38 The Make-Up and the Wordings of the Earth 



seed-plants are found for the first time only in more recent 

 deposits. 



The fact that lower types of plants and animals are 

 recognized in the oldest layers, and progressively higher types 

 in more recent layers, is quite in harmony with Cuvier's view 

 that after each supposed cataclysm a completely new flora 

 and a completely new fauna had been created. It shows 

 perhaps a progressive " improvement " in the living inhabit- 

 ants of the earth, but it does not show evolution in the sense 

 in which the term is today used by scientists. It is necessary 

 to find evidence of genetic continuity or relationship by de- 

 scent from age to age. 



Was there Continuity of Life? 



We have seen that the fossil record is incomplete, and 

 that, from the nature of the case, it must remain incomplete, 

 no matter how thoroughly the fossil hunters explore every 

 accessible cubic foot of the earth's crust. The shells and 

 skeletons of animals that lie buried in the slime at the bot- 

 tom of lakes and seas come in the course of time to be " fos- 

 sils," but only after that portion of the bottom has been 

 raised above the water level and consolidated into rock. An- 

 other layer of sediment is formed after long lapse of time 

 only after the surface is again submerged or flooded over, 

 and the new covered bottom is in turn again raised aloft by 

 the slow movements of the ocean floor or of continental 

 masses. There must therefore be a break between the 

 life forms of one layer and those of the next. The very 

 conditions that brought about the formation of separate 

 layers meant not only inconceivably long periods of time, 

 but radically changed physical conditions, involving differ- 

 ent kinds of plants and animals. We should expect, at best, 

 that plants and animals forced by the changing conditions 

 to shift to a more congenial region would leave their remains 

 in areas remote from those containing the fossils of their an- 

 cestors, rather than in the immediately succeeding strata. 



