THE LIVING STRUCTURES 135 



Sciences, April, 1915, some results of observation and 

 experiments made at the U. S. Biological Station at Beau- 

 fort, N. C. The work is to be published in full in the bul- 

 letin of the U. S. Bureau of Fisheries. He says : 



"Nearly all fishes simulate their environment to some 

 extent and some flounders do so with remarkable accur- 

 acy and rapidity. It was found that flounders in glass 

 dishes became nearly white on a white ground and nearly 

 black on a black ground. They also assumed approx- 

 imately the colors of all grounds, except red. Fine and 

 coarse patterns in the ground produced correspondingly 

 fine and coarse patterns in the skin, but there was no 

 actual reproduction of patterns. Five days' sojourn in a 

 black pan was required to produce a maximum blackness 

 in a flounder that had been kept two weeks in a white 

 pan, but the change from white to black was effected in 

 two minutes in the same flounder after it had been trans- 

 ferred from one pan to the other. The change from black 

 to white always required an hour or more. Color changes 

 are comparatively slow. Yellow usually predominates in 

 the environment and is assumed more rapidly than green 

 or blue. 



"The skin of flounders contains black and yellow cells 

 called chromatophores and opaque white cells called 

 iridoeytes. The changes in color and pattern are pro- 

 duced by changes in the arrangement of the colored cells 

 and in the extent to which they are hidden by the white 

 cells. These changes are regulated by ocular impressions. 

 Flounders become uniformly white when the head-end 

 is placed on white and the tail-end on black. They be- 

 come black when the head is on black and the tail on 

 white and they become gray when one eye is on white 

 and the other on black. Exposure of one eye to a fine 

 and the other to a coarse pattern produces a combination 



