THE THEORY OF THE VERTEBRATE SKULL. 303 



These questions must be answered before the theory of the 

 lower arches of the skull can be placed upon as satisfactory a 

 footing as that of the upper arches ; and they can be answered 

 only by the embryologist, who may be encouraged to the 

 difficult task by reflecting on what he has done already ; though 

 keeping in view the adage of the Roman, and 



" Nil actum reputans si quid supercsset agendum." 



