298 GEOLOGICAL CONTEMPORANEITY ix 



less differentiated, than Beryx lincatus of King 

 George's Sound ? 



Or to turn to the higher Vertebrata — in what 

 sense are the Liassic Chelonia inferior to those 

 which now exist ? How are the Cretaceous 

 Ichthyosauria, Plesiosauria, or Pterosauria less 

 embryonic, or more differentiated, species than 

 those of the Lias ? 



Or lastly, in what circumstance is the PJiasco- 

 lotherium more embryonic, or of a more genera- 

 lised type, than the modern Opossum; or a 

 ZoijhiGdoi, or a Fala3othermmj than a modern 

 Taijirus or Hyrax'^ 



These examples might be almost indefinitely 

 multiplied, but surely they are sufficient to prove 

 that the only safe and unquestionable testimony 

 we can procure — positive evidence — fails to dem- 

 onstrate any sort of progressive modification 

 towards a less embryonic, or less generahsed, type 

 in a great many groups of animals of long- 

 continued geological existence. In these groups 

 there is abundant evidence of variation — none of 

 what is ordinarily understood as progression ; and, 

 if the known geological record is to be regarded 

 as even any considerable fragment of the whole, 

 it is inconceivable that any theory of a necessarily 

 progressive development can stand, for the numer- 

 ous orders and families cited afford no trace of 

 such a process. 



But it is a most remarkable fact, that, while the 



