THE THEOKY OF EVOLUTION 



Formation Groups. Formations. 



/Chalk | Upper Chalk with many grades 



( Lower Chalk 



Secondary 



Malm 



Jura | Dogger 



vLias 



[Keuper 

 VTrias j Mussel Chalk 



(New Eed Sandstone 



TW<- a /-P \ (Permian Limestone 

 JJyas (rerm.) i - T i n -, 



' (Old Eed Sandstone 



Carboniferous 



Primary . . . . _ 



Devonian 



Silurian 

 Cambrian 



To these are to be added now the pre- Cambrian 

 (Algonkium). Under these lie gneiss and mica slate. 



The first fossiliferous formations are the so-called 

 pre-Cambrian. The primary rocks (gneiss and crystal- 

 line slate), upon which the pre-Cambrian sediments lie, 

 conceal no organic petrifactions of any kind at all. 1 

 It must therefore be accepted that, in the seas in which 

 the oldest sediments were deposited, life really appeared 

 in the first place. That must have happened very 

 long ago, since, if we imagine all the formations super- 

 posed on each other, the total would be of a thickness 

 of about 200 kilometres about 120 miles. 



1 With regard to the alleged fossils of the Primary rocks see Kayser : 

 Lefirbucli der Geolog. Formationskunde, p. 21. The freedom from fossils of 

 the Primary rocks ' is only temporarily shaken ' at first by the Eozoon 

 Canadense, which was recognized as serpentine excrescences. Since then 

 other assumed traces of organisms have deceptively appeared, but the 

 Primary rocks must be again, as previously, regarded as entirely free from 

 fossils ; * also the presence of lime or graphite does not imply organic life, 

 since both have been proved to be able to originate also on inorganic lines.' 



