PLATE 2 



EXPLANATION OF FIGURES 



Very much enlarged camera-lucida drawings, showing the development of the 

 external parts of the English sparrow eye. b, beginning of beak; c, chorioid fis- 

 sure; e, ear pit; I, margin of lids; ?«, outline of eye as seen through the ectoderm; 

 n, beginning of the nictitating membrane. X 15. 



16 Head of embryo 2 days old. 



17 Head of embryo 2| days old. 



18 Head of embryo 3 days old. 



19 Head of embryo 4 days old. 



20 Head of embryo 5 days old. 



21 Head of embrvo 6 days old. 



326 



