IX GEOLOGICAL CONTEMPORANEITY 303 



positive evidence which are worthy of particular 

 notice. 



What then does an impartial survey of the 

 positively ascertained truths of paleontology testify 

 in relation to the common doctrines of progressive 

 modification, which suppose that modification to 

 have taken place by a necessary progress from 

 more to less embryonic forms, or from more to 

 less generalised types, within the limits of the 

 period represented by the fossiliferous rocks ? 



It negatives those doctrines ; for it either 

 shows us no evidence of any such modification, or 

 demonstrates it to have been very slight ; and as 

 to the nature of that modification, it yields no 

 evidence whatsoever that the earlier members of 

 any long-continued group were more generalised 

 in structure than the later ones. To a certain 

 extent, indeed, it may be said that imperfect 

 ossification of the vertebral column is an em- 

 bryonic character; but, on the other hand, it 

 would be extremely incorrect to suppose that the 

 vertebral columns of the older Vertebrata are in 

 any sense embryonic in their whole structure. 



Obviously, if the earliest fossiliferous rocks now 

 known are coeval with the commencement of life, 

 and if their contents give us any just conception 

 of the nature and the extent of the earliest fauna 

 and flora, the insignificant amount of modification 

 which can be demonstrated to have taken place in 

 any one group of animals, or plants, is quite in- 



