481 



Chapter X. 



VERTRBRATA CAPABLE OF FLYING. 



§ 1. Vertehrata ivitliout Feathers^ formed for flying. 



Few problems in mechanic art present greater 

 practical difficulties than that of raising from the 

 ground, and of sustaining and moving rapidly 

 through the air an animal body, composed as it 

 must be of many ponderous organs, which are re- 

 quisite for the performance of the higher functions 

 of life; yet Nature has achieved all this, not only 

 in endless tribes of the more diminutive inverte- 

 brate animals, but also in the more solid and mas- 

 sive organizations which are modelled on the ver- 

 tebrate type. These objects have been accom- 

 plished, in all cases, without the employment of 

 any other than the ordinary elements of those orga- 

 nizations ; modified, indeed, to suit the particular 

 purpose in view ; but yet essentially the same, 

 and regulated by the same laws of developement 

 which prevail throughout the whole animal system. 

 The adaptation of these elements to the construc- 

 tion of an apparatus of so refined a nature, as that 

 which is required for flying, implies the deepest 

 foresight, the most extensive plan, and the most 

 artificial combination of means. The foundations 

 for these peculiar forms of mechanism are laid in 

 the primeval constitution of the embryo ; and a 

 long and curious series of preparatory changes 

 take place before the completion of the finished 



VOL. 1. II 



