These causes, taken conjointly, will to a large extent explain why-though we do find many links-we do not find interminable varieties, connecting together all extinct and existing forms by the finest graduated steps.
Aipaturiko kausok, oro har, azalduko dute zati handi batean zergatik-katenbegi asko aurkitu arren-ez dugun aurkitzen amaigabeko aldaki andanarik, mailaz mailako urrats mehez forma bizi eta iraungi guztiak elkarlotzen.