PROTECTIVE COLOEATIOK. 



145 



specimens were invariably ioimd upon dark lava rocks, the 

 lighter ones upon yellowish sandstone." 



Although it has been stated that no insect has the power of 

 rapidly changing its colour in correspondence with the changing 

 environment, certain Crustacea can. The little swimming 

 crab Nautilogmpsus shows temporary changes of colour ; so, 

 too, does a shrimp, Atyoida, recently described by Fritz 



Fig. 14.— Tiee Fiogb 



, Muller ; this crustacean is dark green when among weeds, but 

 becomes pale brown when placed in a glass vessel ; a dark 

 brown individual was placed with a number of others which had 

 a greenish hue ; it assumed their colour directly. 



Frogs also have this power of colour change ; it is well seen 

 in the little tree frog {Hyla arborea) of Europe, which is 

 green when among leaves, and browner when upon stems ; 

 this colour change appears to have an obvious bearing upon 



the habits of the creature. Mr. Ponlton surmises that the 



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