334 ORIGIN OF SPECIES 



termination has acted on an enormous scale, so must the 

 number of intermediate varieties, which have formerly ex- 

 isted, be truly enormous. Why then is not every geological 

 ^formation and every stratum full of such intermediate links? 

 Geology assuredly does not reveal any such finely-graduated 

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

 serious objection which can be urged against the theory. The 

 explanation lies, as I believe, in the extreme imperfection 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 loolcing at any two 

 species, to avoid picturing to myself forms directly intermedi- 

 ate between them. 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. 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. Hvia, whether they had de- 

 scended from this species or from some other allied form, 

 such as C. oenas. 



So, with natural species, if we look to forms very distinct, 

 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 organisation 

 much general resemblance to the tapir and to the horse; but 

 in some points of structure may have differed considerably 

 from both, even perhaps more than they differ from each 



