that varieties have at first been local; and lastly, although each species must have passed through numerous transitional stages, it is probable that the periods, during which each underwent modification, though many and long as measured by years, have been short in comparison with the periods during which each remained in an unchanged condition.
eta, azkenez, nahiz eta espezie bakoitzak iragaitzazko egoera askotatik pasa behar izan duen, aldakuntzak izan dituen aldiak, asko eta urtez neurturik luzeak izan arren, aldagabe egon diren aldien aldean laburrak izan direla ziurrenik.