. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. H2 COMPARATIVE ANATOMY. mid-brain, and thus may be easily overlooked (Figs'. 11-i and 115, Zll The prob .Cation t' tin- ecivUdlum into tin- ventricle of tlie mid-brain, seen only exceptionally in , is jnesmi a rule in ;UMns, IMI! the extent of its development varies much. Tin- pineal gland does not dili'er essentially from iliai of Elasmobrancha ami (Jamads, tliou-h it never extends tin- roof of tin- skull, ami remains within tin- brain- membranes. A,-
. Elements of the comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. H2 COMPARATIVE ANATOMY. mid-brain, and thus may be easily overlooked (Figs'. 11-i and 115, Zll The prob .Cation t' tin- ecivUdlum into tin- ventricle of tlie mid-brain, seen only exceptionally in , is jnesmi a rule in ;UMns, IMI! the extent of its development varies much. Tin- pineal gland does not dili'er essentially from iliai of Elasmobrancha ami (Jamads, tliou-h it never extends tin- roof of tin- skull, ami remains within tin- brain- membranes. A,- in Elasmobranchs, inferiores and a saccus vasculosus are pre>ent in connection \\itli tin- infumlibnlmu. Tin- saccus vasculosus is both L'lamlular ami vascular in structure, and its duct passes into the infundibulum ; hence ii is sometimes called tin- " infundibular ^; Ganoidei, Dipnoi, and Amphibia.—Even apart from the brains of Lepidosteus and Amia, which are formed on the Teleostean type, a common ground-plan cannot be laid down for the brains of other Ganoids, Dipnoaus, and Urodcles; in a certain tnea- suiv they may be said to form one group, but in many points they resemble thr"l»rain of Petromyzon. They are all distinguished by. Jl JWeCs Jfif Jf FIG. 116.—BIIAIN OF Polypteras biehir. Si>K' vii-\\. /, olfactory nerve ; II, optic nerve ; Lol, olfactory lobe ; VII, prosencephalon, with a lateral cleft at N, and the cerebral peduncles (Pcdc) at its base, wliich I'.uliate into the hemispheres at ''.•>•; Zll, thalamencephalon, at the base of which is the iufuiidibulnni (In/) with the pituitary body (//) ; ME, mid-brain : IIH, cere- bellum ; NH, medulla oblongata ; I!, spinal cord. a marked development uf the ci.'i-eb]-um, while the cei'ebellum is only represented hy~i~sinall "Transversi• 1'nld uf nervous matter on the anterior end of tin- medulla oblongata (Figs. 11G and 1 I 7, HH}. Tin- mid-brain is always paired; it encloses
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