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 lmed 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 Terebelle 
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. 
Piate XXVI. 
Fic. 10. Terebella ostree. 
. 

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 the figulus. But it is rarely displayed. 
As in the Nereis noctiluca, this apparently results from constraint or 
suffering. Flashes 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 
branchize, 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. 
