ADJUSTMENT OF FLATFISHES 443 



the white bottom). Photographs were now made, in which the 

 two fishes were taken together, first on the gray bottom (fig. 11^- 

 12c, plate 13), then on the white bottom. Both of these showed 

 very plainly the difference of shade between the two fishes. 



The specimens were then transposed, no. 11 being placed upon 

 the white bottom, no. 12 being placed upon the gray bottom. 

 After two days, no. 11 appeared to be paler than 12, and after 

 four days it w^as certainly so. They were compared, as before, 

 and again photographed together, first upon the gray bottom 

 (fig. llh-12d), then upon the white bottom. The relative shade of 

 the two fishes had obviously been reversed. 



The two animals were once more transposed, and with similar 

 results, though no photographs were taken. 



Is the behavior of the fish influenced by the degree of its adaptation to 



the background? 



As has already been pointed out, most specimens covered them- 

 selves more or less with the gravel or sand in which the}^ lay. In 

 some cases, the marginal fins only were concealed; but in a few 

 instances the entire body was buried, only the eyes protruding. 

 So far as my observations go, the fish was just as likely to cover 

 itself with the bottom material when its color and pattern were 

 highly adapted to this as it was when they were glaringly ill- 

 adapted. When specimen no. 10 was taken from a pale back- 

 ground and placed in black sand, it buried itself with extreme 

 rapidity, and remained completely concealed. In this instance 

 the fish was at the outset utterly out of harmony with the bottom. 

 It was noted, however, that this tendency to hasty concealment 

 beneath the sand was just as marked after the fish had assumed 

 a shade not far different from that of the latter. 



In contrast to the last example, specimen no. 11, though even 

 more conspicuously out of harmony with its background, did not, 

 at first, make any endeavor to bury itself when placed on the 

 magnetite sand. 



In order to test the question whether the fish, when offered the 

 choice, tended to select a background in harmony with its own 



