The Foundations of the Origin of Species: Two Essays Written in 1842 and 1844

abortive organs acquired adapted admit affinity allied Alpine Alpine plants America analogous appear Archipelago become believe birds breed cattle cause changes chapter characters climate common common descent continent corresponding crossing Crustaceans Darwin degree descended difficulty discussion distinct distribution dogs domestic races doubt effect embryo Europe evidence existing external conditions extinct facts Falkland Islands favourable fertile floras forms fossil full-grown Galapagos Galapagos Archipelago genera genus geological geologists germinal vesicle gradation groups habits hereditary hybrids illegible individuals inhabitants inherited instance instincts intermediate islands land larvæ less Letters Lyell main divisions mammæ mammifers Marsupial means mountains naturalists nature Note in original occurs offspring Origin of Species Pachydermata parent passage peculiar period plants preserved probably produced quadrupeds remarked reproductive resemblance Rodents seeds selection sheep similar slight sterility structure suppose tend tendency terrestrial animals theory Tierra del Fuego tion unity of type variation varieties vary wild young