84 THE TRANSFORMATIONS OF THE ANIMAL WORLD 



the Batrachians, we must come down to more 

 generalized and earlier forms, such as the Dipneusta. 

 In the same way we could not derive the Mammals 

 from any type of existing reptiles, and must go 

 back to the Permian to discover their origin in the 

 Theromorphs. From the point of view of prophetic 

 resemblances, these animals are inferior to the modern 

 Reptiles, and recall some of the early stages of the 

 Reptiles, as well as of the Mammals. In the group of 

 Mammals, the Apes could not have descended from 

 the Carnivora nor from the Ungulates and recipro- 

 cally, and we can only trace their slender affinities 

 back to the Bunodont types of the lower Eocene. 

 Finally, the various groups of Ungulates must all be 

 attached to the hardly specialized group of Ambly- 

 pods, with their poorly developed brain and their 

 plantigrade foot with its five toes. It is easy to 

 understand that the generality and the plasticity 

 of all these forms is the reason of the existence of 

 their ancestral relations. 



It is this inferiority, arising from a too-advanced 

 specialization, which enables us to understand the 

 extinction of forms, the most powerful of any from 

 their size and from their perfected natural weapons. 

 Accustomed to live in luxurious indolence, these 

 immense beasts could neither bear the diminution 

 of their food nor the other changes of the en- 

 vironment. It is a well-established fact that none 

 of the large types of terrestrial animals has been 

 able to maintain for long its supremacy in the 

 course of the geological ages. All the groups of 

 the Carnivora, of the Ungulates and of the Quadrumana 

 known in detail, commence with types small in size 



