162 



LECTURE IX. 



ON THE STRUCTURE OF THE SKULL. 



THE SKULL OF THE PIKE COMPAEED STRUCTURALLY AND 

 DEVELOPMENTALLY WITH THAT OF MAN. 



In the series of animals possessing a bony skeleton, osseous 

 fishes and man mav be regarded as the extreme terms ; and 

 I now select the skull of an osseous fish — the Pike — for com- 

 parison with that of Man. Whatever community of structure 

 obtains between these must be expected to persist throughout 

 the intermediate terms ; while the differences between them 

 will be more or less completely bridged over by the subsequent 

 study of the skulls of the lower Mammals, Birds, Reptiles, and 

 Amphibians. 



At first sight, the skull of a pike (Fig. 65) presents the most 



Fig. 65. 

 S.Or 



I Oh, 

 At An SxjPr.O/x -Bra ' 



Fig. 65. — Side view of the skull of a Pike (after Agassiz). — Prf, prefrontal ; H.M., hyo- 

 mandibular bone; Op., operculum ; S.Op., sub-operculum ; I.Op, inter-operculum ; 

 Pr.Op, pre-operculum ; Brg., branchiostegal rays; Sy, symplectic; Mb, meta-ptery- 

 goid ; PI, palato-pterygoid arch ; Qu., quad rat um ; Ar, articular ; An, angular ; J9, 

 dentary ; S.Or., supra-orbital bone. 



