is 95 . THE HABITS OF ARCIIJEOPTERYX. 185 



muscular movements as are involved in flight itself. While in 

 all powerful fliers, both birds and insects, every movement of the 

 wing insures a change of the air in the respiratory organ itself (and 

 not merely in the passages leading to that organ), the form and 

 structure of Archaopteryx forbid us to believe that such an adaptation 

 existed in it. 



Conclusions as to the size and efficiency of the heart might be 

 drawn, but they are not only obvious but also perhaps a little risky ; 

 so I will leave them. 



Nobody, except the constructors of flying-machines, seems to be 

 ignorant of the fact that all powerful fliers have a wing-area which is 

 very large in proportion to the area of the immoveable aeroplanes. 

 Birds do not nowadays rely upon immoveable aeroplanes at all. The 

 wings serve all the functions of both propulsion and sustentation, and 

 the tail when used at all is used only for steering ; while the 

 vastly superior flight of insects is effected in the absence of any 

 special steering apparatus, the wings themselves serving alike for 

 propulsion, sustentation, and steering. 



In Archceoptevyx, then, we find an animal as yet not evolved beyond 

 the aeroplane phase of flight ; a phase characterised by the use of 

 large aeroplanes, which, while offering considerable resistance to 

 flight, take no part in the propulsion. It may further be pointed 

 out that among flying things, whether birds, mammals, insects, or 

 flying machines, the most efficient are all far broader from side to 

 side than they are long. Lilienthal, alone among men who seek to 

 fly, seems to have appreciated the real bearing of this fact. The 

 further mechanical consideration of the point, even as applied to 

 Archceoptevyx, would, however, take us too far. It is sufficient for my 

 present purpose to have pointed out wide differences of structure both 

 as to the immediate organs of flight and also as to the propelling 

 muscles and the respiratory organs on which powerful flight depends, 

 between, on the one hand, Avchceopteryx, and, on the other hand, all 

 other flying animals. I will only add an argument for the benefit of 

 biologists who may be unable to grasp the significance of mechanical 

 considerations. The oldest known bird — Arcluzoptevyx — was con- 

 structed, so far as the sustentatory apparatus of flight was con- 

 cerned, on a principle which has been superseded in all modern birds, 

 and which may therefore be safely pronounced, even on purely 

 biological grounds, to be inferior in effectiveness to the principle of 

 construction which has superseded it. 



A vchceoptcryx was, therefore, not a very good flier. How good it 

 was as a flier, I dare not guess ; though the perfect, but all too 

 small, wings strongly suggest that, in spite of the impediments I 

 have mentioned (free digits, heavy head and neck, large aeroplanes 

 offering resistance to rapid movement, small muscles, heavy non- 

 pneumatic bones, and deficient respiratory apparatus), Avchwoptevyx 

 could fly better than the competing pterodactyles. 



