Fig. 3-19. Photographs of the male fiddler crab, Uca piigilator, in 

 the light. The normal specimen on the left is dark ; that on the right 

 had the eyestalks removed 2 hours previously and the pigment 

 has concentrated in the legs; the pallor shows best in the large 

 asymmetric chela. The carapace is too thick to allow the colour 

 change to be seen through it (from Carlson, 1936). 



P'iG. 3-20. Photographs of the head of the sea-slater, Ligta oceanica, 



with the antennae cut off short, (a) Face-view; (b) lateral view of 



the head and eyes, differential illumination of which controls the 



release of chromactivating hormones (from Smith, 1938). 



