312 AFFINITIES OF EXTINCT SrECIES. Chap. X. 



ten-estrial productions inliabiting separated districts. To com- 

 pare small tliiii;^s with p^reat : if the principal living and ex- 

 tinct races of the domestic pigeon were arranged as well as 

 they could be in serial affinity, this arrangement would not 

 accord closely with the order in time of their production, and 

 even less with the order of their disappearance ; for the par- 

 cnt-rock-pigeon still lives ; and many varieties between the 

 rock-pigeon and the carrier have become extinct ; and carriers 

 Avhich are extreme in the important character of length of 

 beak originated earlier than short-beaked tumblcrs,which are 

 at the opposite end of the series in this respect. 



Closely connected with tlie statement that the organic re- 

 mains from an intermediate formation are in some degree in- 

 termediate in character, is the fact, insisted on by all paleon- 

 tologists, that fossils from two consecutive formations are far 

 more closclj' related to each other than are the fossils from 

 two remote formations. Pictet gives us a well-known in- 

 stance, the general resemblance of the organic remains from 

 the several stages of the Chalk formation, though the species 

 are distinct in each stage. This fact alone, from its generality, 

 seems to have shaken Prof. Pictet in his firm belief in the im- 

 mutability of species. He who is acquainted with the distribu- 

 tion of existing species over the globe, will not attempt to 

 account for the close resemblance of distinct species in close- 

 ly consecutive formations, by the ph^-sical conditions of the 

 ancient areas having remained nearly the same. Let it be re- 

 membered that the forms of life, at least those inhabiting the 

 sea, have changed almost simultaneously throughout the Avorld, 

 and therefore under the most different climates and conditions. 

 Consider the prodigious vicissitudes of climate during the pleis- 

 tocene period, which includes the whole glacial epoch, and note 

 how little the specific forms of the inhabitants of the sea have 

 been affected. 



On the theory of descent, the full meaning of the fossil re- 

 mains from closely-consecutive formations being closely related, 

 though ranked as distinct species, is obvious. As the accumu- 

 lation of each formation has often been interrupted, and as 

 long blank intervals have intervened between successive forma- 

 tions, we ought not to expect to find, as I attempted to show 

 in the last chapter, in any one or in any two formations all the 

 intermediate vaiietics between the species which appeared at 

 the commencement and close of these periods : but we ought 

 to find after intervals, very long as measureil by years, but 



