8 PROCEEDINGS OF THE AMERICAN ACADEMY 



angle of at least one hundred and eighty degrees. Thus, our trans- 

 parent Flounder, which I did not at first recognize as the Plagusia of 

 Steenstrup, could readily, by looking obliquely, see with great distinct- 

 ness, through the transparent tissues, what was passing on the opposite 

 side of the body. 



I made all preparations to watch the changes in this interesting 

 fish, should any such take place ; and, a couple of days afterwards, I 

 noticed the first change in the position of the eye (PI. X. fig. 3) of 

 the right side. No less than fifteen of these transparent Flounders 

 were caught at the surface, with the hand-net, at the mouth of the 

 harbor of Newport, close to the shore, on a very quiet and brilliant 

 morning. They were then swimming vertically, and rushing violently 

 after the minute Entomostraca swarming on the surface ; but, as 

 soon as they were confined in shallow glass jars, they turned on the 

 right side, where they would often remain immovable on the bottom 

 for hours. They were rapid in their movements when disturbed ; 

 frequently jumping out of the water and over the sides of the 

 dishes, to a considerable distance. Though they appear so delicate, 

 they do not seem to suffer, any more than other Flounders, from their 

 momentary stay on dry land. When swimming vertically, they usually 

 move obliquely, the tail kept much lower than the head ; and, when 

 seen endways, are more or less curved, owing to the extreme tenuity 

 of their body (PI. X. fig. 2). 



During the change of the eye from the blind to the binocular side 

 of the body, the outline of the young fish becomes more rounded 

 anteriorly ; and the minute, dotlike yellow and black pigment spots, 

 hardly perceptible in Fig. 1, PI. X., form somewhat more prominent 

 patches on the sides of the body, and radiating lines parallel to the 

 fin-rays on the dorsal and anal fins (PI. X. fig. 11). 



The right eye (PI. X. fig. 3) could, when the fish was in profile, be 

 seen through the head slightly in advance, and somewhat above the left 

 eye ; the right eye in that position, owing to the great transparency of 

 the body, being quite as useful as if it had been placed on the left side. 

 In the following stages, the right eye rises gradually more and more 

 above the left eye, in a somewhat oblique direction towards the fifth or 

 sixth anterior ray of the dorsal, until the fifth or sixth day, when the 

 right eye can be seen entirely clear of the left eye, well above it (PL X. 

 fig. 4). Owing to the great size of the orbit, the left eye, when seen from 

 the left side (PI. X. fig. 3), sometimes appears shot a little behind the 

 right, especially after the mofaion of rotation has commenced ; for we 

 find that in this Flounder, as well as in the others, the transfer of the 



