GEO LOGICAL RECORD. 31;^ 



just in proportion as this process of extermination lias 

 acted on an enormous scale, so must the number of inter- 

 mediate varieties, which have formerly existed, be truly 

 enormous. Why then is not every geological formation 

 and every stratum full of such intermediate links? Geo- 

 logy assuredly does not reveal any such tlnelv-graduated 

 organic chain; and this, perhaps, is the most obvious and 

 serious objection Avhich can be urged against the theory. 

 The explanation lies, as I believe, in the extreme imper- 

 fection of the geological record. 



In the first place, it should always be borne in mind 

 what sort of intermediate forms must, on the theory, have 

 formerly existed. I have found it difficult, when looking 

 at any two species, to avoid picturing to myself forms 

 directly intermediate between them. But this is a wlu^lly 

 false view; we should always look for forms intermediate 

 between each species and a common but unknown pro- 

 genitor; and the progenitor will generally have dilTei-ed in 

 some respects from all its modified descendants. To give 

 a simple illustration: the fantail and pouter pigeons are 

 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. 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, C. livia, 

 whether they had descended from this species or from 

 some other allied form, such as 0. oenas. 



So, with natural species, if we look to forms very dis- 

 tinct, for instance to the horse and tapir, we have no 

 reason to suppose that links directly intermediate between 

 them ever existed, but between each and an unknown 

 common parent. The common parent will have had in its 

 whole organization much general resemblance to the tapir 

 and to the horse; but in some points of structure may 

 have differed considerably from both, even perhaps mora 



