74 Bean and Weed — Coloration of Fishes. 



Preserved specimens of the Pickerel (Esox reticulatus) show 

 very slight differences in color pattern, which is usually more 

 or less of a network of dark lines on a lighter ground, but great 

 differences in its visibility. These differences are probably 

 largely due to the condition of the fish when taken from the 

 water and difference in manipulation in preserving the speci- 

 men. Fishes from clear water usually have the color pattern 

 more pronounced, while those from muddy water, particularly 

 water of a distinctly yellow color, frequently show no traces of 

 the color pattern when first taken and if killed in the preserva- 

 tive immediately will show none. However, if these fish are 

 placed for a few minutes in clear water the color pattern 

 becomes visible, and it may appear in cold water even after the 

 fish has died, showing that the color cells may remain active 

 for a time under favorable conditions. Fishes of this species 

 swimming near the surface in the aquarium show a very strongly 

 marked color pattern. In some of them the reticulations 

 extend entirely over the back, while in others the back is more 

 or less plain dark olivaceous. When these fish are resting on a 

 bottom of clear yellow sand the vertical bars of the reticula- 

 tions tend to disappear and portions of the horizontal bars also 

 become fainter so that the markings resemble wave marks on 

 the bottom. The color of the back becomes plain greenish yel- 

 low, except for the presence of scattered black specks resembling, 

 in color and arrangement, black sand grains in the neighbor- 

 hood. The fish resting near the surface resembles a floating 

 stick covered with spots of light refracted by the small waves. 

 In this species the color changes are not in the nature of a 

 change in color pattern, but simply variations in its intensity. 



In the Yellow Perch (Perca flavescens) the color pattern does 

 not change, but the intensity of the black cross bars is quite 

 variable. Sometimes they are almost invisible and the fish ap- 

 pears to be a clear yellow color, while at other times they are so 

 broad and intense that the fish appears almost black. The 

 ground color changes with the bands from a light yellow to a 

 dark yellowish gray. 



The Sea Robin (Prionotus evolans), the Puffer (Spheroides 

 mar tdatus) , and the Filefish (Alutera scripta) show no change 

 in the color pattern, but considerable changes from golden to 

 grayish in the ground color. Specimens of the Sea Robin 



