There can be no doubt that the existing Fauna and Flora is but the last term of a long series of equally numerous contemporary species, which have succeeded one another, by the slow and gradual substitution of species for species, in the vast interval of time which has elapsed between the deposition of the earliest fossiliferous strata and the present day.
Thomas Henry Huxley, The Advance of Science in the Last Half-Century
biology, doubt, evolution, extinction, fauna, flora, flora-and-fauna, fossil, geology, science, species, strata, time