§ 3.223 EFFECTORS WITH MOVABLE PIGMENT GRANULES 101 



Light activating LDH 



No LLH secretion 



Reflected light activating some LDH 



Light activating LLH 

 No LDH seaetion 



Light activating LLH only 



Fig. 3-21. Diagram of Ligia, in face view (cf. Fig. 3-20«), to show 

 a method of illuminating separately the dorsal CD), lateral (L) and 

 ventral (V) areas of the compound eyes. Arrows indicate the direc- 

 tion of light falling on the eyes, which are exposed by cutting short 

 the antennae (An.ii). The animals are confined in shallow cells 

 allowing horizontal movement only. Screens, indicated by black- 

 ened areas, prevent the entry of light. Stippling represents the 

 chromatophore reaction to secretion of LLH, L?'§'/a -lightening 

 hormone and LDH, Lz^/«-darkening-hormone. (a) Illumination 

 from above only, (b) Illumination by direct light from below, with 

 reflected light from above, (c) Illumination from below only 

 (Original diagram, based on Smith, 1938). 



