CARNIVOROUS CRUSTACEA AND KING-CRABS 139 



is carried bent forwards against the under side of the thorax, 

 which, together with the head region, to which it is closely fused, 

 is broadened out into a shape varying according to the kind of 

 crab. Swimming having been given up in ordinary cases, com- 

 pensation is provided by the possession of running powers, which 

 may be of no mean order. Regarding the food of Crabs and 

 their part in the economy of nature, Frank Buckland (in Log-book 

 of a Fisherman and Zoologist), in describing a visit to the Brighton 

 Aquarium, speaks as follows: — "Mr. Lawler kindly showed me 

 the ' crabbery ' in the naturalists' room, where these unfortunate 

 things are kept alive in hundreds (they cost one penny for four) 

 for the octopus's dinner. He dropped in a bit of fish among 

 them. In a moment the crabs near rushed towards it. The 

 crabs at a distance, perceiving that ' something was up ', began 

 to run also, just as Londoners will run to a fire, an accident, or 

 any other gratuitous amusement provided for them by circum- 

 stances. In about half a minute there were at least twenty or 

 thirty crabs fastened on to this one bit of fish — a living ball of 

 crabs, in fact. The ball then began to roll. Some crabs fell off 

 the ball on one side, while other crabs climbed up the ball on the 

 other, and then the moving ball rolled away into the other end 

 of the tank, the mass of crabs fighting, pushing, and pinching 

 each other most gloriously." 



" I imagine, therefore, crabs must be very selfish creatures, and 

 that they act on the principle of first come first served. But yet, 

 do we not learn from this scene the great use of crabs? that is, 

 to sweep up and tidy the bed of the ocean. If these active, hungry, 

 and unpaid little scavengers were not in existence, all sorts of 

 dead creatures, fish, shells, &c., would accumulate, and foul the 

 water; but the crab's business and delight is to eat up all he can 

 find. Therefore, I admire the little crabs for doing their duty, 

 even though they do it unconsciously. Crabs are, in fact, the 

 rats of the ocean, ready to eat up all the garbage they can 

 find." 



So far as seizing organs, jaws, and gastric mill are concerned, 

 a crab essentially agrees with a lobster. The group is a very 

 interesting one, and will frequently be mentioned in various con- 

 nections. It may here be remarked that the very numerous 

 species live under the most various conditions. Many are 

 shallow-water forms, others live in deeper water, down to 2500 



