10 



J. PARSONS SCHAEFFER 



Figs. 6, 7, 8 and 9 Photomicrographs of frontal sections showing several 

 stages in the development of the nasolacrimal passages; a, b, c = remains of the 

 naso-optic furrow ;/= nasal fossa; e = eye; d== different stages of the anlage of the 

 nasolacrimal passages. 



Fig. 6 Note that there is no evidence of the anlage of the nasolacrimal pas- 

 sages in the region of the naso-optic furrow (a). Human embryo aged thirty- 

 three days. X 68. 



Fig. 7 Note the plug-like anlage of the nasolacrimal passages (d) from the 

 deep layers of the epidermis along the floor of the naso-optic furrow (6). Human 

 embryo aged from thirty-four to thirty-five days. X 68. 



Fig. 8 In this section the anlage of the nasolacrimal passages is considerably 

 advanced over that shown in fig. 7. Note, however, notwithstanding that it has 

 pushed its way into the underlying mesenchymal tissue, that the anlage still 

 retains its connection with the deeper layers of the epidermis along the floor of 

 the naso-optic furrow (<■). Human embryo aged about thirty-six days. X68. 



Fig. 9 In this section the anlage of the nasolacrimal passages has lost its con- 

 nection with the surface. Human embrvo aged forty-three days. X 68. 



