and in these intervals there may have been much slow extermination. Moreover, when, by sudden immigration or by unusually rapid development, many species of a new group have taken possession of an area, many of the older species will have been exterminated in a correspondingly rapid manner; and the forms which thus yield their places will commonly be allied, for they will partake of the same inferiority in common.
Gainera, bat-bateko inmigrazioa edo ohi ez bezalako garapen azkarra bide, talde berri bateko espezie asko herrialde batez jabetzean, espezie zaharretariko askok suntsituak izan beharko zuten berriak sartu ahala; eta, era horretan, beren lekuak berriei uzten dizkien formak ahaideak izanen dira eskuarki, gutxiagotasun bera izanen dutelako guztiak.