112 THE LIFE OF CRUSTACEA 



coloured in various shades of brown, green, or red, 

 or they may be " blotched," ''barred," or "lined," 

 with colour. These different varieties are generally 

 found among sea-weeds, which they resemble in 

 colour and pattern, the " lined " forms, for instance, 

 frequenting finely branched and feathery weed. Like 

 many other protectively coloured animals, they are 

 of sedentary habits, clinging to the weed, and seldom 

 moving by day. If a specimen be removed from its 

 habitat and placed in an aquarium with different 

 kinds of sea-weed, it will take refuge among that 

 which it most closely resembles. It appears that 

 this resemblance in colour-pattern is acquired during 

 the growth of the Prawn, and that a young specimen 

 kept among finely branched sea-weed will acquire the 

 ''lined " pattern, while others, living among coarser 

 weed, become "barred," "blotched," or "mono- 

 chrome." Even in the adult Prawns the colour 

 (though not the pattern) becomes changed in a day 

 or two if they are placed among weed of a different 

 colour — from green to brown, or the like. Within 

 certain limits still more rapid changes of colour take 

 place. If kept in the dark, or if placed on a white 

 background (for example, in a porcelain dish) in the 

 light, the Prawn quickly becomes nearly colourless, 

 by contraction of the chromatophores, a transparent 

 bluish tint alone remaining, due to a substance which 

 diffuses from the chromatophores into the fluids of 

 the body. In natural conditions this phase is assumed 



