1894.] TBLEOSTEAN MOEPHOLOGT. 441 



Plaice rebut such a supposition, while no evidence is forthcoming 

 in its favour. The same authority has also failed to detect any 

 difference in the habits of partially ambicolorate but structurally 

 normal fish. Plaice and Flounders, more or less coloured on the 

 imderside, are extremely common in the Humber, and having kept a 

 considerable number of such fish in the Cleethorpes tanks and 

 watched their behaviour attentively, my own experience is precisely 

 to the same effect as Cuuniugham's. The young Brill, with the 

 hooked dorsal, structurally abnormal but not ambicolorate, differed 

 in its habits in no respect from several normal Brill of about the 

 same size, taken at the same place, and kept in the same tank. 



Of the habits of the Sole under discussion I have of course no 

 knowledge, the fact that it was trawled in company with a number 

 of normal examples being of httle value, since I have occasionally 

 trawled such essentially pelagic fish as Mackerel and Herrings. 

 The complete asymmetry of everything but the eyes seems, 

 however, to refute the idea that it could possibly have maintained 

 a vertical position, and the complete absence of pigment from the 

 blind side of the head and ti'unk would seem, in the light of 

 Cunningham's investigations, to show that that side could not have 

 been exposed to the light, unless the susceptibility of the individual 

 were so slight that the power of pigment-production was practically 

 lost by the derma of that side. 



The bearing that the condition of our specimen has upon the 

 question of ambicoloration,into which I have entered at so great a 

 length above, appears to me to be this, — that the phenomenon of 

 complete ambicoloration, as typified by some Cyclopean Pleuro- 

 nectids, cannot be held to depend on the mere arrest of the 

 migration of the eye, unaccompanied by other structural abnor- 

 mality \ The proposition, as laid down by Cunningham and 

 MacMunn, that complete ambicoloration occurs only in Cyclopean 

 examples, is in no way affected thereby, but, as it seems reasonable 

 to suppose that any abnormality of habit (whether in the pelagic 

 or later stages), such as Giard ^ considers to exist in Cyclopean 

 Turbot, would surely be intensified in a specimen like that now 

 before us, I should say that the theory of the French observer may 

 be considered to be finally disposed of. 



Anatomical Features. 



Most of my superficial and all my subdermal observations were 

 made after the specimen had been some months in alcohol. 



On removing the skin from the right (normally the ocular) side 



1 That ambicoloration may exist in a specimen not essentially differing in 

 external cliaracteristics from the Sole now under consideration is shown by a 

 young Turbot in the St. Andrews Museum, described and figured in the 

 'Fauna of St. Andrews Bay' by Professor Mcintosh. The specimen is only 

 a few inches in length and normally developed, except that the eyes are on 

 different sides of the head, and pigment exists on both sides of the body. 



2 " Pur la Persistance partielle de la Symetrie bilaterale chez un Turbot," 

 0. K. Soc. Biol. Jan. 22, 1892, p. 31, and Nat. Sci. i. 5, p. 358. 



