290 DR. TRAQUAIR ON THE ASYMMETRY OF THE PLEURONECTIDA. 
tends forwards, and bridges over the upper eye before it has completed or even com- 
menced its turn. But, before a conclusive answer can be given to that question, much 
more extensive observations on Pleuronectidean embryology are necessary. 
Concluding Note. 
Since writing the foregoing Memoir, my attention has been drawn to a paper, on Steen- 
strup's views on the obliquity of Flounders, by Prof. Wyville Thomson, in the * Annals 
and Magazine of Natural History’ for the present month (May 1865). As far as can 
be gathered from the abstract of Prof. Steenstrup’s original paper, which Prof. Thomson 
has in the present communication afforded us, the learned Danish naturalist attempts 
no explanation on developmental principles of the singular “double” monstrosities 
oceurring in flatfishes, and also questions the accuracy of Van Beneden’s observations 
already quoted. In his critical remarks on this paper, Prof. Thomson has expressed the 
same views as to the morphological relations of the eyes to the two frontal bones, and as to 
the constitution of the pseudomesial beam or bar of the cranium, as those advocated in the 
preceding pages, though so far agreeing with M. Steenstrup as to consider that the 
“eye of the blind side actually passes from its own side of the head to the other side— 
at all events under the integuments and under the subeutaneous tissues, which contain 
the rudiments of the dermal bones forming the support of the anterior border of the 
dorsal fin, if not actually through the head itself." 
In justice, however, to myself I may be permitted to state that the Memoir just 
concluded is hardly altered from that which formed my Graduation Thesis at Edinburgh 
in 1862, and which may be consulted in the library of the University there, where it is 
deposited *. The same views were also expressed by me in a criticism of Prof. Steenstrup's 
paper in the * Annales, read by me before the Royal Physical Society of Edinburgh, on 
the 25th of January of the present year, and about to be published in the forthcoming 
part of its * Proceedings. 
* The Medical Faculty of the University of Edinburgh awarded a gold medal to this Thesis, Ist August, 1862. 
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