lO NAKAGAWA. 



EXPLANATION OF PLATE. 



Fig. I. Cerebrum of Spelerpcs rtiher. Transverse section. X 40. 



Fig. 2. The same of Tropidonotus, X 18. 



Fig. 3. The same of Emys. X 20. 



Fig. 4. Of Colutnba livia. X 80. 



Fig. 5. 0{ Didelphys. X 120. 



Fig. 6. Part of the transverse section of the tectum opticum q{ Rana. X no. 



Fig. 7. The same of Tropidonotus. X 180. 



Fig. 8. Oi Eniys. X 150. 



Fig. 9. Of Columba livia. X 90. 



Fig. 10. Transverse section of the optic lobes oi Rana. X 18. 



Fig. II. Vertical section of the same. X 20. 



Fig. 1 2. Vertical section of the optic lobe of Tropidonotus. X 22. 



A, 1st white layer of the tectum opticum. B, ist gray layer. C, 2d white layer. 

 D, 2d gray layer. E, 3d white layer. F, 3d gray layer. G, 4th white layer. //, 4th 

 gray layer. BCD, layer corresponding to the layers B, C, and D, in Rana. CD, 

 layer corresponding to the layers C and D in Rana. 



lit, lit', lit", lit'", tracts of the optic nerve. ////, tract of the oculo-motor 

 nerve. IJ't, 17, Vlt, tracts of IV, V, and VI nerves respectively. Vn, nucleus of 

 the Trigeminus. /', fibres descending from B to D. cat, corpus callosum. eg, cortical 

 gray, eg', ist cortical gray layer, eg", 2d cortical gray layer, c. t. o. commissura 

 tecti optici. Di, diencephalon, or the optic thalamus. Ep, ependyma. fl super- 

 ficial white layer. /", 2d white layer. F. />. h. basal prosencephalic tract. For, 

 fornix, msc, mesocccle. I\It, metencephalon. pre, procoele. prcs, anterior com- 

 missure, vg, ventricular gray. 



