m LO WEST FOSSILIFEHO US STRA TA. 339 



and violent changes in its physical conditions than tlioso 

 now occurring; and such changes would have tended to 

 induce changes at a corresponding rate in the or^'anisma 

 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 tiiat we beheld in tlie 

 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 shoiild not 

 forget than only a small portion of the world is known with 

 accuracy. Not very lon^ ago M. Barrande added anotiier 

 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, ^Ir. Hicks 

 has found South Wales beds rich in trilobites, and con- 

 taining various molluscs and annelids. The presence of 

 phosphatic nodules and bituminous matter, even in some 

 of the lowest azotic rocks, probablv indicates life at tliese 

 periods; and the existence of the Eozoon in the Lauren tiaii 

 formation of Canada is generally adinitted. There are three 

 great series of strata beneath the Silurian system in Can- 

 ada, 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 tho 

 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 organized 

 of all classes of animals, but is highly organized 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. Tims 

 the words, which I wrote in 1S59, about the existence of 

 living beings long before the Cambrian perio<l, 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 



