THE COLORS OF THE CRAYFISH. 
W. J. KENT. 
Some time has been devoted during the past year to a study 
of the influence of environment upon the colors of the crayfish. 
The work has been confined in a large part to the species 
Cambarus immunis. 
It was first noticed, while studying the habits of crayfish by 
observations in field work, that the color of immunis in nearly 
all cases closely resembled the color of the environment. In 
one small pond of water, where the soil at the bottom was a 
blue clay, the crayfish were all blue in color. In another pond 
with a black, muddy bottom they were all black, and in still 
other places of different colors. But in nearly all cases they 
were of the same color as the environment. 
One exception to this was found with those which w 
These were confined entirely to the shallow water in the small 
streams, and the color was not always similar to the color of 
the environment. The crayfish in all colors except red were 
found almost entirely in the ponds with deeper water and 
muddy bottoms. But it was discovered later that this red 
color in crayfish may be caused by exposure to sunlight. This 
Was first observed while making a microscopic study of the 
pigment, to which most of the color of the crayfish is due. 
This pigment when removed from the crayfish and exposed o 
the sunlight turned red in a short time. The same result 
occurred when all effects of heat were excluded by using 
diffused light and an alum bath. a fish 
The influence of sunlight upon the color of living po " 
Was studied further by experimenting in the laboratory. ded : 
fish of various colors were kept in an aquarium exposed to s x 
light. This is a difficult experiment to carry out. Uny G 
which live in deeper water become strongly ERA E 
can endure only very weak light. It was necessary p 
933 
ere red. 
