THE APPEARANCE OF LIFE ON THE GLOBE 319 



the artificial production of cells analogous, at least 

 morphologically, to those which constitute living 

 beings.* 



The geological problem of the beginnings of 

 life is more modest and at the same time more 

 positive. In order to handle it profitably, it will be 

 necessary to draw up, like a scrupulous and exact 

 historian, an inventory of the documentary proofs 

 we possess at the present day regarding the most 

 ancient traces of living beings, patiently exhumed 

 one by one from the lowest strata of the sedimentary 

 crust of the globe. 



If we look back as far as the middle of the past 

 century, we shall observe that, at that epoch, the 

 strata containing the remains of the earliest fossil 

 beings known to us corresponded to that part of the 

 Primary era which geologists have called since the 

 days of Murchison the Silurian period, from the 

 Silurian tribe who, at the Anglo-Roman epoch, 

 inhabited the present county of Shropshire. These 

 Silurian strata of the north-west of England are 

 very rich in remains of marine organisms, and, as 

 far back as 1840, the illustrious geologist, Murchison, 

 published, under the title of Siluria, a work which 

 is still classic, wherein were catalogued and de- 

 scribed about 950 species of fossil animals belonging 

 to nearly all the fundamental divisions of the animal 

 kingdom. 



The Silurian fauna comprises, in fact, among the 

 Invertebrates, silicious Sponges; numerous Polyps 



* See especially the experiments of M. Stephane Leduc reproduced 

 in M. Gustave Le Bon's Evolution of Forces, Vol. XCI of this Series, 

 pp. 359-360 and Pis. 41-42. ED. 



