424 HOMES WITHOUT HANDS. 



"Notwithstanding the unrivaled 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 la- 

 bors are invariably recommenced from the foundation." 



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

 sist 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 molecules. But so perfect is the disposition of the 

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

 gifted with the twofold power of acting on the sucking and the 

 muscular principle. "When the tentacle is about to seize an ob- 

 ject, the extremity is drawn in, in consequence of the sudden re- 

 flux of fluid in its hollow interior; by this movement a cup- 

 shaped cavity is formed, in which the object is securely held by 

 atmospheric pressure ; this power is, however, immediately aided 

 by the contraction of the circular muscular fibres. Such, then, 

 are the marvelous instruments by which these peaceful worms 

 construct their habitations, and probably sweep their vicinity for 

 food." 



There are many species of Terebella, each remarkable for 

 some peculiarity in the structure of its habitation. On the east- 

 em coast of England, the preceding species seems to be more 

 plentiful, and affords a notable instance of the manner in which 

 stubborn materials can be rendered useful. Some of our coasts, 

 however, are plentifully stocked with the Shell-binder Tere- 

 bella {Terebella conchilega), a creature which has earned its well- 

 deserved name from its curious habit of choosing broken shells 

 for the construction of its tube. This being the case, it is evident 

 that the creature will be most abundant on those shores where 

 shells are most plentiful, and that it may usually be found on 

 those parts of our coast where the sand is almost wholly com- 

 posed of shells. 



The tube resembles in texture that of the preceding species, but 

 it is rather firmer, owing to the superior size of the material with 



