THE EMBRYOLOGY OF THE EYE. 5 1 



Any of the foetal vessels which are usually 

 absorbed may, however, remain permanently 

 in a degenerated form, so that we find as con- 

 genital anomalies, persistent pupillary mem- 

 brane, in the form of plaques on the capsule 

 of the lens or fibres arising from the region of 

 the minor vascular circle of the iris ; persistent 

 posterior vascular sheath of the lens, in the 

 form of plaques near the pole or strlatlons 

 running merldlonally on the capsule ; persist- 

 ent hyaloid artery, either its lenticular or 

 papillary insertion being preserved ; persistent 

 vitreous vessels of the 2d system ; and last, 

 connective-tissue masses of varying size In the 

 physiological cup of the papilla (Fig. 12), or 

 running from this point out into the vitreous 

 or extending along the limitans interna, all of 

 which anomalies are seen in the human eye. 



In the upper portion of Fig. 4 we see how 

 the vessels of the posterior lens-sheath run 

 over the anterior marorln of the vesicle-wall to 

 reach the mesoblastic tissue outside. This 

 communication remains throughout foetal life, 



