

469 



tuin, the epidermk l.y means of a solid epithelial cord (1st). Upon 

 otod <>n the 1. -mi-vesicle naturally pushes the adjacent 

 ral wall vesicle before it and folds the 



against the median wall. 



At time with the development of the lens, the primary 



nptic ve.-icle is also in\ aviated from below along a line which 

 ir.iin tin- epidermis to the attachment .f the >t., 

 tde, and is even ton tinned along the I some distance 



265 aits). A loop of a blood-vessel from the enveloping 

 connect i\e i:>sue, embedded in soft, irel-mumis substance (gl), 

 grows against the lower surface of the primary optic vesicle an 

 -talk, and pushes up before it the 



lower wall. 



In con-equence of the two inva 



the optic vesicle acquires the 



form of a beaker or cup, the foot of 



which is represented by its stalk (Sn). 



But the optic cup, as we can from this 



time forward designate the structure? 



e.\hil>it> tuo peculiarities Kir 



s it were, a defect (fig. 2(j^ 



iu it- low. r wall ; for there runs along 



the latter from the margin of the 



1 opening which embraces the 



lens (/) to the attachment of the stalk 



(Sn) a fissure (aus), which is caused by 



the development of the vitreous body 



(gl) and bears the name foetal optic 



<>roid fasure]. At first 



it is rather wide, but then becomes narrower and narrower by the 

 approximation of its edges and finally closed alt..-, i her. Secondly, 

 the optic cup, like the toy called the cup of Tantalus, is prov 

 with double walls, which are continuous with each other alom: 

 edge of the front opening and also along the fissure. They will 

 henceforth be designated as inner (figs. 264 B and 265 ib) and outer 

 (ab) layers; the former is the invaginated, the latter the unin- 

 vaginated part of the primary optic ves; 



At the bejrinniiiir of the infoldim: the two layers are separated by 

 a broad space (h), which leads into the third v. utricle through the 

 stalk of the vesicle (Sn) ; but afterwards the >pace Incomes reduced 

 proportionally to the increase in the size of the vitreous body. 



Fig. 265 Plastic representation of 

 the optic cup with lens and 

 vitreous body. 



aft, O;:- 



wall ; A, cavity between 

 the two walls, which later dis- 

 appear* entirely ; Sn, fundament 

 of the optic nerve. (Stalk of the 

 vesicle with a farrow on 

 iU lower surface.) am, Optic 

 [choroid] fissure ; gl, Titreoos 



I* Hi 



