Undoubtedly there is one most important point of difference between varieties and species, namely, that the amount of difference between varieties, when compared with each other or with their parent-species, is much less than that between the species of the same genus.
Dudarik ez, bada ezberdintasun bat aldakien eta espezieen artean, eta hauxe da, hots, aldakien artean dagoen diferentzia, elkarren artean edo guraso-espeziearekin konparatzen direnean, genero bereko espezieen artekoa baino askoz txikiagoa dela.