114 AFFINITIES OF EXTINCT SPECIES. [Chap. XL 



mediate in age. But supposing for an instant, in this 

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

 ance and disappearance of the 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 principal 

 living and extinct races of the domestic pigeon were 

 arranged in serial affinity, this arrangement would not 

 closely accord with the order in time of their produc- 

 tion, and even less with the order of their disappearance ; 

 for the parent rock-pigeon still lives ; and many varieties 

 between the rock-pigeon and the carrier have become 

 extinct ; and carriers which are extreme in the impor- 

 tant 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 resem- 

 blance of the organic remains from the several stages 

 of the Chalk formation, though the species are dis- 

 tinct in each stage. Tins 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, 



