294 THE EVOLUTION OF MAN. 



in comparing the several component bones with the separate 

 parts of vertebrae ; they supposed that in this way they 

 could prove that the developed mammalian skull consists 

 of from three to six original vertebrae. The hindmost of 

 these skull -vertebras was, according to them, the occipital 

 bone. A second and a third vertebra were represented by 

 the sphenoid bone, with the parietal bones, and by the 

 frontal bone, etc. The elements of anterior skull vertebrae 

 were even supposed to exist in the face bones. In opposi- 

 tion to this view, Huxley first called attention to the fact 

 that in the embryo this bony skull originally develops 

 from a simple cartilaginous vesicle, and that in this simple 

 cartilaginous " primitive skull " not the slightest trace of a 

 constitution of vertebrate parts is visible. This is equally 

 true of the skulls of the lowest and most ancient Skulled 

 Animals (Craniota), the Cyclostomi and the Selachii. In 

 these the skull retains throughout life the form of a simple 

 cartilaginous capsule of an inarticulate " primitive or 

 primordial skull." If the older skull-theory, as it was 

 accepted from Goethe and Oken by most comparative 

 anatomists, were correct, then in these lowest Skulled 

 Animals especially, and in the embryos of the higher Skulled 

 Animals, the constitution of the " primitive skull " by a 

 series of " skull-vertebrae " would be very clearly evident. 



This simple and obvious consideration, first duly em- 

 phasized by Huxley, indeed overturns the famous " Verte- 

 brate Theory of the Skull," as held by the older comparative 

 anatomists. Yet the entirely correct fundamental idea 

 holds good, i.e., the hypothesis that the skull develops from 

 the anterior portion of the spinal column by differentiation 

 and peculiar modification, just as the brain develops from 



