PLATE 15 



EXPLANATION OF FIGURES 



Microphotographs of eyes of the young sparrow after hatching, showing 

 various stages in the development of the different parts. Ap. annular pad of 

 lens; B, bone of orbit; C. cornea; Cp, ciliary processes; CScl, cartilage of sclerotic 

 coat; F, developing fovea; Hg, Harder's gland; L, lenticular chamber; LI, lower 

 lid; Lu, upper lid; .V, nictitating membrane; OpN, optic nerve; Or, ora serrata; 

 P, pecten. 



86 Vertical section of the right eye of a young sparrow hatched 4 days pass- 

 ing through the center of the developing fovea and through the more distal por- 

 tion of the nerve entrance. A few more blood-vessels are found in the pecten. 

 X 10. 



87 Same series as figure 86 through the distal end of the pecten and nerve 

 entrance. A break in the cartilage layer of the sclera (appears as a light line, 

 CScl) shows where the distal part of the nerve pierces the eye wall. X 10. 



88 Same series as figure 86 passing through the extreme distal end of the 

 pecten beyond the last trace of the nerve entrance. The pecten and nerve 

 entrance thus extend from a little below the center of the eye obliquely down- 

 ward and forward almost to the ora serrata. X 10. 



89 Horizontal section of the left eye of a young sparrow 4 days old. This 

 shows the nictitating membrane well developed. This section passes through 

 the eye above the lens through the ciliary processes. X 10. 



90 Same series as figure 89 at a little lower level passing through the edge of 

 the lens and through the thickened margin of the loAver lid. X 10. 



91 Same series as figure 89 passing through the center of the lens and the 

 center of the developing fovea. The retina at the fovea is seen to be slightly 

 thinned. The laj^ers of the retina are well defined except the rods and cones. 

 These appear as conical projections with slender points having a total length of 

 about one-fifth that of the adult. The ciliary muscles appear well striated at this 

 age. X 10. 



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