216 Proceedings of the Royal Physical Society. 



eyes has passed bodily through the head, beneath the dorsal 

 fin, till it has reached that side where both are now found, 

 and where it has formed for itself a new and anomalous 

 orbit ; a view which, it must be confessed, grates a little 

 against most of our preconceived morphological ideas. 



But from what we see on the outside of the fish, we can 

 only rashly speculate. It is only by anatomical and embryo- 

 logical research that we can gain an insight into the true 

 state of the case. 



As I am looking forwards at no' distant date, to the pub- 

 lication, elsewhere,* of a detailed account of the osteology of 

 the flat-fish head, considered in relation to the asymmetry 

 of these fishes, 1 will, in this communication, content my- 

 self with a brief review of the theories which have occurred 

 to various writers on this subject. And especially I shall 

 inquire as to what light embryology, including the exami- 

 nation of monstrosities, has as yet afforded us. 



Autenrieth is the oldest writer I have found to allude to 

 the subject anatomically, in a paper on the anatomy of the 

 Plaice {Platessa vulgaris), published in the year 1800. f His 

 remarks on the osteology of the Plaice are however meagre, 

 and his theoretical conclusions will seem to us now-a-days 

 absurd ; for he accounts in the following manner for the 

 position of both eyes on the right side of the head. He says, 

 " The examination of the skeleton shows us that the entire 

 left side of the fore part of the cranium is in reality want- 

 ing, and that nature, in order not to lose an eye, was necessi- 

 tated to put it into the hollow of the right cheek, under the 

 alone remaining right orbit." 



Eosenthal (Ichthyotomische Tafeln, Berlin, 1812-22), a 

 little more rational in his ideas than Autenreith, held the 

 upper eye of the flounder to be that of the left, or now eye- 

 less side, but accounted for its getting to the right side by 

 its being thrust through the head and getting placed be- 



* Transactions of Linnean Society for 1865. 



f Wiedemann's Archiv fur Zoologie und Zootomie. Thl. i. 1800, s. 47, et 

 seq. " Bernerkungen iiber den Bau der Scholle (Pleuronectes platessa) ins- 

 besonders und den Bau der Fische hauptsachlich ihres Skelets im Algenieinen," 

 Von Dr T. H. F. Autenrieth, Prof, der Anatomie in Tubingen. 



! 



