ABSTRACT
On the absence of intermediate varieties at the present day—On the nature of extinct intermediate varieties; on their numberOn the vast lapse of time, as inferred from the rate of deposition and of denudation—On the poorness of our palæontological collectioas—On the intermittence of geological formationsOn the absence of intermediate varieties in any one formationOn the sudden appearance of groups of species—On their sudden appearance in the lowest known fossiliferous strata.
