4 PROCEEDINGS OP THE AMERICAN ACADEMY 



The young Flounder has already attained a considerable size, before 

 any signs appear of the change in the position of the eye on the left 

 side (see PI. III. figs. 3-5 and PL IV. fig. 1), and before the young fish 

 shows the least tendency to favor one side over the other. Not until 

 the young fish is fully three-eighths of an inch in length can the first 

 slight difference be perceived in the position of the two eyes (when 

 seen from above), the left eye being somewhat in advance of the 

 other. In this species, the Flounder eventually lies down on the left 

 side, which becomes colorless. In order to prevent repetitions, we shall 

 call this the case of a right Flounder (dextral), — that is, of a Flounder 

 colorless on the left side, and where the left eye has passed over to the 

 right side, — calling the sides, at the same time, either blind or white, 

 and the opposite ocular or colored. 



Plates III. and IV. show very well the changes of form through 

 which the young dextral Flounder passes before it finally assumes 

 the appearance of the adult, and habitually rests with its colorless side 

 upon the ground. All young Flounders, even long after they have all 

 the characteristics of the adult, very frequently swim vertically for quite 

 a length of time, or else swim near the surface, with the undulating 

 movement they have when swimming over the bottom, their heads well 

 raised, and bodies carried flat, parallel to the surface. Even quite old 

 Flounders sometimes are caught swimming near the top of the water. 

 Almost all the stages figured in Plates III. and IV. were caught near 

 the surface, swimming vertically, like any other young bony fishes ; but 

 this they do only when they come up to feed, while the water is very 

 smooth, about ten in the morning, on very bright sunny days, when they 

 may be seen eagerly devouring swarms of embryo Crustaceans, of all 

 orders. The young of other fishes seem to share this habit; for of the 

 latter I have examined no less than twenty-five species, caught at va- 

 rious times with a hand-net, swimming near the surface of the water, 

 on bright sunny days, when not a ripple ruffled the sea. With the 

 least movement, all the more delicate of these embryos vanish ; leav- 

 ing only the older and more vigorous, which in their turn disappear, 

 and seek shelter in deeper water. Only when the young fishes are 

 old enough to be recognized as the young of their tribes, do they ven- 

 ture to join them in their ordinary haunts. 



PL V. figs. 7-11, PL VI., and PL VII., on the other hand, give us in 

 general the changes of form a young sinistral Flounder undergoes 

 from the time it leaves the egg until it assumes the characteristics 

 of the adult. The explanation of the plate will give all the necessary 

 details of the changes, which are mere repetitions of those described 



