186 TEREBELLA. 
or Annelides. The tentacula and the branchize are compressed and 
contracted about the head like a brush, and as the animal becomes very 
soon exhausted by such unnatural exertions, it soon sinks to the bottom. 
Should a quantity of sand be now scattered from above, the tentacula, 
relaxing speedily, extend to sweep the vessel clean, so that in the briefest 
interval, not a particle remains within their reach. The whole have 
been collected for employment in the construction of a new artificial 
dwelling for sheltering the naked body of the architect. Permanent ex- 
posure to the light, or to the air, is pernicious. 
The artifice, the selection of materials, and the expedition demon- 
strated by this creature, are truly admirable ; nor is it a small gratifica- 
tion to the curious, that all its qualities may be displayed before them. 
Should a tube be already constructed on the side of a glass vessel 
wherein a specimen has had a permanent abode, the inhabitant is found 
lurking within in the earlier part of the day ; only the extremities of the 
tentacula protrude beyond the orifice ; and so they remain till towards 
noon. But scarcely has the sun passed the meridian, when the animal 
begins to, be restless. Between four and five the animal has risen up- 
wards, the tentacula extending with the approach of evening, and after 
sunset, they are in the greatest activity. They are now let down from 
the orifice like so many slender cords, each seizes on one or more grains 
of sand, and drags up its burden to the top, there to be employed at the 
summit of the tube according to whatever service is requisite. Should 
any of the ladening slip its hold, the same organs search eagerly after 
it at the bottom, to be seized and raised to the top anew. 
Such operations are protracted during several hours, though with- 
out any visible additions to the tube. Nevertheless, on resuming inspec- 
tion next morning, a surprising prolongation will be discovered ; or, in- 
stead of an accession of the same description, the orifice is sometimes 
surrounded by forking threads of sandy particles agglutinated together. 
The architect has now retired to repose ; but, as evening comes, its 
activity is renewed, and against sunrise, a further prolongation has 
augmented its dwelling. 
All these are nocturnal labours. Such, indeed, are the habits com- 
