DEVELOPMENT OF THE OPTIC NEEVE OF VERTEBL'ATES. 103 



20. MuLLER, W, — ' Ueber die Stamraes Entwickelung des Sehorgans der 



Wirbelthiere,' Leipzig, 1874. 



21. Okr. — "Contribution to the Embryology of the Lizard," 'Journal of 



Morphology,' vol. i, No. 2, 1887. 



22. Oer.— "Note on the Development of Amphibians," 'Quart. Journ. 



Micr. Sci.,' vol. xxix, 1887. 



23. ScHAFER. — "Embryology," Part 1 of vol. i of 'Quain's Elements of 



Anatomy,' 10th edition, 1890. 



24. Stieda. — " Studien iiber das ceutrale Nerveusystem der Vogel uud 



Saugethiere," ' Zeits. f. wiss. Zool.,' Bd. xxx, 1868. 



25. Spencer, W. B.— " On the Presence and Structure of the Pineal Eye in 



Lacertilia," 'Quart. Journ. Micr. Sci.,' 188G. 



EXPLANATION OF PLATES XI & XII, 



Illustrating Mr. Richard Assheton's paper '^ On the Develop- 

 ment of the Optic Nerve of Vertebrates and the Choroidal 

 Fissure of Embryonic Life.^' 



Alphabetical List of Reference Letters for all the Figures. 



BR. Brain. B. V. Blood-vessel. C. Cone. C. OP. V. Cavity of the 

 optic vesicle. CH. Choroid fissure. CH'. Choroid fissure, outer end. D. 

 Growing rim of optic cup. FR. Radial fibres. G. Cells of the ganglionic 

 layer of the retina. L. Lens. L. C. Cavity of lens. M. COM. Middle com- 

 missure. MES. Mesoblastic sheath round optic nerve and stalk. MO. Outer 

 molecular layer. N. Neuroblast. NI. Inner nuclear layer. OP. N. Optic 

 nerve. OP. RC. Optic recess. OP. S. Optic stalk. OP. S'. Cells of optic 

 stalk separated. P. Pigment layer of retina, i. e. posterior wall of optic 

 vesicle. R. Rods. R. CH. Edge of choroid fissure. RS. Rim of optic cup. 

 TR, CR. Trabecula cranii. X. Neuroblast of inner nuclear layer. 



Fig. 1. — Horizontal section of the right eye of a 10 mm. tadpole. 



Fig. 2. — From a horizontal section of a 10 mm. tadpole. In this the optic 

 stalk, OP. S., and optic nerve, OP. N., are cut across transversely to their 

 length. 



Fig. 3. — From a horizontal section of a 10 mm. tadpole. The optic nerve 

 and optic stalk are seen separating at their junction with the brain. 



Fig. 4. — From a sagittal section of a 7 mm. tadpole. The figure shows 



