apparently sudden appearance of groups of allied, and by no means absolutely primordial, species in the lowest fossiliferous strata then known. Thirdly, there was the sudden disappearance of whole groups of species at the end of certain geological periods, and their sudden replacement in the next period by species different in type from the former, and closely allied to one another. These two points—the second and third—were the especial contribution of the Cuvierian school to the controversy. Out of Cuvier's doctrine of the abrupt extinction of faunas at the successive "revolutions of the globe," his disciples had elaborated the theory of the radical and world-wide discontinuity of the faunas and floras of the successive great periods, and had hence inferred the actual necessity of assuming a definite number of special creations of fresh organic worlds en bloc. D'Orbigny knew exactly how many such creations there had been:
The first creation shows itself in the Silurian stage. After its annihilation through some geological cause or other, a second creation took place a considerable time after, in the Devonian stage; and twenty-seven times in succession distinct creations have come to repeople the whole earth with its plants and animals, after each of the geological disturbances which destroyed everything in living nature. Such is the fact, certain but incomprehensible, which we confine ourselves to stating, without endeavoring to solve the superhuman mystery which envelops it."[1]
Fourthly—to continue the enumeration of the paleontological difficulties—it was objected that, especially within the limits of single great geological formations, the arrangement of fossils in the strata did not exhibit the required order of progression from lower to higher types, but sometimes even reversed that order. This was Sedgwick's principal point in his Edinburgh Review article, as it was that of Hugh Miller in his "Footprints of the Creator," 1849, the most widely circulated of the replies to the "Vestiges." Miller's argument may be summarized in his own words.[2] The latest discoveries in the Silurian and Cambrian series, he declared, do not show the
