OUR FACE FROM FISH TO MAN 



morphology than it is to any known invertebrate. 

 In other words, while we can only surmise what the 

 history of the eye may have been below the verte- 

 brate stage, we have the most convincing evidence 

 that once that grade of organization of the eye had 

 ciliari/ . 



ofslfull 



Fig. 99. The Right Ete of a Shark in Horizontal Section 



(from Plate, after Franz). 



(From Allgem. Zool., Gustav Fischer.) 



been attained, it was transmitted by heredity with 



only minor improvements from fish to man. 



Although the human eye is undoubtedly derived 



remotely from one that was in general like the 



shark type (Fig. 99), from which it has inherited 



even the principal layers of the retina, it shows also 



many progressive changes beyond that of the shark 



in adaptation to vision in the air rather than in 



water. Its lens, being relatively smaller and 



192 



