Evolution 



that were functional in the past history of their possessors' race. 

 The appendix of man, for instance, is not only useless, but is 

 frequently a source of danger. But its presence is readily ex- 

 plained by supposing that it represents the bhnd-gut, which is 

 large and functional in many of the lower animals. Again, how 

 should we account for the presence of small functionless wing- 

 bones in the cassowary, unless by supposing that its ancestors 

 were accustomed to fly like ordinary birds ? How should we 

 explain the bones which represent the hind limbs of the whale, 

 unless by regarding the whale as descended from an animal 

 which had functional hind limbs, or the representatives of eyes 

 in animals that live in the dark, unless by supposing that these 

 are descended from ancestors which saw ? It has been well said 

 that the bodies of many animals are veritable antiquarian museums, 

 filled with relics of their own ancestors. 



The next argument for Evolution to which we would refer is 

 based on the similar structure and origin of organs or members 

 that have entirely different uses. In Fig. ii are figured the bones 

 of the fore limbs of four different mammals, a whale, a bat, a 

 dog, and man. The first is used for swimming, the second for 

 flight, the third for locomotion on land, and the fourth as a grasp- 

 ing and holding organ. If these organs had been specially de- 

 signed, each for its specific purpose, we should expect to find 

 fundamental differences in structure. Actually the general 

 arrangement of bones is the same in each case. A fact 

 like this points strongly to a common origin of the four types 

 mentioned, and to a general primitive arrangement of the bones 

 of the limb. This primary type, it seems natural to suppose, has 

 been modified for various special purposes in many different 

 directions, the general features remaining recognisable. Many 

 other cases of homology, or similarity of structure and origin, 

 in organs whose function is dissimilar, might be quoted. Thus 

 the poison gland of the poison snakes is not an organ which has 

 been specially developed, but is a modified portion of one of the 

 salivary glands. The hoof of the horse and the finger nail of man 

 can evidently be satisfactorily explained as modifications of a 



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