OUR FACE FROM FISH TO MAN 



Of the bones around the eye (Fig. 51), originally 

 five in number, three (the prefrontal, postfrontal, 

 postorbital) are eliminated by the time of the 

 earliest mammals, so that man inherits only two 

 of the original five, namely the lacrymal and the 

 jugal or malar. 



The temporo-mandibular series (Fig. 52), orig- 

 inally including eight bones (the intertemporal, 

 supratemporal, squamosal, quadrato- jugal, sur- 

 angular, angular postsplenial, splenial), suffers 

 gradual reduction, until in the earliest mammals, 

 as in man, only the squamosal remains, at least in 

 the lateral view of the skull. In the mammals the 

 squamosal has fused with the enlarged periotic 

 mass and in the anthropoids and man the tym- 

 panic is added, the whole complex forming the 

 temporal bone. 



At every successive stage of evolution advances 

 in skull structure were dependent upon improve- 

 ments in the brain itself, upon shiftings and 

 enlargements of the parts containing the sense 

 organs, upon modifications of the jaws and teeth, 

 accompanying or accompanied by changes of 

 habits. The skull in turn is closely integrated 



with both the active and the passive elements of 



88 



