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Show 1906.] ON ABNORMAL TROUT EMBRYOS. 419 Fig. 1. Fig. 2. Fig. 3. Fig. 4. EXPLANATION OF PLATE XXXI. Cyclopean Trout of type A, seen from left side. Transverse section through frontal process of the same cyclopean Trout, showing the small approximated olfactory pits (O.) and the reduced olfactory capsular cartilage (C.). Transverse section through posterior part of cerebral lobes of same, showing the cerebral lobes (F.B.) intimately united along their inner surfaces, and the pineal body Pin. The central cavity of the brain (C.F.B.)is not dropsical, and the cerebral lobes are almost normal in size. Section passing through mid-brain, posterior part of eye, and mouth of same :- O.L. O.N. Pec. B. sup. B.inf. GL. Ch. Bet. Optic lobes. „ nerve. „ recess. Rectus superior. ,, inferior. Choroidal gland. Retina. M. T. C.So. Tr. Cr. PI. qt. Meek. L. Mouth. Tongue. Supra-orbital cartilages Trabecular crauii. Palato-quadrate. Symphysis of lower jaw Lymph space. Fig. 5. Section through mid-brain of embryo belonging to type B, showing obliteration of the ventral groove which should pass down into the stalk of the infundibulum. Fig. 6. Section through retina of eye described on page 446, showing failure of development of the optic nerve and of the choroidal fissure. Pg., pigment layer; Bet., retina; f., a few fibres, which do not, however, pierce the sclerotic. 4. Notes on Supernumerary Eyes, and Local Deficiency and Reduplication of the Notochord in Trout Embryos. By JAMES F. GEMMILL, M.A., M.D. [Received February 20, 1906.] (Plate XXXIII.*) (A) Supernumerary Eyes in Trout Embyros (two specimens). The first specimen is in some respects unique in vertebrate teratology. My attention was directed to it by the presence of an interruption or cleft in the right upper jaw, producing the appearance of a right-sided harelip in what seemed to be, in other respects, a normal newly-hatched Trout embryo. On cutting serial sections, I found that a small additional eye lay at the bottom of this cleft, in the roof of the mouth, to the right side of the middle line, in the same transverse plane as the normal eyes. The additional eye is embedded in confused muscular tissue, has a well-developed lens, a small retina, no choroidal fissure and no choroidal gland. Its optic nerve is represented by a small bundle of fibres which sweep over the edge of the retina to join the right normal optic nerve (fig. 1, PI. XXXIII,). The retina is small and elongated antero-posteriorly. The pigment-layer is present as such only in the posterior half of the retina. Anteriorly, the * For explanation of the Plate, see p. 452. |