TEREBELLA. 205 



ducts, with their slender filaments alternately interwoven in its sides. 

 The tube follows no regular course wherever constructed. 



Sand is collected profusely near the orifice, and quantities of it 

 .swallowed. But I know not whether the heaps appearing, both in the 

 immediate vicinity of this and of other Terebella, are the product of ten- 

 tacular collections, or whether they may not be accumulated from the 

 regurgitation of what has been swallowed. 



Momentary protrusion of the lower extremity is witnessed here, as 

 with the Terebella littoralis. 



Sometimes supervening putrescence of its native element compels 

 this creature to forsake its dwelling. If not, should the observer desire 

 inspection, the tube must be shortened, as much as possible, and the 

 tenant to become a little enfeebled by remaining in the vitiated water. 

 Then, when applying the mouth to one end, while the other remains 

 imrnerged, it may be forcibly blown out. No other expedient can obtain 

 the Terebella entire. 



When this experiment has succeeded, the naked animal coils itself up 

 spirally like a screw, forming six or eight volutions, which absolutely pre- 

 clude a view of its configuration ; and, amidst its contortions, the poste- 

 rior part, remarkably long and slender, is readily ruptured. But a little 

 sand scattered in the vicinity will prevent all inconvenience, by inducing 

 the Terebella to unfold for the purpose of constructing a new habitation. 

 The anterior portion of the body is covered first, and the remainder 

 gradually protected by the advancing edifice. 



Numerous minute white globular capsules are frequently found in 

 vessels containing these Terebellae. Where a specimen had been dislodged 

 from its dwelling, they evidently issued from the very extremity, which 

 had not been entire. Nothing has shewn their definite nature. If they 

 are not animal substances, does any kind of internal formation contribute 

 to modify their form ? Fig. 13. 



This species is common. Individuals may be preserved many 

 months. 



An animal, rather indistinctly described and represented by Mu'ller 

 as the Ampliitrite cristata, seems to have only a single pair of branchiae. 



