Note 310 — Chapter VI · —Geographical Area
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The preponderant migration of animals from the northern to the southern hemisphere is attributed by Darwin to the greater extent of land in the north, whereby the northern types have existed in greater numbers and have been so perfected through natural selection and competition, that they have surpassed the southern forms in dominating power and therefore have encroached successfully.310 Also the races and nations of the northern continents have seriously invaded the southern land-masses and are still expanding. It is the largest continent, Eurasia, which has been the chief center of dispersal.