OUR FACE FROM FISH TO MAN 



by convergent evolution in adaptation to similar 

 functional needs. 



The paired eyes of the modern Limulus and the 

 scorpions represent specialized offshoots of the 

 annelid and primitive crustacean types (Plate, 

 1924, pp. 537-561). Patten and others have 

 attempted to show how they might have been 

 tranformed into the vertebrate eyes, but most 

 authorities consider that there is no direct evidence 

 in favor of this view and the profound differences 

 between the eyes of arthropods and those of 

 vertebrates have always been considered a grave 

 objection to Patten's theory of the origin of the 

 vertebrates from arthropods related to the euryp- 

 terids and to Limulus. 



ORIGIN OF THE PAIRED EYES OF VERTEBRATES 



We have seen above that a comparative study 

 of the eyes of invertebrates shows several steps 

 in the evolution of such elaborately constructed 

 paired eyes as those of the cephalopods and there- 

 fore gives us a general idea how the somewhat 

 similar paired eyes of vertebrates may have been 

 produced. More direct evidence as to the origin 



of the vertebrate eye is wanting. The lancelet 



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