202 THE COLOURS OF ANIMALS 



Adventitious warning colours 



Under this head we may include a few very in- 

 teresting cases in which palatable animals make use 

 of others which are specially defended and conspicuous 

 in order to gain protection. Such a method of defence 

 bears the same relation to Warning Colours as the 

 examples of Adventitious Protection and Colouring 

 bear to true Protective Eesemblance (see pp. 76-80). 



A mollusc which encourages a dense growth of 

 algae upon its shell is defended by Adventitious Pro- 

 tective Eesemblance; if, however, the algae were 

 brilliantly coloured and nauseous or poisonous, the 

 example would fall under Adventitious Warning 

 Colouration. 



Professor Romanes ^ brings forward examples of a 

 most interesting association of crabs with sea- 

 anemones. He quotes from Mobius ^ the remarkable 

 case of * two crabs belonging to different genera which 

 have the habit of firmly grasping a sea-anemone in 

 each claw, and carrying them about ; ' also from P. H. 

 Gosse ^ the fact that when the sea- anemone {Adamsia 

 'palliata) is removed from its position upon the shell 

 of the hermit crab {Pagurus Prideauxii), which in- 

 variably carries it, the crab 'always took it up in 



• Animal Intelligettce, International Science Series, pp. 233-34. 



* Beitrdge zur Meeresfauna der Insel Mauritius. 

 « Zoologist, June 1859, pp. 6580-6584. 



