2G4 THE INHABITANTS OF THE SEA. 



In most of the wandering annelides, each segment is pro-, 

 vided with variously formed appendages, more or less developed, 

 serving for respiration and locomotion, or for aggression and 

 defence ; while in some of the least perfect of the class, not a 

 trace of an external organ is to be found over 

 the whole body. The great Band-worm. 

 (Nemertes gigas) is one of the most remark- 

 able examples of this low type of annelism. 

 It is from thirty to forty feet long, about 

 Ap r0 Mousef ea half an inch broad, flat like a ribbon, of brown 

 or violet colour, and smooth and shining like 

 lackered leather. Among the loose stones, or in the hollows of 

 the rocks, where he principally lives on Anomiae, — minute shells 

 that attach themselves to submarine bodies, — this giant worm 

 forms a thousand seemingly inextricable knots, which he is con- 

 tinually unravelling and tying. When after having devoured all 

 the food within his reach, or from some other cause, he desires 

 to shift his quarters, he stretches out a long dark-coloured 

 ribbon, surmounted by a head like that of a snake, but without 

 its wide mouth or dangerous fangs. The eye of the observer 

 sees no contraction of the muscles, no apparent cause or instru- 

 ment of locomotion; but the microscope teaches us that the 

 Nemertes glides along by help of the minute vibratory 

 cilise with which his whole body is covered. He hesitates, he 

 tries here and there, until at last, and often at a distance of 

 fifteen or twenty feet, he finds a stone to his taste ; whereupon 

 he slowly unrolls his length to convey himself to his new resting 

 place, and while the entangled folds are unravelling themselves 

 at one end, they form a new Gordian knot at the other. All 

 the organs of this worm are uncommonly simplified ; the mouth 

 is a scarce visible circular opening, and the intestinal canal ends 

 in a blind sack. 



Nature has not in vain provided the more perfect annelides 

 with the bristly feet, which have been denied to the Nemertes 

 and the sand-worm. Almost all of them feed on a living prey, 

 — Planarias and other minute creatures — which they enclasp 

 and transpierce with those formidable weapons. Some, lying in 

 wait, dart upon their victims as they heedlessly swim by, seize 

 them with their jaws, and stifle them in their deadly embrace; 

 others, of a more lively nature, seek them among the thickets of 



