CHAP. X.J IN LOWEST FOSSILIFEROUS STRATA. 269 



conditions than those now occurring; and such changes would 

 have tended to induce changes at a corresponding rate in the 

 organisms which then existed. 



To the question why we do not find rich fossiliferous deposits 

 belonging to these assumed earliest periods prior to the Cambrian 

 system, 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 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 palaeozoic 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 organ- 

 ised 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 for- 

 mations 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 



