PLATE 4 



EXPLANATION OF FIGURES 



Very much enlarged camera-lucida drawings, showing the external parts of 

 the eye. c, trace of the chorioid fissure; e, ear; I. margin of lids; n, nictitating 

 membrane. X 15. 



24 Embryo at the age of 7f days. 



25 Embryo at the age of 8 days. 



26 Embryo at the age of 9 days. 



27 Embryo at the age of 10 days. 



330 



