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Show 22 DR. J. r. GLMMILL ox [May 12, PLATE II. Fig. 9. Ventral ends of the Meckelian, hyoid, and branchial cartilages of the monstrosity illustrated in figs. 3 and 4 (see pp. 7, 8). Fig. 10. Ventral ends of the Meckelian, hyoid, and branchial cartilages ot the monstrosity illustrated in figs. 5 and 6 (pp. 11, 12). Meek. Outer Meckelian bars. Meek.' Inner or adjacent Meckelian bars united and greatly reduced. GH. Glossohyal. BE. Hypohyal. LH. Ceratohyal. BH'. Inner or adjacent hypohyals partly united. LH'. „ „ ceratohyals united. Ill, IV, V, VI, VII. The branchial cartilages. Cop. Copular pieces, the anterior one being bifid. Fig. 11. Transverse section of a composite pectoral fin, from a monstrosity in which union took place just behind the pectoral fins (see p. 19). Scap., Cor. Scapular and coracoid parts respectively of the coraco-scapular bars. The ventral ends of the coracoid parts are united. CL. The limb-cartilages united for the greater part of their length. R. The rays (not cartilaginous). Fig. 12. Diagram of the aorta and its roots in the monstrosity referred to on p. 9. Ao'. Aorta, the two limbs uniting further back. I, II, III, IV. Aortic roots, i. e. branchial veins. Car. Carotids. Aa. Artery to pseudobranch, a branch of the 1st branchial. Psbr. Pseudobranch. A.Chor. Choroidal artery. A.Chor.' The arteries for the choroidal glands of the inner or adjacent pair of eyes. They arise by a single stem from the middle of a vessel connecting the aortic roots on either side, and go to the choroidal glands without passing through a pseudobranch. Fig. 13. Diagram of ventral aorta, aorta and aortic roots in the monstrosity illustrated in figs. 5, 6, 16 (see p. 13). Lettering as above, with in addition : 214. Ventral aorta and its branches 1, 2, 3, 4. Car.' Inner or adjacent carotids, giving off Aa' arteries to the inner or adjacent pseudobranchs Psbr.' It will be seen there are two sets of carotid and afferent pseudobranch arteries, the inner sets being derived directly from the ventral aorta. The ventral aorta arches dorsally in the septum between the two mouths of the monstrosity, reaches the base of the skull, and then divides into two limbs which are continued backwards to join the aortic-collecting roots on either side. Fig. 14. Outline of central cavity of brain of normal Trout embryo. Lettering as in fig. 16. Fig. 15. Outline of central cavity of brain of the monstrosit}' illustrated in figs. 3, 4, & 9 (p. 8). Lettering as in fig. 16. Fig. 16. Outline of central cavity of brain of the monstrosity illustrated in figs. 5, 6, 10 (p. 12). C.F.B. Cavity of the hemispheres. C 3rd V. „ 3rd ventricle. COL. „ optic lobes. CIt. „ iter a tertio ad quartum ventriculum. Cith V. „ 4th ventricle. Spc. „ spinal cord. Fig. 17. Outline of transverse section of central cavity in anterior part of optic lobe region of the brain illustrated in fig. 15. There are two infundibula and two sets of hypoarial cavities, while the main optic lobe cavity is single (p. 8). COL. Cavity of optic lobes. Inf. Infundibulum. Hyp. Hypophysis sac. Hya. One of the hypoarial cavities. |