472 



EMBRYOLOGY. 



wall, on the contrary, the cells increase greatly in length (fig. 266 If) 

 and grow out into long fibres, which form a protuberance projecting 

 into the cavity of the vesicle. The fibres stand perpendicular to the 

 posterior wall, are longest in its middle, become shorter towards the 

 equator of the lens (figs. 266, 267 l) 9 and finally appear as ordinary 



pi r 





k d h he 



Tig. 267. Part of a section through the fundament of the eye of an embryo Mouse. Somewhat 

 older stage than that shown in fig. 266. After KESSLER. 



A part of the lens, the rim of the optic cup, the cornea, and the anterior chamber of the eye. 

 pi, Pigmented epithelium of the eye ; r, retina ; rz, marginal zone of the optic cup ; ff, blood- 

 vessels of the vitreous body in the vascular capsule of the lens ; tv, tunica vasculosa lentis ; 

 x, connection of the latter with the choroid membrane of the eye ; i', transition of the lens- 

 epithelium into the lens-fibres ; le, lens-epithelium ; Tc, anterior chamber of the eye ; 

 d, DESCEMET'S membrane ; h, cornea ; lie, corneal epithelium. 



cylindrical cells; these in turn become still shorter and are 

 continuous with the cubical cells (le) of the lens-epithelium. In this 

 way there exists at the equator a zone of transition between the 

 fibrous portion and the epithelial part of the lens. 



The next change consists in the elongation of the fibres until their 

 anterior ends have reached the epithelium (fig. 267). Consequently 



