Ofterrestrialmammals，thereisonlyonewhichmustbeconsideredasindigenous，namely，amouseMusGalapagoensis，andthisisconfined，asfarasIcouldascertain，toChathamIsland，themosteasterlyislandofthegroup。Itbelongs，asIaminformedbyMr。Waterhouse，toadivisionofthefamilyofmicecharacteristicofAmerica。AtJamesIsland，thereisaratsufficientlydistinctfromthecommonkindtohavebeennamedanddescribedbyMr。Waterhouse；butasitbelongstotheold-worlddivisionofthefamily，andasthisislandhasbeenfrequentedbyshipsforthelasthundredandfiftyyears，Icanhardlydoubtthatthisratismerelyavarietyproducedbythenewandpeculiarclimate，food，andsoil，towhichithasbeensubjected。Althoughnoonehasarighttospeculatewithoutdistinctfacts，yetevenwithrespecttotheChathamIslandmouse，itshouldbeborneinmind，thatitmaypossiblybeanAmericanspeciesimportedhere；forIhaveseen，inamostunfrequentedpartofthePampas，anativemouselivingintheroofofanewlybuilthovel，andthereforeitstransportationinavesselisnotimprobable：analogousfactshavebeenobservedbyDr。
RichardsoninNorthAmerica。
Ofland-birdsIobtainedtwenty-sixkinds，allpeculiartothegroupandfoundnowhereelse，withtheexceptionofonelark-likefinchfromNorthAmericaDolichonyxoryzivorus，whichrangesonthatcontinentasfarnorthas54degs。，andgenerallyfrequentsmarshes。Theothertwenty-fivebirdsconsist，firstly，ofahawk，curiouslyintermediateinstructurebetweenabuzzardandtheAmericangroupofcarrion-feedingPolybori；andwiththeselatterbirdsitagreesmostcloselyineveryhabitandeventoneofvoice。Secondly，therearetwoowls，representingtheshort-earedandwhitebarn-owlsofEurope。Thirdly，awren，threetyrant-flycatcherstwoofthemspeciesofPyrocephalus，oneorbothofwhichwouldberankedbysomeornithologistsasonlyvarieties，andadove——allanalogousto，butdistinctfrom，Americanspecies。Fourthly，aswallow，whichthoughdifferingfromthePrognepurpureaofbothAmericas，onlyinbeingratherdullercolored，smaller，andslenderer，isconsideredbyMr。Gouldasspecificallydistinct。Fifthly，therearethreespeciesofmockingthrush——aformhighlycharacteristicofAmerica。Theremainingland-birdsformamostsingulargroupoffinches，relatedtoeachotherinthestructureoftheirbeaks，shorttails，formofbodyandplumage：therearethirteenspecies，whichMr。Gouldhasdividedintofoursubgroups。Allthesespeciesarepeculiartothisarchipelago；andsoisthewholegroup，withtheexceptionofonespeciesofthesub-groupCactornis，latelybroughtfromBowIsland，intheLowArchipelago。OfCactornis，thetwospeciesmaybeoftenseenclimbingabouttheflowersofthegreatcactus-trees；butalltheotherspeciesofthisgroupoffinches，mingledtogetherinflocks，feedonthedryandsterilegroundofthelowerdistricts。Themalesofall，orcertainlyofthegreaternumber，arejetblack；andthefemaleswithperhapsoneortwoexceptionsarebrown。ThemostcuriousfactistheperfectgradationinthesizeofthebeaksinthedifferentspeciesofGeospiza，fromoneaslargeasthatofahawfinchtothatofachaffinch，andifMr。Gouldisrightinincludinghissub-group，Certhidea，inthemaingroupeventothatofawarbler。ThelargestbeakinthegenusGeospizaisshowninFig。1，andthesmallestinFig。3；butinsteadoftherebeingonlyoneintermediatespecies，withabeakofthesizeshowninFig。2，therearenolessthansixspecieswithinsensiblygraduatedbeaks。Thebeakofthesub-groupCerthidea，isshowninFig。4。ThebeakofCactornisis[picture]
1。Geospizamagnirostris。2。Geospizafortis。3。Geospizaparvula。4。
Certhideaolivasea。
......购买会员看全站小说，或者下载APP免费观看所有作品 点击立即下载，搜索"THE VOYAGE OF THE BEAGLE",免费读到尾