432 MB. E. w. L. HOLT — STUDIES IN [May 1, 



III. On an Aduxt Specimen oe the Common Sole {Solea vulgaris, 

 Quensel) with Symmetrical Etes, with a Discussion oe 



ITS BEAEING ON AmBICOLOEATION. 



The specimen forming the subject o£ this note was obtained in 

 the Grimsby Fish-market in the autumn of 1892. It was caught 

 in the North Sea, but on which particular fishing-ground I could 

 not find out, nor is the matter of great importance. 



It measui'es 15:^ inches in total length, the head is 2h inches 

 long, and the greatest height of the body is 5| inches. The total 

 length without the caudal fin is 13| inches. The specimen may 

 therefore be said to have the normal proportions of a Sole of that 

 length. It is a female, and it is apparent, from the condition of 

 the germinal epithelium and from the presence of a few ripe but 

 decomposing ova in the ovary duct, that it had spawned in the 

 preceding spriug or summer. 



Of the right or upper surface it may be sufficient to say that the 

 only point in ^^■hich it differs from a normal example is in the 

 absence of the upper or left eye. In the normal adult of this 

 species, as is well known, the upper eye is about an eye-length 

 above and about half a length in front of the lower or right eye, 

 occupying the front portion of an ovoidal depression, quite visible 

 in living fish and even more conspicuous in spirit preparations. 



In the example before us, the depression is present, but the eye 

 is wanting. The only other point, one which would not in itself 

 attract particular notice in an otherwise normal example, is that 

 the final curve of the dorsal cephalic branch of the lateral line is 

 rather less abrupt than usual. The scales being omitted in fig. A, 

 this structure is shown as a bold line, which, of course, it is not 

 in the actual condition. It will be understood that scales are 

 present wherever they are found in normal examples, extending 

 also over the site normally occupied by the upper eye. The dorsal 

 fin extends forward to the normal extent, and the number of its 

 rays, 87, is within the known limits of variation in normal 

 examples of the species. The pigment of the upper side is per- 

 fectly normal. 



Turning to the left or under surface, we find the divergence 

 from the normal type again practically limited to the eye. Amongst 

 minor points, the posterior opening of the nostril of this side is 

 very slightly in rear of its usual position, and a doA\nward curve 

 of the lateral line, which, starting at the same point as the dorsal 

 cephalic branch, passes, in some normal Soles now before me, in an 

 almost semicircular sweep to the posterior region of the mouth, 

 cannot be detected in the abnormal example. But as this struc- 

 ture, and also the dorsal branch, is altogether omitted in Cuoning- 

 ham's figure of the blind side \ it may be presumed that it is not 

 always noticeable even in normal specimens. A shght extension 

 of pigmented and scaled skin on to the under surface of the head 

 (fig. B) below the mouth is due, as I suppose, simply to the action 

 ^ ' A Treatise on the Common Sole,' Plymouth, 1890, pi. v. 



