OF TIIE EARLIER VERTEBRATA. 65 



fcbe vertebrated animals, proves that the knowledge of such 

 M being as man existed before man appeared ; for the .Divine 

 Mind which planned the archetype also foreknew all its modi- 

 fications. The archetypal idea was manifested in the flesh, 

 under divers such modifications, upon this planet, long prior 

 to the existence of those animal species that actually exem- 

 plify it." 



But while we find place in that geological history in which 

 every character is an organism, for the " ideal exemplar" of 

 Professor Owen, we find no place in it for the vertebrae- 

 developed skull of Professor Oken. The true genealogy of the 

 head runs in an entirely difierent line. The nerves of the 

 cerebral senses did not, we find, originate cerebral vertebrae, 

 seeing that the heads of the first and second geologic periods 

 had their cerebral nerves, but not their cerebral vertebr83; and 

 that what are regarded as cerebral vertebrse appear for the 

 first time, not in the early fishes, but in the reptiles of the 

 Coal formation. That line of succession through the fish in- 

 dicated by the Continental assertor of the development hypo- 

 thesis, is a line cut oflt All the existing evidence conspires 

 to show that the placoid heads of the Silurian system were, 

 like the placoid heads of the recent period, mere cartilagi- 

 nous boxes j and that there existfed ganoidal heads, that to 

 the internal cartilaginous box added external plates of bone, 

 the homologues, apparently — so far at least as the merely 

 cuiicular could be representative of the endoskeletal — of the 

 opercular, maxillary, frontal, and occipital bones in the osse- 

 ous fishes of a long posterior period, — fishes that were not 

 ushered upon the scene until after the appearance of the reptile 

 iu its highest forms, and of even the marsupial quadruped. 



