1899 C. CALLAWAY — ON EARLIEST LIFE 83 



rocks, and the probability of their destruction is much 

 greater. 



As denudation destroys, metamorphism obUterates. 

 Sedimentary Archtcan rocks have been metamorphosed 

 oftener than newer formations. They have more fre- 

 quently sunk down to deeper and more heated zones of 

 the crust, and been exposed to the pressures which so 

 profoundly modify original structure. It is rare indeed 

 for fossil remains to survive the complete metamorphism 

 of the strata in which they were imbedded. 



Of one thing we maybe certain. The earliest forms of 

 life were the lowest. If we wish to people the Archaean 

 seas with their original inhabitants we must supply them 

 with seaweeds, Foraminifera, sponges, Radiolaria, jelly- 

 fishes, annelids, simple forms of Crustacea and Mollus- 

 coidea, and probably many of the Mollusca proper. But 

 we cannot doubt that a large proportion of the Archaean 

 faunas consisted of animals the very types of which have 

 no modern counterparts. Just as amongst the Mesozoic 

 vertebrates creatures lived which were neither birds nor 

 reptiles, but were the ancestors of both, so in Archaean 

 times there probably existed animals of generalised types, 

 which by gradual differentiation gave rise to the forms 

 now- called annelid, or crustacean, or mollusc. A blind dull 

 life they must have lived, these Archaean tenants of the 

 deep ; but let us not despise them, for w^ithout them we 

 could not have been. 



