IN LOWEST F088ILIFER0 US STRATA. 339 



and violent changes in its physical 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 

 B. Forbes, have disputed this conclusion. ' We should not 

 forget than 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 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, probably indicates life at these 

 periods; and the existence of the Bozoon in the Laurentian 

 formation of Canada is generally admitted. There are three 

 great series of strata beneath the Silurian system in Can- 

 ada, in the lowest of which the Bozoon 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 Bozoon 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. 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 



