ADJUSTMENT OF FLATFISHES 439 



then returned to the larger jar used previously (20 cm. diameter, 

 with black walls and gravel bottom), but the maximum gravel 

 effect now persisted for two days, when the fish was again removed. 



Later, this same specimen was put into another jar (20 cm. 

 diameter) having a black bottom and white walls. After five days 

 (no observations being made in the meantime) the fish was of a 

 "pale brown or buff, with pale spots still lighter" (fig. 9c). My 

 record says: ''not only not black, but not a dark fish." 



The animal was next transferred to a jar of the same size with 

 bottom and walls both black. Within less than a day there was a 

 verj^ pronounced change: "Fish so dark and so devoid of conspicu- 

 ous markings as to be pretty well concealed in jar. Not noticed 

 at first" (fig. 9d). The transfer was again made to the white- 

 bottomed jar, and back again to the all-black one, with similar 

 results in each case. 



From the records of the two foregoing specimens, as well as of 

 many others, it is quite plain that the bottom, even when it is of 

 very limited area, and largely concealed by the fish itself, may 

 exert a predominant influence in determining the appearance 

 assumed by the latter. On the other hand, it seems plain from the 

 later behavior of the second of these specimens that the vertical 

 wall may also exert an important influence upon the animal. A 

 comparison of fig. 9c and fig. 9d will sufficiently illustrate this 

 point for the present. This entire question was much more search- 

 ingly tested with Lophopsetta maculata (see below) . 



In order to determine whether a surface directly overhead 

 would have any effect upon the color-pattern of Rhomboidichthys 

 specimens were placed in the large tank (p. 427), lighted from be- 

 low by means of a mirror. A plate of opaque white glass, of the 

 same size as the bottom of the tank, was covered with small, 

 irregular blotches of black paint. Four corks, 35 mm. long, were 

 fastened to the painted surface of this plate, one near each corner, 

 and served as legs when the contrivance was placed at the bottom 

 of the tank. In this position, the spotted side faced downward, 

 at a distance of about 3 cm. above the eyes of the fishes. 



The three specimens used in this experiment had all been unmis- 

 takably influenced by this spotted plate when this was placed 



