122 DARWINISM AND THE PROBLEMS OF LIFE 



For the simple reason that, though these strata are 

 the oldest known to us, they really represent terrestrial 

 epochs that had many predecessors ; but we have no 

 documents relating to these periods. The book of the 

 history of organisms only opens for us when there is 

 already an immense wealth of forms on the earth. 

 Besides fishes, there are crabs, mussels, and other 

 animals, the development of which from the lowest 

 organisms must have taken enormous periods of time. 

 At first there must have been merely particles of 

 living substance, and in comparison with the couritless 

 series of modifications that lead from one of these to the 

 fish, the very much shorter series between the fish and 

 the mammal is insignificant. We may say, therefore, 

 that the pages of the archives of the earth's history that 

 have been preserved only relate to the "modern period" 

 of organic life, and that " antiquity" and the " Middle 

 Ages" are lost to us, and will never be recovered. 



The earlier of the geological strata lie below the 

 later ; the most recent lie at the top of all. As 

 geologists penetrated deeper and deeper in their 

 examination of the strata, and still found animal 

 remains in the earliest deposits, there suddenly appeared, 

 below the earliest fossiliferous layer, one that had no 

 organic remains whatever. Experts still differ about 

 these empty masses of rock. Many regard them as 

 the crust that was formed when the surface of our 

 planet, at that time a mass of molten liquid, cooled 

 down. At this period of incandescence there cannot 

 have been any living things, and we ask for the strata 

 that lie between this crust and the deposit that contains 



