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BLIND VERTEBRATES AND THEIR EYES. 



not be determined with certainty. The relative development of the lens is not 

 dependent on age. The lens described by Wyman was undoubtedly one of the 

 scleral cartilages, for these cartilages are frequently nodular in this species and 

 one usually lies in front of the eye. 



The supposition of Wyman that one of the scleral cartilages is the lens need not 

 be criticised too severely. The structures descril^ed above as the lens are con- 

 sidered such, more because they could not be identified as anything else, and be- 

 cause nothing else that could with certaintv be considered a lens could be found 



Fig. s5. M Two Successive Sections through Right Eye of very Old Individu.-il 130 mm. long, showing a Lenslike Body. 

 (J) Outline Section of Left Eye of Individual 108 mm. long, showing highly developed Lenslike Body. 



aside from these structures, rather than on any direct evidence. The development 

 of the eye would indeed lead one to suppose that the lens is actually placed entirely 

 outside the optic cup, and in that case none of the structures here described can be 

 the lens. With as much varication as is found in all the structures it is not improb- 

 able that the lens may, in some indi\nduals, be found within the optic cup, and in 

 others outside of it. 



The progressive ontogenetic degeneration of the eye after maturity will be given 

 in the section dealing with its ontogenetic history. 



