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Show 432 MR. E. W. L. HOLT-STUDIES I N [May 1, III. ON AN ADULT SPECIMEN OE THE COMMON SOLE (Solea vulgaris, Quensel) W I T H S Y M M E T R I C A L EYES, W I T H A DISCUSSION OE ITS B E A R I N G O N A M B I C O L O R A T I O N. The specimen forming the subject of 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 measures 15| inches in total length, the head is 2\ 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 spring or summer. Of the right or upper surface it m ay be sufficient to say that the only point in which 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 perfectly 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 downward 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 structure, and also the dorsal branch, is altogether omitted in Cunningham's figure of the blind side1, it may be presumed that it is not always noticeable even in normal specimens. A slight 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 1 ' A Treatise on the Common Sole,' Plymouth, 1890, pi. v. |