The Skull Ir 
and, from their rod-like jointed character, they look 
very much like the real gill-arches of a fish. The fourth 
arch vanishes. 
Such is the almost incredible alchemy which Nature 
has wrought from a plastic rod of gristle,—transforming 
it into beak, tongue, and ears. 
Z = Gimp 
Parx. 
Few of us, when watch- 
() 
iy 
_ ID 
MMi 
Fig. 89.—Ultimate distribution of the four embryonic gill-arches in the skull 
of the adult bird. The dotted portions are not developed. (Adapted from 
Newton.) Compare with Figs. 83 and 88. 
ing the gently waving gills of a fish, have realized how 
much we indirectly owe to them. A noted German 
anatomist—Ixarl Gegenbaur—believes that we owe even 
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. 
