94 



ORGANIC EVOLUTION 



functional hind limbs possessed by the terrestrial ancestors 

 of the whales. Similarly, the Apteryx of New Zealand, 

 which has no functional wings, has vestiges of wings, recall- 

 ing the typical bird 

 condition (Plate 35). 

 All these vestigial 

 structures are with- 

 out much meaning 

 until we recognize 

 that they point us to 

 the ancestral forms in 

 which they were im- 

 portant functional 

 organs. We might 

 give many illustra- 

 tions of such vestigial organs. I will merely mention a few 

 found in man : the muscles which move the skin, but in 

 most persons are too weakly developed to do so except in 



FiG. 15. Part of the skeleton of a boa constrictor, 

 showing the vestigial bones of the hind limbs. From a 

 specimen in the United States National Museum. 



FlG. 16. Skeleton of Greenland whale, showing the vestigial pelvic bones near the base of 

 the tail. [From ROMANES, after FLOWER.] 



the region of the face; the muscles that should move the 

 ears but usually are not functional (Fig. 1 7) ; the nictitating 

 membrane, vestigial in man, but well developed as a third 

 eyelid in reptiles and birds (Plate 36); the hair of the body, 



