PALEONTOLOGY 139 



tain amount of change, what conclusions can be legit- 

 imately drawn from these facts? From the early 

 Eocene to the present from thirty-five to forty thou- 

 sand feet of sedimentary rocks have been deposited. 

 In this immense time the horse has lost two or three 

 toes, has increased in size, and his teeth and bones 

 have undergone no fundamental changes. 



Are we to conclude from this that the great Zeug- 

 lodon, a whale 70 feet long, was evolved during the 

 Cretaceous, in which its remains are not found, from 

 the small marsupials of that period — or that the 

 Quadrumana, the highest order of mammals next to 

 man, and the numerous large and highly-developed 

 and differentiated mammals of the Eocene were 

 evolved from the same small marsupials, of which 

 there is no evidence from fossils whatever? or, going 

 backward in time, shall we from the case of the 

 horse conclude that the first mammals were evolved 

 from reptiles, and that the first fishes were evolved 

 from worms? It is possible that the horse might, in 

 his long history, have undergone the changes claimed, 

 which are not very great comparatively — not funda- 

 mental, and that from this we might not legitimately 

 conclude that an invertebrate has become a verte- 

 brate, or that a reptile has become a mammal. 



In my opinion it is not true that every change of 

 structure is to be regarded as a proof of the general 

 theory of evolution. It may be granted that certain 

 changes have taken place in organic forms by way of 

 evolution without thereby admitting that all the great 

 and fundamental differences between organic beings 

 have thus been produced. 



I have in another chapter endeavored to show the 

 impossibility of satisfactorily accounting for the evo- 

 lution of various classes and orders of animals. 



Looking a't the known geological facts, there exist 



