54 THE ORIGIN OF SPECIES 



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 paleontolog- 

 ical collections — On the intermittence 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 objec- 

 tioDs which might be justly urged against the views 

 maintained in this volume. Most of them have now 

 been discussed. One, namely, the distinctness of specific 

 forms and their not being blended together by innumer- 

 able 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 favorable for their presence, namely, on an exten- 

 sive and continuous area with graduated physical con- 

 ditions. 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 r'^ally governing condi- 

 tions of life do not graduate away quite insensibly like 

 heat or moisture. I endeavored, also, to show that inter- 

 mediate varieties, from existing in lesser numbers than^ 



