THE BRISTLE-WORMS. 121 



when alarmed or injured. The worm is very common, and 

 though not particularly active in its movements, is an 

 interesting little creature. 



The big sea-snake (Linens marinus) is usually only to be 

 found far out on the rocks near low-tide mark, but is there 

 common enough. It is a 

 splendid animal, varying in 

 length from about three feet 

 up to many yards, but not 

 much thicker than the boot- 

 lace to which fishermen 

 compare it. The colour is 

 usually said to be black, 

 but in reality in life is a 

 beautiful changing purple, 

 soft and velvety in tint. 

 The animal, like all its 

 allies, is somewhat slimy, 

 and has a habit of coiling 



itself in strange knots, but FIG. 40. Linens marinus, the sea-snake. 



it is nevertheless exceed- fc, head with slits, 



ingly beautiful. Readers of Kingsley's Glaucus will perhaps 

 protest at the adjective, remembering the pages of energetic 

 vituperation which the author hurls at the unfortunate 

 animal, but I cannot think that anyone who studies it 

 without prejudice can fail to be struck by the beauty of the 

 animal. 



Like other ribbon-worms, Linens has head-slits at the 

 sides of the head, and a long proboscis. It lives well in 

 confinement, but usually conceals itself under stones, or in 

 sand agglutinated by its own secretion. Like all its allies, 

 it is extremely brittle, breaking into pieces on the slightest 

 provocation. It is in consequence very difficult to obtain 

 perfect specimens for preservation. 



The last group of "worms" we shall mention is the 

 Polyzoa curious, much modified forms, which live in colonies, 

 and are not unlike "zoophytes." The commonest is Flustra, 

 the sea-mat, which is very common in a dry state on the 

 beach, and is often called a seaweed. These dried specimens 

 are in reality merely the houses of the dead worms. A 

 close examination of a piece of sea-mat will show that it is 



