Origin of Species Variorum

absence of ... innumerable transitional links between the species which lived at the commencement and close of each formation, pressed so hardly on my theory.

On the sudden Appearance of whole Groups of allied Species .

The abrupt manner in which whole groups of species suddenly appear in certain formations, has been urged by several palæontologists— for instance, by Agassiz, Pictet, and Sedgwick— as a fatal objection to the belief in the transmutation of species. If numerous species, belonging to the same genera or families, have really started into life .. at once, the fact would be fatal to the theory of descent with slow modification through natural selection. For the development of a group of forms, all of which have descended from some one progenitor, must have been an extremely slow process; and the progenitors, must have lived long ages before their modified descendants. But we continually overrate the perfection of the geological record, and falsely infer, because certain genera or families have not been found beneath a certain stage, that they did not exist before that stage. In all cases positive palæontological evidence may be implicitly trusted; negative evidence is worthless, as experience has so often shown. We continually forget how large the world is, compared with the area over which our geological formations have been carefully examined; we forget that groups of species may elsewhere have long existed, and have slowly multiplied, before they invaded the ancient archipelagoes of Europe and .. the United States. We do not make due allowance for the enormous intervals of time which have .. elapsed between our consecutive formations,— longer perhaps in many cases than the time