304 NATURAL HISTORY. 



with the hind-limbs as well as the fore-limbs. Similarly 

 it would be concluded that the ancestral type of the 

 Ruminants possessed well-developed upper front teeth; 

 and that the snakes, though now footless, were descended 

 from some reptilian type in which the limbs were present. 

 Rudimentary organs, therefore, strongly support the view 

 that the different forms of animals have been produced by 

 modification from older and different forms. 



(5) Lastly, the known facts of Palaeontology offer the 

 strongest support to the general theory of the evolution of 

 animal forms from pre-existing species. Amongst extinct 

 species we are constantly meeting with types which stand 

 intermediate between groups otherwise more or less 

 remote. One of the most famous examples of this is 

 afforded by the fossil forms which link together the two 

 groups of the Reptiles and the Birds two classes of 

 animals* now so little resembling each other, that no one 

 save a naturalist would ever suspect a relationship 

 between them. Thus the past has yielded up to us the 

 remains of true reptiles (the Deinosaurs) which walked 

 upon their hind-legs, like birds; other reptiles (the 

 Pterodactyles) possessed the hollow bones and the power 

 of genuine flight characteristic of the living birds; some 

 genuine birds (the Odontornithes\ finally, resembled the 

 Crocodiles in having the jaws furnished with numerous 

 pointed conical teeth. Another famous example of the 

 intermediate forms which palaeontology has brought to 

 light is that afforded by the extinct horse-like Quadrupeds 

 of the Tertiary period. It is well known that our present 

 Horse is peculiar in having only a single fully-developed 

 toe on each foot. This toe corresponds with the middle 



