PLATE 8 



EXPLANATION OF FIGURES 



Microphotographs of horizontal sections of head, showing different stages in 

 the developing eye of the sparrow. Ap, annular pad of lens; Br, brain cavity; 

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

 appearing as a line or separation between the cells which have developed from 

 the posterior and anterior surfaces of the lens vesicle; Ld, lid; M, developing eye 

 muscles; N, nictitating membrane; OpSt, optic stalk; P, developing pigment 

 layer, the posterior wall of the original optic vesicle; R, the anterior, or invag- 

 inated wall of the optic vesicle which is developing into the remaining layers of 

 the retina; *S', developing sclerotic and chorioid layers. 



50 Left eye of embryo sparrow at the age of 3 days. X 40. 



51 Right eye of embryo sparrow at the age of 3 days. X 40. 



52 Right eye of embryo sparrow at the age of 4 days. X 40. 



53 Right eye of embryo sparrow at the age of 5 days. X 40. 



54 Left eye of embryo sparrow at the age of 5 days. X 40. 



55 Left eye of embryo sparrow at the age of 6 days. X 40. 



56 Right eye of embryo sparrow at the age of 7 days. X 40. 



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