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and at others have several inches of their tubes 

 exposed. In the one case, they must work their 

 way speedily to the surface ; in the other, they 

 must dive deeper below it. The manoeuvres of 

 the terebella are best observed by taking it out 

 of its tube and placing it under water upon sand. 

 It is then seen to unfold all the coils of its body, 

 to extend its tentacula in every direction, often 

 to a length exceeding an inch and a half, and to 

 catch, by their means, small fragments of shells, 

 and the larger particles of sand. These it drags 

 towards its head, carrying them behind the 

 scales which project from the anterior and lower 

 part of the head, where they are immediately 

 cemented by the glutinous matter which exudes 

 from that part of the surface. Bending the head 

 alternately from side to side, while it continues 

 to apply the materials of its tube, the terebella 

 has very soon formed a complete collar, which it 

 sedulously employs itself to lengthen at every 

 part of the circumference with an activity and 

 perseverance highly interesting. For the pur- 

 pose of fixing the different fragments compactly, 

 it presses them into their places with the erected 

 scales, at the same time retracting the body. 

 Hence the fragments, being raised by the scales, 

 are generally fixed by their posterior edges, and 

 thus overlaying each other, often give the tube 

 an imbricated appearance. 



Having formed a tube of half an inch, or an 



