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 Zerebella 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 
immerged, 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 Miiller 
as the Amphitrite cristata, seems to have only a single pair of branchie. 
