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with the ethmoidal cartilage, and practically they arise 
from the lower portions of the median frontal ridges. 
Now if we suppose that the asymmetrical skull of the 
Plaice first began to appear in an ancestral form 
resembling the Cod, grave difficulties at once arise. For 
if a rotation from left to right of the orbital region of such 
a cranium took place, it is evident that although the left 
eye might ultimately look upwards, the right on the other 
hand must also move and would tend to become buried 
in the tissues of the head. Moreover it is probable that if 
a round fish such as the Cod adopted sedentary habits on 
the sea bottom, the flattening, if it occurred at all, would 
be a dorso-ventral one, as in the case of the skate. 
But if we assume that a laterally compressed fish (like 
Zeus, for instance) took to a bottom habit, and began to 
lie on one side of its body, the changes necessary to bring 
about such asymmetry as we find in the Plaice would be 
much less violent. In such a form we may suppose that, 
following the lateral compression of the body, the eyes 
would have moved to near the dorsal edge of the head, 
whilst the frontals would have become greatly compressed 
from side to side and probably elongated dorso-ventrally, 
like the right frontal of the Plaice. The eyes therefore 
being now close together near the dorsal median line of 
the head, require to travel so much the lesser distance. 
Now when such a fish assumed a bottom living habit, 
lying on (say) the left side of its body, any variations in 
the position of the left eye bringing it nearer the middle 
line than the right (v.e., nearer the upper side) would be 
of great advantage. This approximation to the middle 
line would be attained either by the attenuation of the left 
frontal or by a shifting of both frontals towards the right 
side. In the skull of the Plaice both these things have 
happened. 
