A PECULIARLY ABNORMAL SPECIMEN OF THE TURBOT. 45 



it, form a projecting hook-like process over the dorsal eye, that is, the 

 originally left eye which has moved to the right side of the head. This 

 projection, due to the absence of attachment between the base of the fin 

 at the anterior end and the head, occnrs commonly in ambicolorate 

 specimens of the turbot, and less frequently in ambicolorate specimens 

 of other species of Pleuronectidae. (See Cunningham & MacMunn, 

 " Coloration of Skins of Fishes," etc., Phil. Trans., 1894.) 



The specimen was caught by Miss Fox on September 28th last year, 

 on the sands at Polzeth, near the Doom Bar, Padstow, and was kept alive 

 in captivity till November 28th, when it died. When the fish was alive 

 the right side, on which the eyes are situated, was of course the upper 

 side, while the left was in contact with the ground. It presented, 

 therefore, the extraordinary case of a fiat-fish having its upper side 

 white and its lower side coloured. Several normal specimens were seen 

 with the abnormal one, and some were caught ; one of these was sent 

 with the abnormal specimen for comparison. The normal specimen was 

 4*2 cm. long ; its metamorphosis was complete, but there were still a few 

 scattered black chromatophores on its right or lower side. Similar 

 chromatophores are present on the right or upper side of the abnormal 

 specimen, and they are a little larger and more numerous. Miss Fox, 

 in a letter, stated that the upper side of this specimen was becoming 

 pigmented during the time she kept it alive, but it is evident that ex- 

 posure of this side to light had produced very little effect up to the 

 time of death. However, it is not impossible that, had the fish lived to 

 become adult, its upper side would have become completely coloured in 

 consequence of exposure to light, since I have proved by my experiments 

 on flounders that light produces pigment on the lov/er side of normal flat- 

 fishes. In that case the specimen would have been quite similar to the 

 ambicolorate turbot, or specimens coloured on both sides, which have 

 long been known, except that the present specimen would still be 

 reversed. 



The appearance of the two sides of the fish is shown in the two 

 figures here given, which are reproduced from photographs taken by 

 my friend Mr. E. T. Browne, of University College, London. I have 

 discussed the condition of the fish at greater length in a paper 

 in the ProceediiKjs of the Zoological Society, 1907, p. 174. I have 

 there pointed out that the condition, which is certainly congenital, is 

 that of a turbot of which the head is reversed while the body remains 

 normal. In other words, the fish consists of a reversed head joined to 

 a normal body. The abnormal position of parts in the fish must be 

 regarded as due to the abnormal position of corresponding parts in the 

 ovum from which it was developed. The determinants of the left side 

 of the head were on the right, and vice versa. I have suggested that 



