154 DARWINISM AND THE PROBLEMS OF LIFE 



the two " intermaxillary bones " in the child, and 

 showed that they fuse together in the adult, and 

 cannot be distinguished any longer from the other 

 two jaw-bones. 



It is the constant practice of natural selection to 

 build on actual material, and that is the quickest way 

 of accomplishing anything. Hence, when the amphibia 

 took to living on land, and needed support for the 

 body and organs of locomotion, the four fins of the 

 fish were converted into the limbs of the land animal. 

 In the lower fishes the joint of the jaws is formed of 

 two bones, which are replaced in the higher ones by 

 a greater development of the articulating bones. The 

 abandoned bones are found in the higher animals 

 only in the internal ear, where they still form a joint 

 as the "hammer" and the "anvil"; but instead of 

 mastication, it serves for conducting sound. 



We could show that nearly all the organs of the 

 vertebrates are found in all the five classes, and have 

 always the same fundamental form and structure. We 

 have seen in the previous chapter that Darwinism 

 explains these similarities, great and small, by the 

 law of heredity. The children of a certain couple of 

 human parents are more like each other than their 

 children will be — or brothers and sisters are more 

 like each other than cousins — and it is just the same 

 with animals. Birds are nearer to reptiles than to 

 amphibians, because if we look upon the actual 

 reptiles as brothers of the actual birds, the actual 

 amphibians will be their cousins. It was from reptiles 

 that the birds descended, and the ancestors of all 



