The main cause, however, of innumerable intermediate links not now occurring everywhere throughout nature depends, on the very process of natural selection, through which new varieties continually take the places of and supplant their parent-forms.
Hala ere, naturan nonahi bitarteko lokarri ugaririk ez agertzearen kausa nagusia, hautespen naturalaren prozesuaren beraren mende dago, harexen bidez hartzen baitute aldaki berriek guraso-formen lekua eta haiek ordezkatzen.