The Origin of Species: A Variorum Text

CHAPTER IX.

CHAPTER IX. i t] x. 2 ON THE IMPERFECTION OF THE GEOLOGICAL RECORD. 3 On the absence of intermediate varieties at the present day-On the nature of extinct intermediate varieties; on their numberOn the vast lapse of time, as inferred from the rate of deposition and of denudation-On the poorness of our paleeontological collections-On the intermittence of geological formations-On the absence of intermediate varieties in anyone formationOn the sudden appearance of groups of species-On their sudden appearance in the lowest known fossiliferous strata. 3:c collections-On the denudation of granitic areas-On the intermittence 3:e 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/strata-Antiquity of the habitable earth. 3:/ collections-On the intermittence of geological formations-On the denudation of granitic areas-On the absence 4 IN the sixth chapter I enumerated the chief objections which might be justly urged against the views maintained in this volume. S Most of them have now been discussed. 6 One, namely the distinctness of specific forms, and their not being blended together by innumerable transitional links, is a very obvious difficulty. 7 I assigned reasons why such links do not commonly occur at the present day, under the circumstances apparently most favourable for their presence, namely on an extensive and continuous area with graduated physical conditions. 7:1 day under 8 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. 9 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. 10 The main cause, however, of innumerable intermediate links 475 not now occurring everywhere throughout nature depends on the very process of natural selection, through which new varieties continually take the places of and exterminate their parentforms . rot] nature, depends/places of and supplant their II But just in proportion as this process of extermination has acted on an enormous scale, so must the number of intermediate varieties, which have formerly existed on the earth, be truly enormous. I t :e existed, be 12 Why then is not every geological formation and every stratum full of such intermediate links? 13 Geology assuredly does not reveal any such finely graduated organic chain; and this, perhaps, is the most obvious and gravest objection which can be urged against my theory. I3:C finely-graduated/obvious and serious objection I3:/ against the theory. 14 The explanation lies, as I believe, in the extreme imperfection of the geological record. 15 In the first place it should always be borne in mind what sort of intermediate forms must, on my theory, have formerly existed. I5:e on the theory 16 I have found it difficult, when looking at any two species, to avoid picturing to myself, forms directly intermediate between them. I6:e myself forms 17 But this is a wholly false view; we should always look for forms intermediate between each species and a common but unknown progenitor; and the progenitor will generally have differed in some respects from all its modified descendants. 18 To give a simple illustration: the fantail and pouter pigeons have both descended from the rock-pigeon; if we possessed all the intermediate varieties which have ever existed, we should have an extremely close series between both and the rock-pigeon; but we should have no varieties directly intermediate between the fantail and pouter; none, for instance, combining a tail somewhat expanded with a crop somewhat enlarged, the characteristic features of these two breeds. I8:! pigeons are both descended 19 These two breeds, moreover, have become so much modified, that if we had no historical or indirect evidence regarding their origin, it would not have been possible to have determined from a mere comparison of their structure with that of the rock-pigeon, whether they had descended from this species or from some other allied species, such as C. oenas. 476 I9:c rock-pigeon (C. Iivia), whether Ig:d that, if/determined, from a mere/rock-pigeon, C. livia, whether I9:f allied form, such 20 So with natural species, if...