Origin of Species Variorum

Comparison with 1869

To the question why we do not find rich fossiliferous deposits belonging to these assumed earliest periods, I can give no satisfactory answer. Several ... eminent geologists, with Sir R. Murchison at their head, were until recently convinced that we beheld in the organic remains of the lowest Silurian stratum the first dawn of life. .. .. .. Other highly competent judges, as Lyell and .. E. Forbes , have disputed this conclusion. We should not forget that only a small portion of the world is known with accuracy. Not long ago M. Barrande added another and lower stage, ... abounding with new and peculiar species beneath the old Silurian system. Remnants of several forms have also been detected ... beneath Barrande's so-called primordial zone in the Longmynd group, now divided into two stages, and constituting the Lower Cambrian system. Still more recently, the remarkable discovery has been made by Torell of the remains of monocoty-ledonous plants in a Swedish formation, corresponding with the Longmynd group; so that terrestrial or freshwater plants existed several great stages lower down in the series than has hitherto been supposed. The presence also of phosphatic nodules and bituminous matter in some of the lowest azoic rocks, probably indicates life at these periods. Now the great discovery of the Eozoon in the Laurentian formation of Canada has been made, for after reading Dr. Carpenters description of this fossil, it is scarcely possible to doubt regarding its organic nature. ↑ There are three great series of strata beneath the Silurian system in Canada, in the lowest of which the Eozoon was found; and Sir W. Logan states that their "united thickness may possibly far surpass that of all the succeeding rocks, from the base of the palæozoic series to the present time. We are thus carried back to a period so far remote, that the appearance of the so-called Primordial fauna (of Barrande) may by some be considered a comparatively modern event." The Eozoon belongs to the most lowly organised of all classes of animals, but for its class is highly organised; it existed in countless numbers, and, as Dr. Dawson has remarked, certainly preyed on other minute organic beings, which must have lived in great numbers. ↑ Thus the words above given, which I wrote in 1859, and which are almost the same with those used by Sir W. Logan, have come true. Notwithstanding these several facts, the difficulty of assigning any good cause for the absence beneath the Silurian formations of vast piles of strata rich in fossils is very great. It does not seem probable that the most ancient beds have been quite worn away by denudation, or that their fossils have been wholly obliterated by metamorphic action, for if this had been the case we should have found only small remnants of the formations next succeeding them in age, and these would always have existed in a partially metamorphosed condition. But the descriptions which we .. possess of the Silurian deposits over immense territories in Russia and in North America, do not support the view, that the older a formation is, the more it has invariably suffered extreme denudation and metamorphism.

The case at present must remain inexplicable; and may be truly urged as a valid argument against the views here entertained. To show that it may hereafter receive some explanation, I will give the following hypothesis. From the nature of the organic remains, which

To the question why we do not find records of these vast primordial periods, I can give no satisfactory answer. Several of the most eminent geologists, with Sir R. Murchison at their head, are convinced that we see in the organic remains of the lowest Silurian stratum the dawn of life on this planet. Other highly competent judges, as Lyell and the late E. Forbes , dispute this conclusion. We should not forget that only a small portion of the world is known with accuracy. M. Barrande has lately added another and lower stage to the Silurian system, abounding with new and peculiar species. Traces of life have been detected in the Longmynd beds, beneath Barrandes so-called primordial zone. ↑ The presence of phosphatic nodules and bituminous matter in some of the lowest azoic rocks, probably indicates the former existence of life at these periods. But the difficulty of understanding the absence of vast piles of fossiliferous strata, which on my theory no doubt were somewhere accumulated before the Silurian epoch, is very great. If these most ancient beds had been wholly worn away by denudation, or obliterated by metamorphic action, we ought to find only small remnants of the formations next succeeding them in age, and these ought to be very generally in a metamorphosed condition. But the descriptions which we now possess of the Silurian deposits over immense territories in Russia and in North America, do not support the view, that the older a formation is, the more it has always suffered the extremity of denudation and metamorphism.