192 Dwellers of the Sea and Shore 



evolved the habit of planting on their bristly backs 

 all sorts of marine vegetation and low forms of animal 

 life such as hydroids and sponges. The result is that 

 they are sometimes so completely hidden by these 

 growths that their presence is indistinguishable in nor- 

 mal situations. In gathering material, therefore, I 

 have been deceived into attempts to appropriate the 

 private property of these animals; and my eiforts to 

 detach some likely-looking specimen from its base 

 brought a pair of puissant pincers to bear upon my 

 hand. These crabs are sluggish in their movements, 

 which perhaps accounts for their habit of disguising 

 themselves, and although some individuals have legs 

 that spread over a foot they succeed in masking their 

 appearance very effectively. 



The plants and other growths which they gather for 

 masking purposes seem to be selected with an extraor- 

 dinary degree of acumen. They will transplant only 

 such organisms as will not suffer permanent injury by 

 being torn apart. That the growths on their carapaces 

 are placed there by intention and do not affix themselves 

 spontaneously, and that the spider crabs are quite as 

 able to denude as to adorn themselves, becomes readily 

 obvious if we place one in a tank or other environment 

 which contains masking material of a different kind or 

 color than that already covering the animal. If the 

 creature is masked with colors that contrast with its 

 surroundings, it will remove its coat and replace it with 

 one in harmony with the new locality. In making this 

 change, the crab laboriously picks off with one of its 

 claws whatever colors are not in keeping with its situa- 

 tion, the chelipeds being well adapted by their length 



