1894.] NATURAL SCIENCES OF PHILADELPHIA. 51 



the different parts of which must exist in all vertebrata, than for 

 believing that there is an archetypal vertebra and that the skull 

 must consist of several of the same, at least in a Goethe-Oken sense. 



It does not follow, however, because a difference of opinion may 

 prevail among morphologists as to the special homologies of certain 

 of the bones of the head that there sliould be any question as to the 

 truth of the general doctrine of the unity of organization of the skull, 

 so firmly established by Cuvier and others. 



On the supposition that the higher vertebrata have descended from 

 the lower, it is to be expected that the general structure of the 

 skull should be the same in both, the fundamental characters of the 

 skull of the former having been acquired by inheritance from that 

 of the latter. On the other hand, the skull should present greater or 

 less modifications according to the special nature of the different 

 vertebrata, such modifications being induced by the causes of varia- 

 tion incidental to different kinds of life. 



The skull, like the organism in general, is not made according to 

 a Platonic idea or pattern, but grows, its characters lieing acquired 

 by inheritance as modified by variation. 



