46 THE EMBRYOLOGY OF THE EYE. 



With the appearance of the pigmented cells 

 the vessels become more numerous and the 

 pigmented and unpigmented cells form a 

 delicate meshwork about them. The external 

 cells form long fibres, which are readily de- 

 tached from the rudimentary sclera, and 

 among these fibres free endothelial cells are 

 found. 



8. Iins, ciliajy body, and pupillary membrane. 



a. The iris and ciliary body are composed 

 of an epiblastic and a mesoblastic portion, 

 each of which may be considered separately. 



Epiblastic portion. In Fig. 3 we see the 

 folded anterior margin of the secondary optic 

 vesicle, to the left the two layers some dis- 

 tance apart, to the right the two layers in ap- 

 position. In Fig. 7 the outer layer has taken 

 on its pigment, and the Inner layer has become 

 thinned near the margin. The folded margins 

 turn it toward the lens, and in Fig. 8 they are 

 in contact with it. At this stage we may 

 notice a slight curving of the vesicle-wall near 

 its folded margin, which becomes later a dis- 



