THE EMBRYOLOGY OF THE EYE. 43 



come to form a simple layer of capillaries rest- 

 ing on the vesicle-wall (Fig. 8). The meso- 

 blastic cells then become spindle-shaped and 

 run parallel to the vesicle-wall, and later the 

 spindle-cells form fibres. In Fig. lo we see 

 outside the vesicle-wall this thin fibrous layer, 

 which is the rudimentary sclera. External to 

 it and at this period not sharply differentiated 

 from it is the general mass of indifferent meso- 

 blastic cells filling the orbital cavity. A little 

 later branched pigmented cells appear at the 

 outer margin of the rudimentary sclera, sep- 

 arating it from the orbital tissue. These pig- 

 mented cells are rarely found in the human 

 sclera. 



External to the pigmented cells is a thin 

 layer of loosely meshed cells, and external to 

 these, particularly in the anterior segment, we 

 find a very thin fibrous layer similar to the 

 sclera, which represents the capsule of Tenon. 

 Anteriorly the fibres of the sclera are continu- 

 ous with those of the cornea (Fig. 9). The 

 loose tissue external to the sclera continues 



