TEREBELLA. 201 
This creature constructs a dwelling of comminuted shell exclusively, 
in preference to all other materials, and is enabled, by the strength of the 
tentacula, to avail itself of large fragments. In the natural state, it 
generally takes shelter within some capacious empty shell, such as a valve 
of the Venus islandica, there to establish its edifice ; and it likewise often 
winds the tube over the surface. But many other situations are taken, 
sometimes those very inaccessible, such as amidst groups of the Tubularia 
indivisa, whence its artificial casement is inextricable. On all occasions 
this tube is formed of irregular and unequal fragments, and lined with 
the silky matter from an exudation of the animal. 
The Terebella may be induced to exercise its architectural faculties 
by diminishing the light during day, as if night were approaching. If 
supplied with different coloured fragments of shell, a variegated tube in 
bands, or otherwise constructed, may be obtained. A beautiful edifice 
is constructed of the shivered pearly interior strata of oyster shells. Thin 
fragments are preferred to thick, but there is no evident discrimination 
of suitable dimensions, as in the course of the work portions very large 
are united to those very small. If the Terebella be restricted to the more 
transparent fragments, a better view of itself within is afforded. 
A specimen having been dislodged from its tube, and committed to 
a vessel containing a few shelly fragments, some sand, and a number of 
small Venetian beads, it employed the whole indiscriminately in fabri- 
cating a new dwelling. But another, supplied with a quantity of sand, 
together with a number of the same kind of beads, rejected the latter, 
confining itself to the sand alone in constructing its edifice. It was not 
a vigorous specimen. 
In default of comminuted shell, the Zerebella conchilega will build a 
tube exclusively of sand. 
By eliciting the propensities of this animal, the observer may have 
much agreeable and interesting entertainment. 
If dislodged from its dwelling in a vessel of pure water, the Tere- 
bella profits by the earliest provision of fresh materials to construct ano- 
ther. While this is conducted up the side of a vessel, the tentacula, 
those essential mechanical auxiliaries, are busily employed. A silky ten- 
2c 
