Chap. IX. IMPERFECTION OF GEOLOGICAL RECORD. 279 



CHAPTEK IX. 



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 vast lapse of time, as inferred from the rate of deposi- 

 tion and of denudation — On the poorness of our palEeontological 

 collections — On the intermittence of geological formations — 

 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. 



In the sixth chapter I enumerated the chief objections 

 which might be justly urged against the views main- 

 tained in this volume. Most of them have now been 

 discussed. One, namely the distinctness of specific 

 forms, and their not being blended together by innu- 

 merable transitional links, is a very obvious difficulty. 

 I assigned reasons why such links do not commonly 

 occur at the present day, under the circumstances ap- 

 parently most favourable for their presence, namely 

 on an extensive and continuous area with graduated 

 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 go- 

 verning conditions of life do not graduate away quite 

 insensibly like heat or moisture. I endeavoured, also, 

 to show that intermediate varieties, 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 

 main cause, however, of innumerable intermediate links 

 not now occurring everywhere throughout nature de- 



