96 THE TRANSFORMATIONS OF THE ANIMAL WOLRD 



be denied that, taken in its entirety, the palaaonto- 

 logical evolution represents a gradual improvement 

 from the Primary epoch down to our own day. 

 We shall, however, have to return to this point, 

 and to show that recent discoveries, by pushing 

 further and further back in time the first appear- 

 ance of the highest groups in the animal series, 

 tend to diminish little by little the evidence of this 

 principle, and to cut out one by one the proofs of 

 it until now deemed the most demonstrative. 



Another philosophical idea which crops up at 

 intervals in the works of Gaudry relates to the stages 

 of evolution of fossil animals and to the use that can 

 be made of these stages to determine the ages of 

 the strata containing their remains. This point of 

 view is only, after all, a sort of direct corollary of 

 the idea of the continuous progress of beings. 



" If palaeontology enables us to assist at a regular 

 evolution of the animated world, it is evident that 

 the stage of development of fossils must correspond 

 to their geological age ; we then understand why such 

 and such fossils are met with at such and such 

 levels. The geologists who bring to us the bones of 

 Vertebrates that we may declare the age of the soil 

 in which they were discovered, are aware that our 

 first care is not to inquire whether they are any of 

 the numerous known species, but that we seek to 

 determine to what stage of evolution they belong, 

 because the stages of evolution which mark the 

 changes in organization, at the same time mark 

 the principal divisions of geological times. Here are 

 two different deposits ; I note that the animals in 

 the one indicate a less advanced stage of evolution 



