168 THE DISTRIBUTION OF 



are eaten by the natives as food. The portion of the 

 worm which remains behind in the coral reefs regener- 

 ates the missing segments, and a year later the process 

 is repeated. A similar process is suggested in certain 

 British annehds, and is a device to ensure that the 

 eggs are carried to a distance from the parent. 



The httoral annehds show many beautiful adapta- 

 tions to shore Hfe. We can only name the sea-mouse 

 (Aphrodite), which Hves buried in mud ; Serpula, 

 which secretes lime from the sea water and fashions 

 a tubej which it attaches to rocks or to the hard parts 

 of other animals or to weed ; TerebeUa, which builds 

 up tubes from the sand, and implants them deeply in 

 the sand so that it is safe from the wash of the waves ; 

 a Nereis, which Hves inside the shell inhabited by 

 a hermit crab, and thus finds protection from its 

 enemies, and so forth. Very many of these anneUds 

 are greatly prized as food by fishes, and it is their 

 abmidance in the shore waters that attracts so many 

 fish there. 



Very many of the echinoderms also are UttoraJ, and 

 manifest obvious adaptations to this mode of life. The 

 sea-urchins burrow in the sand or mud, or else cKmb 

 about the rocks by means of their suctorial tube feet. 

 Starfish and brittle-stars similarly clamber over the 

 bottom, while the holothurians either five buried in 

 the sand or attach themselves by their tube feet. 



Not a few unsegmented worms are Httoral, a pretty 

 example being the turbeUarian caUed Convoluta, which 

 possesses sjnnbiotic algae, a common feature of shore 

 animals of simple structure. 



Perhaps the most interesting forms are, however, the 

 Coelentera, which often show a double adaptation to 

 Httoral and to pelagic Hfe. The fronds of the shore 



