THE SHELL-BINDER TEREBELLA. 40? 



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

 muscular principle. When the tentacle is about to seize an object, 

 the extremity is drawn in, in consequence of the sudden reflux of 

 fliud 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 con- 

 traction of the circular muscidar fibres. Such, then, are the 

 marvellous 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 eastern 

 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 

 composed 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 

 which it is built. Generally the fragments of shell are very 

 small, no larger, indeed, than those of which the well-known 

 sheR-sand is composed. But, in many instances, the Terebella 

 has been known to choose shells in an entire state, and thus to 

 give its tube a very extraordinary aspect. 



The process of tube-making is conducted %vith much rapidity. 

 Supposing that, as is often the case, a storm has arisen, and 

 washed away the projecting portion of the tube, the Terebella 

 sets to work to make a new portion in lieu of that which 

 has been destroyed. Spreading out its long and delicate ten- 

 tacles in all directions, it brings the materials towards its mouth, 

 and always apportions the number of tentacles employed to the 

 load which is to be carried. Having brought the materials 

 within reach, it arranges them in regular circles, agglutinating 

 them together with some secretion which has the propertj' of 



DD 2 



