Origin of Species Variorum

Comparison with 1866

and have oftenest given rise to new species; and that varieties have at first often been local. All these causes taken conjointly, must have tended to make the geological record extremely imperfect, and will to a large extent explain why we do find many links between the species of the same group— we do not find interminable varieties, connecting together all the extinct and existing forms of life by the finest graduated steps. It should also be constantly borne in mind that any linking varieties between two or more forms, which might be found, would be ranked, unless the whole chain could be perfectly restored, as so many new and distinct species; for it is not pretended that we have any sure criterion by which species and varieties can be discriminated.

He who rejects these views on the nature of the geological record, will rightly reject my whole theory. For he may ask in vain where are the numberless transitional links which must formerly have connected the closely allied or representative species, found in the several stages of the same great formation. He may disbelieve in the enormous intervals of time which have elapsed between our consecutive formations; he may overlook how important a part migration must have played, when the formations of any one great region alone, as that of Europe, are considered; he may urge the apparent, but often falsely apparent, sudden coming in of whole groups of species. He may ask where are the remains of those infinitely numerous organisms which must have existed long before the first bed of the Silurian system was deposited: We now know that animals, and probably plants, lived at an epoch immensely remote, long anterior to the primordial zone of the Silurian system, but I can answer the above question only hypothetically, by saying that as far as we can see, where our oceans now extend they have for an enormous period extended, and where our oscillating continents now stand they have stood ever since the commencement of the Silurian epoch; but that long before that period, the world may have presented a wholly different aspect; and that the older continents, formed of formations older than any known to us, may now all be in a metamorphosed condition, or may lie wholly buried under the ocean.

Passing from these difficulties, all the other great leading facts in palæontology seem to me simply to follow on the theory of descent with modification through natural selection. We can thus understand how it is that new species come in slowly and successively; how species of different classes do not necessarily change

frequently, and have oftenest given rise to new species; .. that varieties have at first .. been local; and lastly, although each species must have passed through numerous transitional stages, it is probable that the periods, during which each underwent modification, though many and long as measured by years, have been short in comparison with the periods during which each remained in an unchanged condition. .. These causes, taken conjointly, ... will to a large extent explain why— though we do find many links— we do not find interminable varieties, connecting together all .. extinct and existing forms .. by the finest graduated steps. It should also be constantly borne in mind that any linking variety between two .. forms, which might be found, would be ranked, unless the whole chain could be perfectly restored, as a new and distinct species; for it is not pretended that we have any sure criterion by which species and varieties can be discriminated.

He who rejects this view of the imperfection of the geological record, will rightly reject the whole theory. For he may ask in vain where are the numberless transitional links which must formerly have connected the closely allied or representative species, found in the successive stages of the same great formation? He may disbelieve in the immense intervals of time which must have elapsed between our consecutive formations; he may overlook how important a part migration has played, when the formations of any one great region, .. as those of Europe, are considered; he may urge the apparent, but often falsely apparent, sudden coming in of whole groups of species. He may ask where are the remains of those infinitely numerous organisms which must have existed long before the Cambrian system was deposited? We now know that at least one animal did then exist; but I can answer this last question only .. by supposing that ... where our oceans now extend they have extended for an enormous period, and where our oscillating continents now stand they have stood .. since the commencement of the Cambrian system; but that, long before that epoch, the world .. presented a widely different aspect; and that the older continents, formed of formations older than any known to us, exist now only as remnants in a metamorphosed condition, or .. lie still buried under the ocean.

Passing from these difficulties, .. the other great leading facts in palæontology agree admirably with the theory of descent with modification through variation and natural selection. We can thus understand how it is that new species come in slowly and successively; how species of different classes do not necessarily change