200 ON THE STRUCTURE OF THE SKULL. 



of much controversy. In a remarkable essay published in the 

 first volume of the " Memoires du Museum," Cuvier proposed to 

 consider the upper dentigerous arch (h) as the homologue of the 

 palatine and pterygoid bones of osseous fishes, the cartilages 

 (i, k) as the premaxilla and maxilla. The suspensorium (g) he 

 considered to be the homologue of the hyomandibular, symplectic, 

 and metapterygoid. The lower dentigerous arch (Mn) was ob- 

 viously the mandible. 



On this latter point all anatomists are agreed ; but, in his 

 famous " Comparative Anatomy of the Myxinoid Fishes," 

 Johannes Miiller — guided, like Cuvier, by purely anatomical 

 considerations, and bv what I have elsewhere termed the 

 method of gradation — proposed a totally different interpretation 

 of the other parts. According to this view, i, h, and I are 

 merely labial cartilages, and therefore do not represent the pre- 

 maxilla and maxilla. Again, Cuvier had greatly relied upon 

 the absence of any parts on the inner side of h which could 

 answer to palatine or pterygoid elements, in arguing that h 

 itself represents them. But Miiller adduced his own and 

 llenle's observations to prove that in a great many Plagiostomes, 

 particularly the Bays, such cartilages, situated on the inner side 

 of the upper dentigerous arch, do occur, and thus arrived, by a 

 line of argumentation precisely as legitimate as that of Cuvier, 

 at the exactly opposite result, — that h represents the premaxilla 

 and maxilla, and not the palatine or pterygoid. 



The fact that these opposing view T s were entertained by men 

 -like Cuvier and Miiller is evidence that each had much in its 

 favour ; but, in truth, neither was free from grave difficulties. 

 Thus neither accounted for the articulation of the mandible 

 with the upper dentigerous arch, — a relation into which the 

 mandible never enters either with the palatine, or with the 

 maxilla, in the vertebrate series; and as Miiller himself is 

 forced to admit that some of the cartilages on the inner side 

 of the upper dentigerous arch are accessory, why should not all 



be so? 



This is just one of those cases in which the study of develop- 

 ment manifests its full importance, and decides, at once, problems 

 which, without it, might be the subjects of interminable discus- 



