THE EVOLUTION OF THE BIRD 



tions under which soaring flight is possible, and those avia- 

 tors who have flown engineless aeroplanes (gliders) for 

 hours at a time have been copying the eagles and giving us 

 valuable information about the difficulties of the process, the 

 chief of which is perhaps the recognition of the upward- 

 directed currents of air on which it depends. 



The other difficulty, the inability of the aeroplane to fly 

 very fast or very slowly, depends on the long tail that all 

 present-day aeroplanes have. As soon as it becomes possible 

 to control an aeroplane that has no tail, or a very short one, 

 man may be able to copy the manoeuvers of the eagles. From 

 this point of view Archaeopteryx corresponds to a present- 

 day aeroplane, the modern birds to the aeroplane of the 

 future. It is certain that Archaeopteryx was clumsy, incap- 

 able of hovering over one spot and of alighting on a definite 

 perch. 



Archaeopteryx was therefore far inferior to the modern 

 birds (see fig. 3) in its power of flight. It was clumsy, ill 

 constructed, and lacked that perfection of form and motion 

 which makes the sea gull a constant source of delight. Is it 

 credible that a bird that was miraculously created in a 

 moment should be so imperfect? Is not the imperfection of 

 its machinery an evidence of evolution? Is it not more rea- 

 sonable to recognize in Archaeopteryx a necessary stage in 

 the long process by which a crawling reptile was gradually 

 converted into the perfect flying bird of to-day? 



I have here tried to bring together facts about the birds 

 that bear witness to their evolution from more primitive 

 ancestors. Comparative anatomy, embryology, and palaeon- 

 tology unite in telling the same story. They agree in testify- 

 ing that the bird is to-day a highly specialized descendant of 

 some reptilian ancestor. Is it at all probable that there has 

 been collusion among these witnesses and that their testi- 



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