188 NORTH SHA INVESTIGATIONS. 
to that which I have demonstrated in the case of the recessus ; and 
very probably this structure, which I suspect to be no more than a 
specialised portion of the membranous wall, not homologous with any 
known visual organ in higher animals, may prove to have a wider 
distribution than is at present known to us. 
V. On an Anvutt Specimen or THE Common SoLE witH SYMMETRICAL 
Hyes, with A Discussion or 1Ts Breartna ON AMBICOLORATION. 
Under the above title a detailed description of the specimen in 
question was communicated to the Zoological Society at a recent 
meeting. The fish is a female 15 inches long, differing from a 
normal specimen in no external feature of note except that the left 
(normally the upper) eye is nearly opposite to the right. The eye 
is partially withdrawn below the skin, and its vision doubtless must 
have been to some extent further impeded by the sensory filaments, 
which extend right up to the periphery of the cornea. Still, with- 
out doubt, the fish could see reasonably well with this eye. The 
left side is colourless, and the effect of the eye, which had the iris 
of the normal colour, peering out from the dead white surrounding 
region, was very striking in the fresh condition. On examining the 
skull it was found that the union of the left ectethmoid and sphe- 
notic into the “ pseudo-mesial process ” of Traquair had taken place 
as usual, and had taken on its usual fibrous connection with the 
large ligament bone which underlies the interneural spines of the 
anterior part of the dorsal fin. The abnormality of the skull was, 
in fact, limited to a slightly less development of the left ectethmoid, 
especially of its anterior spur, and the greater size of the very vari- 
able foramen which exists between the pseudo-mesial process and the . 
parasphenoid. This foramen normally gives exit to a cranial nerve, 
and puts the left recessus orbitalis into communication with the left 
(or upper) orbital cavity ; but in the specimen before us it is tra- 
versed by the muscles and the optic nerve of the left eye. The 
muscles have precisely their normal attachment, and the left ect- 
ethmoid has undergone the normal rotation, The eye rests internally 
against the pseudo-mesial process, and the general arrangement of 
the parts suggests that it has been drawn by the rotation of the 
attachment of the oblique muscles as far inwards ag the interposition 
as the pseudo-mesial process has permitted it to go. 
The question of ambicoloration is dealt with at some length in the 
paper, but the exigencies of space only permit me to notice a few 
points. In the first place it is evident that the occurrence of a 
normally coloured flat-fish with practically symmetrical eyes renders 
it evident that there is no necessary connection between the ambi- 
