Sargent. — Optic Reliex Apparatus. 



PLATE 9. 



Fig. 62. Paralichthys dcntatus, adult. Transverse section of the mesencephalon 

 and torus longitudinalis tlirouj^h the posterior commissure. X 15. 



Fig. G3. Cynoscion regalis, adult, section as above. X 15 



Fig. 64. Amhlyopsis spelaeus, adult. Transverse section of the root of the mesen- 

 cephalon and torus longitudinalis, caudad of tlie posterior commissure. 

 X 40. 



Fig. 65. Ameiurus nebulosus, adult, section as above. X 40. 



Fig. 66. Pseudopleuronectes americana, adult. Sagittal section tlirough the canalis 

 centralis, in the middle portion of tlie cord, showing the branching of 

 Ueissner's fibre. Anterior is nppermost and ventral at the left. X 1001). 



Fig. 67. Squalus acanthias, embryo, 10 mm. long. Sagittal section through tlie 

 posterior portion of the canalis centralis, showing two of the posterior 

 canal-cells, and some of the fine branches entering the ventral wall of 

 the canal. X 1350. 



