DEVELOPMENT OF THE EYE. 



355 



rudimentary and without visual function. The iris is covered by the mesen- 

 chymal epithelium of the chambers. At the attached border of the iris the 

 vascular coat contains important muscle fibers and is there thickened to 

 form the ciliary body. This is also covered by a rudimentary pigmented 

 layer on its inner surface, the pars ciliaris retinae. At the ora serrata (Fig. 

 425) an abrupt thickening of the visual layer of the retina marks the boun- 



D 



FIG. 409. SECTIONS OP RABBIT EMBRYOS TO SHOW THE DEVELOPMENT OF THE EYE. A, 9^ days, 

 3.omm.;B, io days, 5.4 mm.;C, n days, 5.0 mm.; D, 14 days, 18 hours, 12.0 (8) mm.; E, 20 days, 

 29 mm. 



a. c. r., Arteria centralis retinae; c., cornea; c. a., anterior chamber, conj., conjunctiva; c. p., posterior 

 chamber; c. v., corpus vitreum; e. 1., eyelid; f. b., fore-brain; 1., lens; 1. e., lens epithelium; 1. f., lens 

 fibers; p. c., optic cup; o. n., optic nerve; o. v., optic vesicle; r. p., pigmented layer of the retina; 

 r. v., visual layer of the retina. 



dary between its ciliary and optic portions. The pars optica retinae extends 

 from the ora to the optic nerve, covered successively by the chorioid and 

 sclera. 



The cornea is the tissue in front of the anterior chamber, consisting of 

 a non-vascular mesenchymal tissue bounded posteriorly by mesenchymal 



