•JO Journal of Comparative Neurology. 



/v^. 2. A portion of one of the epithelium cells and an adjacent 

 cell of the ental ganglion layer more highly magnified. 



F2g: 3. A portion of the ectal ganglion layer. 



F/^. 4. The termination of the fibres of the ectal ganglion layer in 

 the reticulum of the ectal zone. 



Ft^. ^. Portion of the superficial part of the tectum in Lepidosteus, 

 highly magnified to show the termination of the epithelium frame work. 



Figs. 6, 8, 9. Horizontal sections in the region of the habena from 

 Blicca Bjkorkna. Fig. 9 especially illustrates the origin of the "gelatinous 

 tracts" in the torus and their passage to various parts of the tectum. 



Fig. 7. Transverse section through the habena of Lncioperca. The 

 commissura transversa occupies the ventral part of the section. 



PLATE VIII. 



Figs. I, 2. Longitudinal sections of the brain of young specimens of 

 Belone. 



Fig. 3. Longitudinal section of the brain of fry of Trui.ta fario, with 

 a portion of the skin and nasal sac. S. b. sensory bails of skin; N. s., 

 nasal sac; Z.f., lateral ventricle; D s., dorsal sac; F/>., epipliysis ; f/., 

 habena; 77., torus longus ; To., tectum opticum ; On., optic nerve; /*. 

 tr., pyramidal tracts ; F. tr. 7\, ventral pyramidal tract; ffvpn , ]iypf)arium ; 

 K. r., velum caudale ; Mi., Meynert's bundle. 



Fig. 4. Transverse section through epiphysis, showing us connection 

 with the third ventricle. 



Fig. 5. Cells from a. Fig. 4 especially showing intimate connecli >n 

 with capillaries. 



Fig. i;a. Similar cells near ventricle. 



Fig. 6. Cells from d. Fig. 4. 



Fig. 7. Cells from the habena from section preceeding Fig. 4. 



Fig. 8. Horizontal section, brain of Haploidonotus to show the 

 Sylvian commissure [Com. syl.) and gelatinous fibres of torus [gel. J.) 



PLATE IX. 



Histological details of the midbrain. 



Fig. I. Portion of a transverse section of the tectum opticum of nine 

 days old Trutta fario. 



