340 AFFINITIES Ob* EXTINCT SPECIES. 



appearance; for the parent rock-pigeon still lives; anu 

 many varieties between the rock-pigeon and the carrier have 

 become extinct ; and carriers which are extreme in the im- 

 portant character of length of beak originated earlier than 

 short-beaked tumblers, which are at the opposite end of the 

 series in this respect. 



Closely connected with the statement, that the organic 

 'remains from an intermediate formation are in some degree 

 intermediate in character, is the fact, insisted on by all 

 palaeontologists, that fossils from two consecutive formations 

 are far more closely related to each other, than are the fossils 

 from two remote formations. Pictet gives as a well-known 

 instance, the general resemblance of the jrganic 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 Professor Pictet in his 

 belief in the immutability of species. He who is acquainted 

 with the distribution of existing species over the globe, will 

 not attempt to account for the close resemblance of distinct 

 species in closely consecutive formations, by the physical 

 conditions of the ancient areas having remained nearly the 

 same. Let it be remembered that the forms of life, at least 

 those inhabiting the sea, have changed almost simultaneously 

 throughout the world, and therefore under the most different 

 climates and conditions. Consider the prodigious vicissi- 

 tudes of climate during the pleistocene period, which in- 

 cludes 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 

 remains from closely consecutive formations being closely 

 related, though ranked as distinct species, is obvious. As 

 the accumulation of each formation has often been inter- 

 rupted, and as long blank intervals have intervened between 

 successive formations, 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 varieties between the 

 species which appeared at the commencement and close of 

 these periods : but we ought to find after intervals, very long 

 as measured by years, but only moderately long as measured 

 geologically, closely allied forms, or, as they have been called 

 by some authors, representative species ; and these assuredly 

 we do find. We find, in short, such evidence of the slow 

 and scarcely sensible mutations of specific forms, as we have 

 the right to expect. 



