It is universally admitted, that in most cases the area inhabited by a species is continuous; and that when a plant or animal inhabits two points so distant from each other, or with an interval of such a nature, that the space could not have been easily passed over by migration, the fact is given as something remarkable and exceptional.
Unibertsalki onartua da, kasurik gehienetan, espezie bat bizi den herrialdea etengabea dela, eta, landare edo animalia bat bi toki elkarretatik hain urrunetan, edo toki bien artean, migrari abiatuz nekez gainditzeko moduko bitartea izanik bizi denean, egitate hau nabarmen eta salbuespenekotzat aipatzen da.