OUR BEST FEATURES 



the locomotor apparatus, a topic which will be 

 developed elsewhere. 



To each of the stages described above man owes 

 certain "basic patents," or adaptive improve- 

 ments which have been of critical importance in 

 his survival. Thus to certain far-off Devonian 

 air-breathing fishes man owes the general ground- 

 plan of the vertebrate skull, the combination of 

 primary "gill-arch" jaws with sheathing or outer 

 jaws, and each and every one of the twenty-eight 

 normal skull bones which he still retains. 



Next, he is indebted to the first amphibians for 



partially solving the innumerable problems caused 



by emergence from the water. These old pioneers 



cast off the whole series of bones that covered the 



branchial chamber and made for themselves an 



ear-drum out of the skin around the notch where 



the opercular was formerly located. The early 



reptiles safeguarded most of the inheritance from 



their semi-aquatic ancestors, dropping only the 



inter- and supra temporals. To the first of the 



mammal-like series man owes the beginnings of 



his temporal fossa and zygomatic arch, and the 



dominance of the superior maxilla. From the 



higher mammal-like reptiles he has inherited the 



89 



