174 



Instincts, Habits, and Adaptations 



it. In most flounders the eye seems to move over the surface 

 of the head, before the dorsal fin, or across the axil of its first 

 ray. In the tropical genus Platophrys the movement of the eye 

 is most easily followed, as the species reach a larger size than 

 do most flounders before the change takes place. The larva, 

 while symmetrical, is in all cases transparent. 



In a recent study of the migration of the eye in the winter 





FIG. 126. 



FIG. 127. 



FIGS. 126, 127. Larval stages of Platophrys podas, a flounder of the Mediterranean, 

 showing the migration of the eye. (After Emery.) 



flounder (Pseudopleuronectes americanus) Mr. Stephen R. Wil- 

 liams reaches the following conclusions: 



1. The young of Limanda ferruginea (the rusty dab) are 

 probably in the larval stage at the same time as those of Pseu- 

 dopleuronectes americanus (the winter flounder). 



2. The recently hatched fish are symmetrical, except for the 

 relative positions of the two optic nerves. 



3. The first observed occurrence in preparation for meta- 

 morphosis in P. americanus is the rapid resorption of the part 

 of the supraorbital cartilage bar which lies in the path of the 

 eye. 



4. Correlated with this is an increase in distance between 



