CRUSTACEA 169 



and the question has often been discussed as to whether 

 these are hooked on by accident, or purposely placed by 

 the crab. 



The answer is by both methods. As the crab crawls 

 among weeds, bits, of course, do get hooked on, but there 

 is constant attention on its part to the completeness of 

 this disguise, and the tips of the claws are nearly always 

 busy picking up and attaching fragments, and this is done 

 with much care and deliberation. 



It may have been noticed, or may henceforth be, that in 

 this family the claws are so curved that their tips can 

 reach any part of the back, this affording an accomplish- 

 ment not possessed by any other crustaceans. 



In the absence of sea-weeds these crabs bury in shell- 

 gravel or loose shingle, to the level of the edge of the cara- 

 pace, then pile material on their backs. 



Captive specimens in the aquarium of the Biological 

 Station at Jersey were very amusing in this respect. The 

 bottom of their tank was shingle, into which they would 

 half bury themselves. Then, carefully, a claw would reach 

 out for a little pebble, which would be placed on the back, 

 the spines keeping it from slipping, then there would be a 

 pause, to ascertain if all was right ; if the stone slipped a 

 little it \vas gently pushed or lightly tapped until it was 

 safe ; then more stones would be added, until a pile a couple 

 of inches each way was formed. Then, as a rule, the lot 

 would topple over, and the work would recommence with 

 a display of very enviable patience. 



The crab's attempts to keep the body perfectly steady 

 while the claws were at work were exceedingly ludicrous. 

 This species is shown in Figs. 74 and 75. 



Closely allied to Maia is the " Four-horned Spider Crab " 

 (Pisa tetraodon Figs. 76 and 77). This is smaller, more 

 rounded, and less spiny. The male is about an inch and a 

 half across. The claws are largely developed in the male, 



