OUR BEST FEATURES 



pharynx. In the development of the human embryo we 

 see these three stages reproduced. 



EVOLUTION OF THE TONGUE AND 

 RELATED STRUCTURES 



In Amphioxus (Fig. 54) there is no tongue and 



in the lampreys and hags the so-called tongue 



with its enclosed cartilages probably represents 



the lower jaw of the shark (Stockard, Goodrich). 



In the shark the folding up of both the jaw 



cartilages and the gill cartilages causes the lower 



ends of the latter to project forward in a series of 



V's into the floor of the mouth (Fig. 7). These 



cartilages support the tongue proper, which at 



first is only a thickening of the floor of the mouth 



covered with epithelium containing the "taste" 



cells. In some of the amphibians the tongue 



becomes highly muscular and protrusile and by 



the time we reach the lower mammals the tongue 



is fundamentally the same as that of man. The 



early primates have a long narrow tongue with a 



well developed "under tongue" beneath it; in the 



higher primates, especially the orang, chimpanzee 



and gorilla, the tongue approaches the human type 



but is longer in proportion to its breadth. In the 



detailed number and arrangement of the papillae 



123 



