44 EVOLUTION 



of Owen, to whom it owes its classic state- 

 ment : 



(1) The wing of a bird and the arm of a 

 man; they are both fore-limbs, with funda- 

 mentally the same structure as regards bones - 

 and muscles, nerves and blood-vessels; they 

 are homologous, but not analogous. 



(2) The wing of a bird and the wing of a 

 butterfly; they are both organs of true flight, 

 but they have no structural or developmental 

 resemblance ; they are analogous, but not 

 homologous. 



(3) The wing of a bird and the wing of 

 a bat; they are both fore-limbs of similar 

 jBtructure and development; they are both 

 organs of true flight ; they are at once homo- 

 logous and analogous. 



Now, the evolutionary suggestiveness of 

 homologies is indisputable. If we take, for 

 instance, a series of fore-limbs among back- 

 boned animals the arm of a frog, the paddle 

 of a turtle, the wing of a bird, the fore-leg of 

 a horse, the flipper of a whale, the wing of a 

 bat, and the arm of man we find detailed 

 homology not only as regards the bones, but 

 as regards muscles, nerves, and blood-vessels. 

 Throughout there is close similarity in the 

 fundamental material and in the mode of 

 origin, but the final results how different I 



