104 The Bird 
gested. The poet Goethe thought the skull was merely 
a continuation of the neck-bones, very much expanded 
and changed, and although the division of the skull into 
three roughly outlined rings is possible, yet we have no 
direct proof of the truth of this theory. 
Fortunately, in the skulls of most animals, the bones 
are separate, and by keeping in mind the constancy of 
their position, the puzzle of the skull of a chicken begins 
to clear up. 
Just as the first back-bone was a gelatinous or gristly 
Fie. 80.—Cranium of Dogfish, cartilaginous, generalized in structure. 
one, so the old type of skull was entirely gristly or car- 
tilaginous. Sometimes on the seashore near the huts of 
the fishermen, we may pick up a strange-looking object— 
translucent and looking as if it were made of hard white 
rubber. Clinging to it is perhaps a long string of delicate 
beads of the same substance. This is the skull and back- 
bone of a dogfish or shark, and although the skull is 
very unlike the chicken’s cranium, yet many of the parts 
in the latter are faintly foreshadowed in the cartilage 
skull washed up by the waves. 
Through all the long ages of geological epochs, myri- 
