CHAPTER X 

 On the Imperfection of the Geological Record 



On the absence of intermediate varieties at the present day — On the 



nature of extinct intermediate varieties ; on their number — On 

 the lapse of time, as inferred from the rate of denudation and 

 of deposition — On the lapse of time as estimated by years — 

 On the poorness of our palseontological collections — On the in- 

 termittence of geological formations — On the denudation of 

 granitic areas — On the absence of intermediate varieties in any 

 one formation — On the sudden appearance of groups of species 

 — On their sudden appearance in the lowest known fossiliferous 

 strata — Antiquity of the habitable earth. 



IN the sixth chapter I enumerated the chief objections 

 which might be justly urged against the views main- 

 tained in this vohime. Most of them have now been dis- 

 cussed. One, namely the distinctness of specific forms, and 

 their not being blended together by innumerable transitional 

 links, is a very obvious difficulty. I assigned reasons why 

 such links do not commonly occur at the present day under 

 the circumstances apparently most favourable for their pres- 

 ence, namely on an extensive and continuous area with grad- 

 uated physical conditions. I endeavoured to show, that the 

 life of each species depends in a more important manner on 

 the presence of other already defined organic forms, than on 

 climate, and, therefore, that the really governing conditions 

 of life do not graduate away quite insensibly like heat or 

 moisture. I endeavoured, also, to show that intermediate va- 

 rieties, from existing in lesser numbers than the forms which 

 they connect, will generally be beaten out and exterminated 

 during the course of further modification and improvement. 

 The inain cause, however, of innumerable intermediate links " 

 not now occurring everywhere throughout nature, depends on 

 the very process of natural selection, through which new va- 

 rieties continually take the places of and supplant their 

 parent-forms. But just in proportion as this process of ex- 



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