VI CONTENTS 



Non-living and living in biology 42 



Non-living and living in geology 44 



Chemical uniformity of present mode of life 45 



Impossibility of natural synthesis of organic compounds in 



the atmosphere 46 



The oxygenic atmosphere of the present 47 



Anoxygenic primeval atmosphere 48 



Inorganic synthesis of 'organic' compounds in primeval 



atmosphere 48 



Generatio spontanea 50 



Experimental checks 51 



Chemical diversity of early 'life': the Pirie drawing ... 57 



Mutants acquiring a new skill: organic photosynthesis . 59 



Gradual transition from primeval to present atmosphere . 60 



The astronomer's view 61 



Chapter V. the tw^o atmospheres: anoxygenic and oxygenic, 



PRE-ACTUALISTIC AND ACTUALISTIC 62 



Aerobic and anaerobic, oxygenic and anoxygenic ... 62 



Aradiatic for shorter ultraviolet light 63 



Pre-actualistic and actualistic 63 



Exogenic and endogenic processes 64 



Actualism in early exogenic and endogenic processes . . 65 



Chapter VI. where to look for remains of early life: the 



OLD shields 67 



Paucity of early records 67 



The old shields 70 



Stability of old shields 72 



Complex structure of old shields 73 



Chapter VII. the fossils 75 



Late pre-Cambrian faunae 75 



The importance of microbes 75 



Early pre-Cambrian remains 76 



The oldest biogenic deposits 77 



Anoxygenic metabolism of earliest known organisms . . 82 



Structures in biogenic and inorganic limestone deposits . 82 



The oldest real fossils 83 



Primitive plants from Ontario 85 



