86 



THE DARWINIAN THEORY 



fish to escape the notice of its enemies ; and the left 

 eye, no longer of use in its original position, is 



Fig. 



6 



'teix^--^ 



.A \.Jk\ 



stf&SSSR 



; 



^iim 



:r>7 



Voting and adult specimens of the Flounder (Pleuronectes flesus), to illus- 

 trate the shifting of the eye from one side of the head to the other 

 during the growth of the fish, 



A. — A young Flounder six days after hatching. The head is symmetri- 

 cal, and the eyes one on each side. >: 4 



B. — A young Flounder, probably about a month old. The fish is 

 gradually acquiring the characteristic shape of the adult, and the head is 

 becoming twisted, the eye of the right side being displaced slightly down- 

 wards, and the eye of the left side coming into view over the top of the 

 skull. x 4 



C. — An adult Flounder showing the characteristic shape of the flat-fish, 

 and the complete migration of the left eye over to the right side of the 

 head. x \ 



gradually displaced upwards on to the top of the 

 head, and then shifts over to the right side ; the 



