I may here recall a remark formerly made, namely, that it might require a long succession of ages to adapt an organism to some new and peculiar line of life, for instance, to fly through the air; and consequently that the transitional forms would often long remain confined to some one region;
Lehen eginiko ohar bat gogorarazi nahi dut hemen, hau da, aroen hurrenketa luze bat beharko zela organismo bat bizimodu berri eta berezi batera egokitzeko, adibidez, airean zehar hegaz egiteko, eta beraz, iragaitzazko formak herrialde batera mugaturik egonen zirela;