The Skull 



I I 



5 



and, from their rod-like jointed diaraeter, they look 

 A-ery inueh like the real gill-arches of a fish, 'i'lie fourth 

 arch vanishes. 



Such is the almost incredil)le alclieniy which Nature 

 has wrought from a plastic rod of gristle, — transforming 

 it mto beak, tongue, and ears, lew of us, when waidi- 



FiG. 89. — ritimate distrilnition of tlie four embryonic gill-arclios in tlie skull 

 of the adult bird. The dotted portions are not dc\eloi)ed. (.\dapted from 

 Newton.) Compare with Figs. S.'i and S8. 



ing the gently waving gills of a fish, have realized how 

 much we indirectly owe to them. A noted (lernian 

 anatomist — Karl Gegenljaur — believes that we owe e\-eri 

 our hands and arms (by way of the pectoral fins of fishes) 

 to portions of the gill framework, but this theory is not 

 generally accepted. 



