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 



FIG. 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- 



