Hence, it has come, that when we compare the now living productions of the temperate regions of the New and Old Worlds, we find very few identical species (though Asa Gray has lately shown that more plants are identical than was formerly supposed), but we find in every great class many forms, which some naturalists rank as geographical races, and others as distinct species; and a host of closely allied or representative forms which are ranked by all naturalists as specifically distinct.
Hemendixek dator, mundu zahar eta berriko klima epelean egun bizi diren ekoizkinak konparatzen ditugunean, espezie berdin-berdin gutxi aurkitzea (nahiz eta Assa Grayk oraintsu frogatu duen lehen uste zen baino landare gehiago direla berdin-berdinak) eta klase nagusi guztietan, ordea, naturalista askok arraza geografikotzat eta beste batzuek espezie ezberdintzat sailkatzen dituzten forma asko aurkitzea.