If we suppose that an early progenitor-the archetype, as it may be called-of all mammals, birds and reptiles, had its limbs constructed on the existing general pattern, for whatever purpose they served, we can at once perceive the plain signification of the homologous construction of the limbs throughout the class.
Suposatzen baldin badugu ugaztun, hegazti eta narrasti guztien gurasolehenen batek-arketipoa dei dakiokeenak-bere gorputzadarrak oraingo eredu orokorraren arabera eraturik zituela, dena delako helbururako izanik, orduan berehala hauteman genezake klase osoko kideek gorputzadarren erakuntza homologoa izatearen esangura nabaria.