in travelling from north to south over a continent, we generally meet at successive intervals with closely allied or representative species, evidently filling nearly the same place in the natural economy of the land.
kontinente bat iparretik hegora zeharkatzean, espezie oso hurbil edo errepresentagarriekin egiten dugu topo hurrenez hurreneko tarteetan, herrialdeko natur ekonomian ia-ia leku bera betetzen nabariki.