100 ANIMAL LIFE 
around the forehead, its socket moving with 1t, until both 
eyes and sockets are transferred by twisting of the skull to 
Fia. 51.—The wide-eyed flounder (Platophrys lunatus). Adult, showing both eyes on 
upper side of head. 
the upper side. In some related forms or soles the small 
eye passes through the head and not around it, appearing 
finally in the same socket with the other eye. 
Thus in almost all the great groups of animals we find 
certain kinds which show metamorphosis in their post- 
embryonic development. But metamorphosis is simply 
development; its striking and extraordinary features are 
usually due to the fact that the orderly, gradual course of 
the development is revealed to us only occasionally, with 
the result of giving the impression that the development is 
proceeding by leaps and bounds from one strange stage to 
Fie. 52.—Development of a flounder (after Emery). The eyes in the young flounder 
are arranged normally, one on each side of head. 
another. If metamorphosis is carefully studied it loses its 
aspect of marvel, although never its great interest. 
