287 



APPEISTDIX I 



LOCOMOTION OF BIKDS AND OF FISHES, 



We have little to say concerning the locomotion 

 of these classes of animals. It would seem to us 

 that, although the fins of a fish are added, appar- 

 ently somewhat in the manner of limbs, yet the 

 fundamental locomotive action of a true fish comes 

 from the tail, following the ophidian motions of the 

 back bone, and acting on the water as the blade of 

 a single oar does when worked at the stem of a 

 small boat in the motion called " scuUing." 



Birds, we should say, fly by alternately raising 

 and pressing down the front edges of their wings. 

 The first motion presents the wing as a plane in- 

 clined upward to the air in the front-rear direc- 

 tion. This is the outer bearing, and on this plane 

 they rise after the second motion, which is a down- 

 ward stroke of the anterior edge, answering toi;he 

 inner bearing. If the action of flying come fully 

 under our theory of locomotion, the second motion 

 should collect the feathers in a spring before its 

 discharge. 



