Fig. 19 represents the brain of an average bony fish. It consists of six swellings in a line, one before the other. Beginning from the end towards the spinal cord, they are designated as follows, viz.: a single median lobe, the medulla (Metencephalon), m; then in front of this is another single median lobe, the cerebellum (Epencephalon), cb; then the optic lobes (Mesencephalon), right and left, ol; then the thalami (Thalamencephalon), which are small and hidden from view by the encroachment of the two adjacent segments; then the cerebrum (Prosencephalon), cr; then, finally, the olfactory lobes (Rhinencephalon), of. In this fish the largest of the segments are the optic lobes, ol. [Illustration: FIG. 20.—Brain of Reptile (Turtle). A, dorsal view; B, side view; of, olfactory lobe; cr, cerebrum; th, thalami; ol, optic lobes; cb, cerebellum; m, medulla.] The reptile’s brain (Fig. 20) shows similar parts with the same serial arrangement. The reptile is a higher creature, a more intelligent animal, than the fish; and in consonance with this fact the cerebrum, cr, is the larger and more dominant part of the brain instead of the optic lobes, ol. [Illustration: FIG. 21.—Brain of Marsupial (Opossum). A, side view; B, dorsal view; of, olfactory lobes; cr, cerebrum; ol, optic lobes; cb, cerebellum; m, medulla. Thalami concealed from view by the backwardly extended cerebrum; also the optic lobes are partially covered by the cerebrum.] [Illustration: FIG. 22.—Brain of Lemur (Lemur nigrifrons). A, dorsal view; B, side view; cr, cerebrum; cb, cerebellum; m, medulla.]