80 
PACIFIC SCIENCE, Vol. XXI, January 1967 
X 
LU 
a 
z 
LU 
cl 
O 
x 
CL 
o 
I— 
< 
0 
CL 
1 
u 
TIME OF DAY 
Fig. 3. The average daily indices of the darkly pigmented chromatophores of Ocypode ceratophthalma 
when the crabs were maintained in the artificially reversed photoperiod for 4 days on a black or white back- 
ground. 
X 
LJ 
o 
LU 
CL 
o 
X 
CL 
o 
o 
CL 
X 
U 
5 
4 
3 
2 
sand 
sand 
0600 1800 0600 1800 0600 1800 0600 
TIME OF DAY 
Fig. 4. The average daily indices of the darkly pigmented chromatophores in Ocypode ceratophthalma 
when the crabs were maintained in constant darkness for 3 days on a black or a white background. 
