70 Bean and Weed — Coloration of Fishes. 



Mouth Black Bass changed in less than two seconds, so that the 

 band was entirely invisible and the fish appeared to be a Small 

 Mouth Black Bass. In preserved specimens of both species the 

 color, except for the black lateral band, is plain; that is, there 

 are no mottlings or marmorations, but in the aquarium, where 

 the fish are so used to seeing visitors that they pay no attention 

 to their presence, the color may be seen to change from plain 

 olivaceous without the black lateral band to plain olivaceous 

 with such a band, or to a mottling of light and dark green with 

 or without the black band. The Large Mouth Black Bass when 

 showing the mottled color usually shows the black band ; speci- 

 mens of the Small Mouth Black Bass usually do not show the 

 black band and the mottlings have a greater tendency to appear 

 as dark cross bars. It is difficult to determine the exciting 

 causes of these changes as fish hiding in crevices of the rocks 

 will show both colorations and fishes swimming show both color 

 patterns. It appears, however, that fish swimming freely or 

 hiding in rather dark holes have a greater tendency to exhibit 

 the plain coloration, while those resting on the bottom or swim- 

 ming close to the rocks at the side of the aquarium have a 

 greater tendency to show the marbled or mottled color pattern . 



Preserved specimens of Tautog (Tautoga onitis) are usually 

 nearly plain black but with more or less distinct vertical light 

 and dark bars of about equal width. In the aquarium they 

 show remarkable variations of these two color patterns. When 

 swimming freely the color is usually plain black and when rest- 

 ing on the bottom or at the sides of the aquarium the bright 

 pattern is visible. However, these colors are not constant and 

 swimming fish may be seen showing the bars while those resting 

 on the bottom show the dark color. The color changes are 

 frequently very rapid. We have seen a fish swimming in a 

 vertical circle about two feet in diameter showing the bright 

 coloration only near the bottom of the aquarium and the black 

 color in the upper half of the circle at each turn. 



In the New York Aquarium at Battery Park notices are posted 

 in front of certain tanks containing some of the tropical angel 

 fish, calling attention of visitors to rapid changes in color and 

 color pattern of this fish. These changes are truly marvelous. 

 Waves of blue starting at the head pass to the tail and disap- 

 pear. While one is watching the fish the color will become all 



