciers。Soagain，thebroad，naked，andwattledskinroundtheeyesofCarriersandBarbsisaselectedcharacter;andinobviouscorrelationwiththis，theeyelids，measuredlongitudinally，areproportionallymorethandoublethelengthofthoseoftherock—pigeon。
Thegreatdifference（seefigure27）inthecurvatureofthelowerjawintherock—pigeon，theTumbler，andBagadottenCarrier，standsinobviousrelationtothecurvatureoftheupperjaw，andmoreespeciallytotheangleformedbythemaxillo—jugalarchwiththepremaxillarybones。ButinCarriers，Runts，andBarbsthesingularreflexionoftheuppermarginofthemiddlepartofthelowerjaw（seefigure25）isnotstrictlycorrelatedwiththewidthordivergence（asmaybeclearlyseeninfigure26）ofthepremaxillarybones，butwiththebreadthofthehornyandsoftpartsoftheuppermandible，whicharealwaysoverlappedbytheedgesofthelowermandible。
InPouters，theelongationofthebodyisaselectedcharacter，andtheribs，aswehaveseen，havegenerallybecomeverybroad，withtheseventhpairfurnishedwithprocesses;thesacralandcaudalvertebraehavebeenaugmentedinnumber;thesternumhaslikewiseincreasedinlength（butnotinthedepthofthecrest）by。4ofaninchmorethanwouldfollowfromthegreaterbulkofthebodyincomparisonwiththatoftherock—pigeon。InFantails，thelengthandnumberofthecaudalvertebraehaveincreased。
Hence，duringthegradualprogressofvariationandselection，theinternalbonyframeworkandtheexternalshapeofthebodyhavebeen，toacertainextent，modifiedinacorrelatedmanner。