THEORY OF EVOLUTION 25 



in exactly the same sense as is the evidence from 

 comjjarative anatomy. It suffices to know that 

 there hved in the past a i^articular "grouj)" of 

 animals that had many points in common with 

 those that preceded them and with those that 

 came later. Whether these are tlie actual an- 

 cestors or not does not so much matter, for the 

 view that from sucli a grouj) of species the later 

 species have been derived is far more probable 

 than any other view that has been proposed. 



With this unrivalled material and splendid 

 series of gradations, paleontology has con- 



I structed many stages in the past history of the 

 globe. But paleontologists liave sometimes 



, gone beyond this descriptive i)hase of the sub- 

 ject and have attempted to fornnilate the 

 "causes", "laws" and "principles" tliat liave led 

 to the development of their series. It has even 

 been claimed that paleontologists ai'e in an in- 

 comparably better position than zoijlogists to 

 discover such principles, because they know 

 both the beginning and tlie end of the evolu- 

 tionary series. The retort is obvious. In his 

 sweeping and poetic vision the paleontologist 

 may fail completely to find out tlie nature of 



