Thirdly, when two or more varieties have been formed in different portions of a strictly continuous area, intermediate varieties will, it is probable, at first have been formed in the intermediate zones, but they will generally have had a short duration.
Izan ere, bitarteko aldaki hauek, seinalatu ditugun arrazoiengatik (hau da, espezie oso hurbil edo errepresentagarrien, eta halaber aldaki aintzatetsien, egungo banaketaz dakigunagatik), bitarteko aldeetan berek bigiztatzen dituztenak baino banako gutxiago izanik existituko dira.