CHAPTER X 



On the Imperfection of the Geological Record 



On the Absence cf Intermediate Varieties at the Present Day — On the Na- 

 ture 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 

 Palaeontological Collections — On the Intermittence of Geological Forma- 

 tions — On the Denudation of Granitic Areas — On the Absence of Inter- 

 mediate 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 maintained in this vol- 

 ume. Most of them have now been discussed. One, namely, the 

 distinctness of specific forms and their not being blended to- 

 gether by innumerable transitional links, is a very obvious diffi- 

 culty. I assigned reasons why such links do not commonly occur 

 at the present day under the circumstances apparently most fa- 

 vorable for their presence, namely, on an extensive and continu- 

 ous area with graduated physical conditions. I endeavored 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 condi- 

 tions of life do not graduate away quite insensibly like heat or 

 moisture. I endeavored, also, to show that intermediate varieties, 

 from existing in lesser numbers than the forms which they con- 

 nect, will generally be beaten out and exterminated during the 

 course of further modification and improvement. The main cause, 

 however, of innumerable intermediate links not now occurring 

 everywhere throughout nature, depends on the very process of 

 natural selection, through which new varieties continually take 

 the places of and supplant their parent-forms. But just in pro- 

 portion as this process of extermination has acted on an enor- 

 mous scale, so much the number of intermediate varieties, which 

 have formerly existed, be truly enormous. Why then is not every 

 geological formation and every stratum full of such intermediate 



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