156 



DEVELOPMENT OF ORGANIC LIFE 



[Ch. IX 



v. 



up. 



the earth's surface. After many geographical revolutions 

 after the sinking down of ancient continents and the 

 heaval of newer ones, it is natural that the strata of a verv 

 remote age should coincide generally with the bed of the 

 ancient ocean, rather than with the space which was occupied 

 by land. The reader will perhaps be better able to appreciate 

 the difficulty which, according to the doctrine of chances 

 will usually attend a search for the fossil 

 inhabitants of ancient lands — those, for example, of the primary 



memorials 



periods 



map 



He will 



here observe that the areas distinguished by dark shading 

 represent the only spots on the globe where there is now land 

 exactly opposite to land. Let us imagine these dark spots 

 instead of expressing the site of contemporaneous antipodal 

 land, to represent the spaces where paleozoic land of Silurian 

 or Cambrian date may have happened to coincide with a 

 portion of our present continents and islands. The amount 

 of such coincidence must strike the reader as limited in the 

 extreme ; but its amount is by no means improbable, for the 

 contrast of two opposite hemispheres, in regard to the distri- 

 bution of land and sea, at one and the same time, would on 



B 



resemble 



distribution would characterise the same hemisphere in two 

 very distant ages. Well therefore may we despair of gaining 

 more than a superficial acquaintance with the terrestrial 

 plants and air-breathing animals which once belonged to 

 those small shaded areas. If they had never been submerged 

 from the earliest period, they would have suffered such 

 denudation by rain and rivers, both when the land was 

 stationary or when it was undergoing changes of level, that 

 no parts of the old surface, or of its lacustrine and fluviatile 

 deposits, would remain. Our best chance of hitting upon the 

 spots where some monuments of such early times have 

 escaped destruction, would arise from the submergence of the 

 shaded spots, and the accumulation of marine strata upon 



them, or upon the littoral deposits found in the immediate 

 neighbourhood. Even then we could only obtain access to 

 the buried strata, whether fresh-water or littoral, at those 

 points where they had been exposed to view by the partial 





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