2 189 
In the absence of figures we find it difficult to follow 
Cunningham’s explanation, and we also find it difficult 
to believe that the same mechanical! strain—that of the 
oblique muscles between the left ectethmoid and the left 
optic bulb—could have, at the same time, (1) retated the 
bulb, (2) pressed on the interorbital septum so as to bend 
that over to the right, and (5) rotated the ectethmoid 
through a right angle. And we regard it as unjustifiable 
to base such a mechanical explanation on the attachments 
of the muscles in an already asymmetrical skull. It is 
inconceivable that the oblique muscles were attached in 
the immediate symmetrical ancestor of the sole in the 
same way 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 Cunningham’s hypothesis is an impos- 
sible one. Unlike the sole, all the oblique muscles are 
attached to the left prefrontal (=Cunningham’s left 
ectethmoid), and the latter we regard as the least altered 
element in the orbital or preorbital regions. ‘That the 
surface to which the oblique 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. 
