190 TEREBELLA. 
discover how it proceeds to rectify so serious a disaster. The light of 
day seems obnoxious to all the race. 
On removal of an intermediate portion of its tube, the tenant im 
repairing the breach prolonged the lower part upwards, so as to preserve 
the regular course of communication, uniting the new work with the 
older fabric above. 
A series of experiments might tend to ascertain the precise extent 
of the instinctive faculties among the architectural tribes, and whether 
there is any approximation to that kind of retrospective reasoning gene- 
rated by experience ; also how their labours are exercised, if according 
to circumstances. 
Nothing has supported any conjectures relative to the food of this 
genus. All have rejected animal substances. The whole vermicular 
race not known to subsist on prey, seem to derive most part of their 
sustenance from sandy or earthy matter. The timidity of the Terebella 
effectually precludes it from attempting the capture of living prey. It 
is always readier to retreat than to advance. The smallest and most de- 
fenceless creature might, apparently, repell its attacks. 
Everything, indeed, is secured by the tentacula, animal or vege- 
table fragments, particles of shell, and the like, not for food, but to be 
incorporated with the wall of the dwelling. Something of earthy con- 
sistence occupies the intestinal organs. Thus it may resemble the other 
vermicular species, swallowing earth as the source of aliment, or sand, to 
be reposited in a special reservoir. 
Frequent renovation of its native element is essential for the salu- 
brity of the Terebella, as well as for the vigorous exercise of its functions. 
With moderate precaution specimens have survived six months in con- 
finement. 
The healthy aspect, and the strength and plumpness of the body, 
argue copious subsistence in the natural state. 
Mutilation of the body is often concomitant on the violent contor- 
tions of the Terebella, when dislodged from its tube. Large. portions of 
the posterior part seem easily ruptured ; the tentacula, also separating 
by force or accident, continue a long time demonstrating vitality. Yet 
