MyworkontheCirripediapossesses，Ithink，considerablevalue，asbesidesdescribingseveralnewandremarkableforms，Imadeoutthehomologiesofthevariousparts——Idiscoveredthecementingapparatus，thoughIblundereddreadfullyaboutthecementglands——andlastlyIprovedtheexistenceincertaingeneraofminutemalescomplementaltoandparasiticonthehermaphrodites。Thislatterdiscoveryhasatlastbeenfullyconfirmed;thoughatonetimeaGermanwriterwaspleasedtoattributethewholeaccounttomyfertileimagination。TheCirripedesformahighlyvaryinganddifficultgroupofspeciestoclass;andmyworkwasofconsiderableusetome，whenIhadtodiscussinthe’OriginofSpecies’
theprinciplesofanaturalclassification。Nevertheless，Idoubtwhethertheworkwasworththeconsumptionofsomuchtime。
>FromSeptember1854Idevotedmywholetimetoarrangingmyhugepileofnotes，toobserving，andtoexperimentinginrelationtothetransmutationofspecies。Duringthevoyageofthe\"Beagle\"IhadbeendeeplyimpressedbydiscoveringinthePampeanformationgreatfossilanimalscoveredwitharmourlikethatontheexistingarmadillos;secondly，bythemannerinwhichcloselyalliedanimalsreplaceoneanotherinproceedingsouthwardsovertheContinent;andthirdly，bytheSouthAmericancharacterofmostoftheproductionsoftheGalapagosarchipelago，andmoreespeciallybythemannerinwhichtheydifferslightlyoneachislandofthegroup;noneoftheislandsappearingtobeveryancientinageologicalsense。
Itwasevidentthatsuchfactsasthese，aswellasmanyothers，couldonlybeexplainedonthesuppositionthatspeciesgraduallybecomemodified;andthesubjecthauntedme。Butitwasequallyevidentthatneithertheactionofthesurroundingconditions，northewilloftheorganisms（especiallyinthecaseofplants）couldaccountfortheinnumerablecasesinwhichorganismsofeverykindarebeautifullyadaptedtotheirhabitsoflife——
forinstance，awoodpeckeroratree—frogtoclimbtrees，oraseedfordispersalbyhooksorplumes。Ihadalwaysbeenmuchstruckbysuchadaptations，anduntilthesecouldbeexplaineditseemedtomealmostuselesstoendeavourtoprovebyindirectevidencethatspecieshavebeenmodified。