PLATE 9 



EXPLANATION OF FIGURES 



Microphotographs of horizontal sections through the head, showing different 

 stages in the developing ej^e of the sparrow. Ap, annular pad of lens; Br, brain; 

 C, cornea; E, ectoderm; L, lenticular portion of lens; Lc, lenticular chamber rep- 

 resented by a narrow line; Ld, lid; M, developing eye muscle; A', nictitating 

 membrane; ON, optic nerve; P, pecten; Pg, pigment layer of the retina; R, remain- 

 ing portion of retina: S, developing sclerotic and chorioid coats. 



57 Right eye of embryo of 7i days, through the center of the lens. X 40. 



58 Right eye of embryo of 71 days, showing the early development of the 

 nictitating membrane and lids. X 40. 



59 Left eye of embryo of 7? days, showing the center of the lens. The dif- 

 ferent parts of the developing lens are very noticeable and the retina has in- 

 creased in thickness. The anterior part of the eye is at the bottom of the figure. 

 X40. 



60 Embryo of 7j days. Section passes through the nerve entrance and shows 

 the first trace of the pecten. X 40. 



61 Embryo of 7f days. Section passes through the nerve entrance and 

 shows the pecten appearing as a conical projection, a little more advanced in 

 development than in figure 60. X 20. 



62 Same series as figure 61, the section passing through head at a different 

 level. X 20. 



340 



