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Show 1894.] PROP. HOWES ON SYNOSTOSIS IN FISHES. 95 1. On Synostosis and Curvature of the Spine in Fishes, with especial reference to the Sole. By G. B. H O W E S , F.L.S., F.Z.S., Assistant Professor of Zoology, R. Coll. Sci. Lond. [Eeceived January 16, 1894.] (Plate XII.) A short time ago my pupil Mr. W. L. S. Loat placed in my hauds for examination a backbone of the Sole (Plate XII. figs. 1 a and 1 o) which presents the unique abnormality of a quinque-recurrent curvature, such as I believe has never before been recorded. On turning to that rich storehouse of teratological material, theEoyal College of Surgeons' Museum, for specimens which might throw light upon this extraordinary backbone, I have been so fortunate as to meet with facts which, while they show the Sole's vertebral column to be liable to a wide range of structural aberration, give us a clue to at any rate the determining cause of that form of curvature herein dealt with (cf. infra, p. 100) \ By a fortunate coincidence, two malformed backbones of this fish (figs. 4 a and 5) had been quite recently presented to that Institution by Prof. Bland Sutton; and to that gentleman, together with the Council of the College and my ever willing friend Prof. Chas. Stewart, I tender my thanks for permission to examine and report upon their specimens. Mr. Loafs specimen was that of an old fish having an estimated length of from 9 to 10 inches, and 47 of its vertebrae were preserved, the terminal ones (? 3 in number) having been lost. The backbone of the normal Sole is straight, except for a feeble arching of its anterior 14-16 vertebra?a. In this example (fig. 1 a) it was, as already stated, thrown into a series of fixed sinuosities, five in number as reckoned by their vertices, a marked depression preceding the terminal one. All the vertebrae but the anterior 3 or 4 and that lying at the base of the second dip were more or less displaced in the vertical plane, and the minor details of the disturbance may be more readily gleaned from the accompaning figure (which is an accurate copy of a photograph) than expressed in words. There can be no doubt that the aberration was congenital, for the vertebral bodies (which were fully formed and independent throughout) conform in many cases to sections of a circle, owing to the adaptive modification of their articular faces. More interesting, perhaps, than this is the condition of the arches, as is at once evident from the fact of the practical absence of any marked sinuosity of the contour described by their free ends. To 1 " The causes producing congenital curvature of the spine are unknown," R. Coll. Surgeons' Descr. Oat. of the Teratological Series, 1893, p. 94. 2 Cf. Cunningham, ' A Treatise an the Common Sole.' Plymouth : Marine Biol. Assoc, 1890. |