A number of species, however, keeping in a body might remain for a long period unchanged, whilst within the same period, several of these species, by migrating into new countries and coming into competition with foreign associates, might become modified;
Espezie batzuek, hala ere, multzo batean bildurik, aldakuntzarik izan gabe iraun zezaketen luzaro, horietako beste espezie batzuk, ostera, aldi berorretan, beste herrialde batzuetara migratu eta forma atzerritarrekin lehian sartuz, eraldatuak gertatu diren artean;