189 



In the absence of fiouie.s Ave tiiul it difficult to follow 

 Ciinnino'liam's explanation, and we also find it difficult 

 to believe that the same median ical strain — that of the 

 oblique niuscles betAveen the left ectethnioid and the left 

 optic bulb — could have, at the same time, (1) rotated the 

 bulb, (2) ]nessed on the interorbital septum so as to bend 

 that over to the rig-ht, and (■)) rotated the ectethnioid 

 throug'h a rig-ht angle. And we regard it as unjustifiable 

 to base such a mechanical explanation on the attachments 

 of the muscles /// an nlready (t.-^yunnetrical sh/U. It is 

 inconceivable that the obli(iue niuscles were attached in 

 the immediate symmetrical ancestor of the sole in the 

 same wav that they are now. In the Cod, for example, we 

 find them arising symmetrically from the interorbital 

 septum, and therefore any discussion of the possibility of 

 those muscles producing distortion of the head should be 

 based on the conditions present in an unmodified 

 symmetrical cranium. 



But whatever the conditions are in the sole we find 

 that in the Plaice Cunninghams hy])othesis is an impos- 

 sible one. Unlike the sole, all tht> ()bli(ine muscles are 

 attached to the left prefrontal (= Cunningham's left 

 ectethnioid), and the latter we regard as the least altered 

 element in the orbital or preorhital regions. That the 

 surface to which the ()bli(|ue muscles are attached now 

 looks upwards we regard as more simply explained by 

 supposing that the upper portion of the left prefrontal like 

 most of the left frontal, with which it was most probably 

 suturally attached, suffered abortion in the shifting of the 

 left eye. And the shifting of the origins of the oblique 

 muscles to it has been a result of, or has been concomi- 

 tantly brought about by, the approximation of the eyes, 

 and the increasing tendency to dorsal vision. 



