36,'J AFFINITIES OF EXTINCT SPECIES. 



acter, intermediate in age. Bat supposing for an instant, in 

 this and other such cases, that the record of the first appear- 

 ance and disappearance of ths species was complete, which 

 is far from the case, we have no reason to believe that forms 

 successively produced necessarily endure for corresponding 

 lengths of time. A very ancient form may occasionally have 

 lasted much longer than a form elsewhere subsequently 

 produced, especially in the case of terrestrial productions 

 inhabiting separated districts. To compare small things 

 with great; if the principle living and extinct races of the 

 domestic pigeon were arranged in serial affinity, this ar- 

 rangement would not closely accord with the order in time 

 of their production, and even less with the order of their 

 disappearance; for the parent roclc-pigeon still lives; and 

 many varieties between the rock-pigeon and the carrier 

 have become extinct; and carriers which are extreme in 

 the important 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 

 palEeontologists, that fossils from two consecutive forma- 

 tions 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 

 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 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 prodig- 

 ious viscisitudes of climate during the pleistocene period, 

 which includes the whole glacial epoch, and note how 

 little the specific forms of the inhabitants of the sea have 

 been afEected. 



