HABITS OF THE FOUR-HORNED SPIDER-CRAB. 253 



species " in the aquarium at Naples trimming and plucking off 

 one anotbers hydroids and sponges to use as food. 



Although they would not take beef, I found that the Four- 

 horned Spider-Crabs would, in the absence of seaweeds, some- 

 times eat dead or dying Sabella, and also, though not eagerly, gar- 

 den worms. The Sabella was usually removed from its tube before 

 being given to the crustaceans, but on one occasion there was 

 placed in an aquarium, which contained three adult female 

 Spider-Crabs, a healthy living Sabella in its leathery tube, 

 which was about four and a half inches in length and one six- 

 teenth of an inch in diameter and firmly attached to a shell. 

 A female Pisa which happened to walk over the shell im- 

 mediately seized the Sabella with its two claws and tore the 

 worm into two parts at about an inch and a half from its 

 attachment to the shell, in much the same way that a man 

 would twist and tear a piece of paper across. The Spider-Crab 

 then lifted the loose, larger part in one claw, placed the proximal 

 end in its mouth, and proceeded deliberately to eat along the 

 tube. As fast as the lower end of the tube was bitten off by 

 the Spider-Crab, the worm moved out of its tube through the 

 opening at its upper end. The Spider-Crab now turned the 

 tube round; the worm retreated almost wholly into the remain- 

 ing part of its tube ; * the Spider-Crab then pinched the tube 

 tightly with both its claws in such a way that the worm was 

 held firmly and was unable to move upwards or downwards in 

 its tube, about half the length of the massed gills hanging 

 limply out. It is difficult to decide whether this process of 

 imprisonment of the worm by pinching its tube was an instinc- 

 tive or accidental action on the part of the crustacean. 

 The Spider-Crab again began to eat along its prey, biting 

 through worm and tube together. About half an hour after 

 seizure of the worm the Spider-Crab had disposed of all but 

 about an inch of the upper end of the tube and the gills. It 

 now held out the remainder of the tube at arm's length in the 

 characteristically indifferent manner in which these Crabs hold 

 out unwanted food which they have picked up and are about to 

 throw away again. On looking at the Spider-Crab about three 

 hours later, however, I could not see any trace of the worm or 



"• The Sabella is considerably shorter than its tube. 



