The degrees of dissimilarity will depend on the migration of the more dominant forms of life from one region into another having been more or less effectually prevented, at periods more or less remote-on the nature and number of the former immigrants-and on the action of the inhabitants on each other in leading to the preservation of different modifications;
Ezberdintasun graduak honako hauen mende egonen dira, alegia, nagusi diren forma organikoen migrazioa herrialde batetik bestera, efikazia handiago edo txikiagoz galarazi izanaren mende, lehenengo inmigrarien izaera eta kopuruaren mende, eta biztanleek, eraldaketa ezberdinak kontserbatzea lortzeko, elkarrengan duten eraginaren mende;