TEREBELLA. 



147 



and dies in its turn. And so on in both portions, 

 the anterior perishing from the wound towards 

 the head, and the posterior portion from the 

 wound towards the tail. The latter portion, 

 indeed, loses the power of locomotion altogether, 

 and can only twist and wriggle about on the spot 

 where it is placed. If only a portion of the tail 

 end be cut off, the remaining part has some- 

 times suificient strength to heal the wound, and 

 the creature survives ; but the wounded portion 

 is not capable of producing a fresh tail, or even 

 of forming a single fresh ring. 



If the sand or stones be carefully examined at 

 low water, certain curious objects will often be 

 found between tide-marks, sometimes existing 

 singly, but generally living in societies. One of 

 these objects is represented on plate f, fig. 2. It 

 is a tube composed of innumerable fragments of 

 shell, or sometimes of entire shells, if they are 

 sufficiently minute, grains of sand, and other 

 similar substances, agglutinated together by a 

 secretion that is poured from the surface of 

 the body, and which soon hardens into a tough 

 membranous substance. The mouth of the tube 

 is adorned with a fringe, which is composed of a 

 number of much smaller tubes formed from the 

 same substances, and in the same manner, as the 



l2 



