Origin of Species Variorum

Comparison with 1869

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. Not long ago M. Barrande added another and lower stage to the Silurian system, abounding with new and peculiar species beneath the old Silurian system. Traces of life have been detected in the Longmynd beds beneath Barrande's so-called primordial zone. 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, about the vast periods which had probably elapsed before the Cambrian system, are almost the same with those used by Sir W. Logan. .. .. .. Nevertheless the difficulty of assigning any good cause for the absence beneath the Upper Cambrian formations of vast piles of strata rich in fossils 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 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,

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 very long ago M. Barrande added another and lower stage, ... abounding with new and peculiar species, beneath the then known Silurian system; and now, still lower down in the Lower Cambrian formation, Mr. Hicks has found in South Wales beds rich in trilobites, and containing various molluscs and annelids. ↑ The presence .. of phosphatic nodules and bituminous matter, even in some of the lowest azoic rocks, probably indicates life at these periods; and the existence of the Eozoon in the Laurentian formation of Canada is generally admitted. There are three great series of strata beneath the Silurian system in Canada, in the lowest of which the Eozoon is found. .. 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 .. remote, that the appearance of the so-called Primordial fauna (of Barrande) may by some be considered .. as a comparatively modern event." The Eozoon belongs to the most lowly organised of all classes of animals, but is highly organised for its class; 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, .. which I wrote in 1859, about the existence of living beings long before the Cambrian period, and which are almost the same with those since used by Sir W. Logan, have proved true. Nevertheless, the difficulty of assigning any good reason for the absence ... of vast piles of strata rich in fossils beneath the Cambrian system 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 invariably it has suffered extreme denudation and metamorphism.