CuAP. IX. GEOLOGICAL RECORD. 267 



is not every pfColor;ical formation and every stratum full of 

 such iiitermcdiate links V GeolojTy assuredly does not reveal 

 any such tinclv-^radiiated organic; chain; and this, perhaps, is 

 the most obvious and serious objection which can be urf^ed 

 ar^ainst the theor3^ 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 tiieory, have formerly 

 existed. I have found it diilicult, when looking at any two 

 species, to avoid picturing to myself forms directbj intermedi- 

 ate between them. But this is a wholly false view ; we should 

 alwa3's look for forms intermediate between each species and 

 a common but unknown progenitor ; and the progenitor will 

 generally have ditlered in some respects from all its modified 

 descendants. 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 jiouter ; 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 re- 

 garding their origin, it would not have been possible to have 

 determined, from a mere comparison of their structure with 

 tliat of the rock-pigeon, C. livia, whether they had descended 

 irom this species or from some other allied species, 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 sup>- 

 pose that links ever existed directly intermediate between 

 them, but between each and an unknown connnon parent. The 

 common parent will have had in its whole; organization much 

 general resemblance to the tapir and to the horse ; but in some 

 ])oints of structure may have difTcMcd considerably from both, 

 even perhaps more than they differ from each other. Hence, 

 in all such cases, we should be unable to recognize the parent- 

 form of any two or more s])ecies, even if we closely compared 

 the structure of the parent with that of its modified descend- 

 ants, unless at the same time we had a nearly jierfect chain of 

 the intermediate links. 



It is just possible by the theory that one of two living 



