402 HOMES WITHOUT HANDS. 



to its walls, the orifice will be 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 again at sunrise a further 

 prolongation has augmented the extent of its dwelling. 



" At first sight, the numerous tentacula seem only so many 

 long, cylindrical, fleshy threads, of infinite flexibility. 



" On examining them, however, more attentively, we see that 

 in exercising their special function, the surface which is applied 

 to the foreign objects becomes flattened into twice or thrice its 

 ordinary diameter ; and while conveying the sandy materials to 

 the tube, these are seized and retained in a deep groove, which 

 almost resembles a slit ; in fact, the tentaculum becomes a flat, 

 narrow riband, folding longitudinally in different places to hold 

 the particles securely. 



" Although these organs, when contracted, are collected into a 

 brush scarcely double the thickness of the animal's body, so 

 enormous is their extensibility, that tliey can be stretched out to 

 the length of four inches, or half the length of the body, thus 

 sweeping the area of a circle eight inches in diameter. 



" A thin internal coating, resembling silk, lines the whole tube, 

 and at the same time serves as a real cement to unite and 

 strengthen its innumerable parts. This silk-like material is 

 derived from a glutinous slime, which exudes from the surface of 

 the body of the Terebella. 



" Kotwithstanding the unrivalled expertness and expedition 

 with which this Annelidan advances its work, it has never been 

 observed to resume possession of its tube when once forsaken. To 

 obtain the shelter of a new dwelling in place of the old, its 

 labours are invariably recommenced from the foundation.'' 



" In Terebella nebulosa," writes Dr. "Williams, " the tentacula 

 consist of hollow, flattened tubular filaments, furnished with strong 

 muscular parietes, each tentacle forming a band which may be 

 rolled longitudinally into a cylindrical form, so as to inclose a 

 hollow, cylindrical space, if the two edges of the band meet, or a 

 semi-cylindrical space, if they imperfectly meet. This inimitable 

 mechanism enables each filament to take up and firmly grasp, at 

 any point of its length, a molecule of sand, or, if placed in a linear 

 series, a row of m.olecules. But so perfect is the disposition of the 

 muscular fibres at the extreme free end of each filament, that it is 



