44 THE EMBRYOLOGY OF THE EYE. 



forward as the subconjunctival tissue, a loose 

 meshwork of cells with many blood-vessels. 



7. CJioi^oid. — The fibres of the rudimentary 

 sclera, as we have seen, lie at first just exter- 

 nal to the capillary-vessel layer, which latter 

 rests upon the vesicle-wall (Fig. 10). Internal 

 to this fibrous layer the choroid is formed 

 about the capillary vessels. 



At this time we find the outer layer of the 

 vesicle-wall consisting of a single stratum of 

 hexagonal cells, darkly pigmented with rod^ 

 shaped particles of pigment. This stratum is 

 the pigment-epithelium. The inner margin of 

 this stratum is irreo^ular ; its outer maro^in is 

 smooth, and resting on this outer margin may 

 be seen the beginning of a delicate membrane, 

 which keeps growing thicker throughout the 

 entire course of foetal life. In the grown ani- 

 mal this is a fairly thick homogeneous mem- 

 brane, the so-called lamina vitrea of the 

 choroid. This membrane would seem to be 

 secreted by the pigment-epithelium. 



Directly on this thin homogeneous membrane 



