210 TEREBELLA. 



The special habitation of this creature is a cavity adapted for its 

 body, often in the thickest part of the shell. I have not seen it in any 

 other substance. The cavity is lined with silk, and corresponds with the 

 dimensions of the body ; it may be enlarged by some solvent. There 

 the tenant lurks, protruding its tentacula by a circular aperture, which 

 are always searching around the vicinity, like those of the Terebellse 

 proper. 



Although not dwelling in society, several specimens are occasionally 

 found within narrow limits. At least twelve have been seen displaying 

 their tentacula from the surface of a single shell ; besides which, there 

 were probably some of small dimensions, obscured by adventitious 

 matter. 



PLATE XXVI. 



FIG. 10. Terebella ostrece. 



Besides the peculiarities of the Terebella proper, such as are defi- 

 nitely shewn by the littoralis, figulus, tuberculata, and conchilega, above 

 explained, a brilliant phosphorescence belongs to some of the genus, and 

 particularly to tkejiguhis. But it is rarely displayed. 



As in the Nereis noctiluca, this apparently results from constraint or 

 suffering. Plashes were emitted by a small specimen having left its tube 

 on transference to a different vessel. On replenishing the latter with 

 water, the most copious bright blue refulgence, intermingled with a red- 

 dish flame, streamed from the tentacula and other organs. Apparently 

 the phosphorescent property is diffused over the body, and here the 

 coruscations evidently attended violence. 



Several facts merit particular investigation, such as, whether all 

 branchiae, or the hairs of them, are identically of the same character ; 

 and whether their full complement is original or successively developed. 

 Also, whether the habits of the animal are not affected by age, and from 

 the season of propagation. 



