There should be noticed (1) the increase in the flexure of the brain accompanying a rectification of the cranial axis; (2) the elongated pineal gland, and (3) the structure of the optic thalamus.
Figs. 6a, 6b, 6c. Views from the side, from above, and from below, of a brain of Scyllium stellare during a slightly later stage than Q.
Figs. 7a and 7b. Two longitudinal sections through the brain of a Scyllium embryo during stage Q. Zeiss a, ocul. 2.
7a cuts the hind part of the brain nearly through the middle line; while 7b cuts the cerebral hemispheres and pineal gland through the middle.
In 7a the infundibulum (1), cerebellum (2), the passage of the restiform tracts (rt) into the cerebellum (3), and the rudiments of the tela vasculosa (4) are shewn. In 7b the septum between the two lobes of the cerebral hemispheres (1), the pineal gland (2), and the relations of the optic thalami (3) are shewn.
Figs. 8a, 8b, 8c, 8d. Four transverse sections of the brain of an embryo slightly older than Q. Zeiss a, ocul. 1.
8a passes through the cerebral hemispheres at their junction with the olfactory lobes. On the right side is seen the olfactory nerve coming off from the olfactory lobe. At the dorsal side of the hemispheres is seen the pineal gland (pn).
8b passes through the mid-brain now slightly bilobed, and the opening into the infundibulum (in). At the base of the section are seen the optic nerves and their chiasma.
8c passes through the opening from the ventricle of the mid-brain into that of the cerebellum. Below the optic lobes is seen the infundibulum with the rudiments of the sacci vasculosi.
8d passes through the front end of the medulla, and shews the roots of the seventh pair of nerves, and the overlapping of the medulla by the cerebellum.