Origin of Species Variorum

connected all the past and present species of the same group into one long and branching chain of life. We ought only to look for a few links, and such assuredly we do find— some more distantly, some more closely, related to each other; and these links, let them be ever so close, if found in different stages of the same formation, would, by many palæontologists, be ranked as distinct species. But I do not pretend that I should ever have suspected how poor a record of the mutations of life the best pre-served geological section presented, had not the difficulty of our not discovering innumerable transitional links between the species which appeared 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 over-rate 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