PLATE 16 



EXPLANATION OF FIGURES 



Microphotographs of sections through the eye of the sparrow at different ages 

 showing advancing stages in the development of the various structures. Ap, 

 annular pad of lens; C, cornea; Ch, chorioid; Chs, chiasma; Cp, ciliary proc- 

 esses; Cm, ciliary muscles; Hg, Harder's gland; /, iris; L, lenticular portion of 

 lens; Lc, lenticular cavity; Ld. lids; Lg, lacrimal gland; M, eye muscles; N, nic- 

 titating membrane; OpN, optic nerve; Or, ora serrata; P, pecten. 



92 Horizontal section of the left eye of a young sparrow 4 days after hatching 

 through the center of the lens. X 10. 



93 Same series as figure 92 through the nerve entrance and folds of the pecten. 

 At this age the pecten has eighteen folds, this is only two less than in the adult. 

 The blood-vessels, however, are not well formed as in the adult. X 10. 



94 Vertical section of the eye of a young sparrow about 5 or 6 days after 

 hatching. 



95 Posterior portion of the eye of the same series as figure 91, passing through 

 the nerve entrance and the center of the developing fovea. The very noticeable 

 thickening of the chorioid is seen just back of the fovea. The fovea is pitting in 

 slightly and the retinal layers are beginning to thin out somewhat in the imme- 



■ diate center. The rods and cones have reached almost their adult length and the 

 pigment layer is sending processes between the outer segments of the rods and 

 cones. X 10. 



96 Horizontal section through the eye of a young sparrow of about 6 days 

 after hatching, passing through the center of the developing fovea, but to one 

 side of the center of the lens. The zonula fibers are seen. X 10. 



97 Same series as figure 96 passing through the edge of the pupil. X 10. 



98 Same series as figure 96 passing through the center of the lens. X 10. 



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