Chromatophore Responses — Little 
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0600 1800 0600 1800 0600 1800 0600 
TIME OF DAY 
Fig. 1. The average daily indices of the darkly pigmented chromatophores in Ocypode ceratophthalma. 
The crabs were maintained in the normal photoperiod for 3 days on a white or a black background. The 
chromatophores were indexed every 6 hr. 
0500 1700 0500 1700 0500 1700 0500 
TIME OF DAY 
Fig. 2. The average daily indices of the darkly pigmented chromatophores in Ocypode ceratophathalma. 
The crabs were maintained in the normal photoperiod for 3 days on a white or a black background. 
