366 Journal of Comparative Neurology. 



conspicuous retinal blood vessels (bv). The nerve fibers can be traced through 

 a mass of ganglion cells almost to the lens. X 29. 



Fig. 34. Horizontal section through the center of the lens of adult eye 

 hardened in zc'c potassium bichromate. The lens is here very much reduced in 

 size. X 39. 



Fig. 2^. Vertical section through the center of the lens of opposite eye 

 of the same adult as Fig. 34, eye hardened in same fluid. The lens is again 

 seen to be very much reduced in size and the shape is very irregular. A num- 

 ber of blood vessels {bv.) are represented in the mass of ganglion cells. X 29. 



Fig. 26. Section through the center of the lens of an adult eye hardened 

 in a^p potassium bichromate. This shows an extremely large lenticular shaped 

 lens. X 29. 



Fig. 2J. Section through the center of the lens of an adult eye hardened 

 rn \0(Jl^ formalin. 



Fig. 28. Section of the retina through the region A-B of Fig. 27 magni- 

 fied to show the cells of the retina. X i S^- 



Fig. 2g. Lens cells of adult magnified to show vacuoles (z'), nuclei («) 

 and nucleoli («/). X ^50. 



^^S- 30. Rods (r) and cones (c) and their nuclei {rn and en) of an adult. 

 The entire thickness of the outer nuclear layer is represented, the inner bound- 

 ary being represented by the line o-m. Hardened in 10^ formalin. X 700. 



P^S- 31- Ganglion cells of adult showing the dendritic (</) and ax- 

 onic {ax) processes. These two cells are from different parts of the retina. 



X 700. 



^iS- 32- Cells of the inner nuclear layer. X 700. 



Fig. jj. Cells of the outer nuclear layer. X 700. 



^'S'- 34- -^ portion of the optic nerve of the young at birth taken from 

 the region where the line "j" crosses the nerve in Fig. 7. Magnified to show 

 nerve fibers (»/) and the cells of the optic stalk. X 250. 



^^S- 35- A portion of the optic nerve of the young at birth from the 

 region indicated by C-D oi Fig. 34 more highly magnified. The nerve fibers 

 («/) and the cells of the optic stalk (c. op.) are seen more or less interming- 

 ling. X 700. 



Fig. j6. Ganglion cells of the young at birth showing the axonic pro- 

 cess [ax) and the absence of dendrites. 



■^*i'- 37- A group of ganglion cells from the retina at birth in which 

 some are seen which have not yet produced axones. 



P*S- 3^- A. typical ganglion cell from the retina of the young at birth. 

 Such a cell is only occasionally found at this stage. The most common types 

 are shown in Fig. 37. X 700. 



■^^i^- 39- Cells from the inner nuclear layer at birth. X 700. 



Fig. 40. Cells from the outer nuclear layer at birth. X 7oo. 



