34 



BLIND VERTEBRATES AND THEIR EYES. 



Very markecTchanges have been brought about in the specimen 70 mm. long. 

 The pupil is now an oblique channel and the lower margin of the iris overlaps 

 the upper margin. On the left it is more nearly as in the younger stages, but 

 wider (48 /a). The free margin of the iris now reaches the enormous thickness of 



Fig. 7. (a) Right Eye of Specimen 70 mm. long. (6) Right Eye of Specimen 90 mm. long. 



56 fi to 80 fj,. The pigmented epithelium has rolled in more, so that the elongated 

 nuclei, free from pigment, are crowded together in the region of the ora serrata. 

 The pupil is filled in part with pigment, evidently of choroidal origin (fig. 7 a). 



In the right eye of the specimen 90 mm. long the choroidal pigment has forced 

 its way into the interior of the eye and forms a conical-shaped mass like a plug in 



