I am well aware that the advocates of the development-theory do not state their views as I have here presented them.  On the contrary, they protest against any idea of sudden, violent, abrupt changes, and maintain that by slow and imperceptible modifications during immense periods of time these new types have been introduced without involving any infringement of the ordinary processes of development; and they account for the entire absence of corroborative facts in the past history of animals by what they call the “imperfection of the geological record.”  Now, while I admit that our knowledge of geology is still very incomplete, I assert that just where the direct sequence of geological deposits is needed for this evidence, we have it.  The Jurassic beds, without a single modern scaly Fish, are in immediate contact with the Cretaceous beds, in which the Fishes of that kind are proportionately almost as numerous as they are now; and between these two sets of deposits there is not a trace of any transition or intermediate form to unite the reptilian Fishes of the Jurassic with the common Fishes of the Cretaceous times.  Again, the Cretaceous beds in which the crowded banks of Rudistes, so singular and unique in form, first make their appearance, follow immediately upon those in which all the Bivalves are of an entirely different character.  In short, the deposits of this year along any sea-coast or at the mouth of any of our rivers do not follow more directly upon those of last year than do these successive sets of beds of past ages follow upon each other.  In making these statements, I do not forget the immense length of the geological periods; on the contrary, I fully accede to it, and believe that it is more likely to have been underrated than overstated.  But let it be increased a thousand-fold, the fact remains, that these new types occur commonly at the dividing line where one period joins the next, just on the margin of both.

For years I have collected daily among some of these deposits, and I know the Sea-Urchins, Corals, Fishes, Crustacea, and Shells of those old shores as well as I know those of Nahant Beach, and there is nothing more striking to a naturalist than the sudden, abrupt changes of species in passing from one to another.  In the second set of Cretaceous beds, the Neocomian, there is found a little Terebratula (a small Bivalve Shell) in immense quantities:  they may actually be collected by the bushel.  Pass to the Urgonian beds, resting directly upon the Neocomian, and there is not one to be found, and an entirely new species comes in.  There is a peculiar Spatangus (Sea-Urchin) found throughout the whole series of beds in which this Terebratula occurs.  At the same moment that you miss the Shell, the Sea-Urchin disappears also, and another takes its place.  Now, admitting for a moment that the later can have grown out of the earlier forms, I maintain, that, if this be so, the change is immediate, sudden, without any gradual transitions, and is, therefore, wholly inconsistent with all our known physiological laws, as well as with the transmutation-theory.