186 TEREBELLA. 



or Annelides. The tentacula and the branchiae 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- 



