186 THE OCEAN. 



the hindmost pair have the last joint flattened out 

 into a thin but broad oval plate, the edge of which 

 is thickly fringed with fine hairs. This structure is 

 exactly parallel to that by which the foot of a perch- 

 ing bird is modified into the foot of a swimming 

 bird, the surface being dilated into a broad web; or 

 to the wide fringe by which the hind feet of a water- 

 beetle are made such powerful oars; the flattened 

 joint in the present case becoming a paddle, by the 

 stroke of which a rapid motion is obtained through 

 the water. These Swimming Crabs are very vora- 

 cious, preying upon the little shrimps that are nume- 

 rous about the weed, which they pursue and seize 

 with their pincers. Sometimes the Crab remains 

 at rest, but vigilant, until a shrimp swims within 

 reach, when he grasps it with great quickness, and 

 proceeds to devour it by degrees. In doing this, 

 he holds it fast by one claw, while with the other 

 he picks off very daintily the legs and other mem- 

 bers of his prey, putting them bit by bit into hig 

 mouth, until nothing remains but the tail, which he 

 rejects. 



The weed is usually the resort of several small 

 species of fishes, which doubtless congregate about 

 it for the sake of the minute Crustacea that are so 

 abundant. Among them I have found a very in- 

 teresting little species of Toad-fish (Antcnnan'us), 

 whose pectoral and ventral fins project so far from 

 the surface of the body as to expose the joint, and 

 thus take the form of the feet of a quadruped. It 

 usrs these members actually as feet, crawling and 

 pushing its way among the tangled weed by means 



