544 



THE WONDER OF LIFE 



of a shore- crab is directly influenced, while the shell is 

 being formed after a moult, by the dominant colour of the 

 immediate environment. 



There can be no doubt that certain colour-reactions 

 which follow reflexly and necessarily often look as if they 



FIG. 87. Much branched chromatophore of a prawn, Praunus flexuoxus. 

 (After Degner.) The pigment flows out along the root-like branches 

 or contracts centripetally. The chromatophore seems to arise 

 from a combination of cells a syncytium. 



should be advantageous, but it is difficult to give direct 

 proof of this. One of the prawns, Palcemon treillianus 

 studied byFrohlich (1910) is blue] or green by day,|when 

 its red chromatophores are strongly contracted, and reddish- 

 brown by night, when the red chromatophores expand, 

 one is put into a white porcelain vessel it becomes 



