UNIVALVES. i8k 
nished with food from the sea-water, which he receives, 
like the Actinic, through the medium of several small 
tentacule. 
Teredines, turn readily in their respective shells; 
to which they merely adhere, by means of a slight 
connexion at one particular part; and this arrange- 
ment is evidently designed to prevent the tubes from 
being disturbed by the motion of the inmates, which 
resembles that of boring. As the T'eredo gigantea, 
or Great Bifurcated Borer, burrows in the mud, on 
which he cannot be supposed to subsist, a question 
has arisen, whether the 7’. navalis receives any support 
from the wood which he destroys; or is solely sup- 
plied with food from the sea. The latter opinion is 
now generally adopted. It appears, on a close in- 
vestigation, that the sawdust received by the animal, 
does not experience the slightest change; as when 
exposed to the action of fire, it emits the odour of 
wood, and forms a charcoal, which readily consumes 
into white ashes, in every respect resembling those 
produced by a vegetable substance. 
When the hull of a vessel continues for any length 
of time in water, the Teredines appropriate it to 
their use. They commence their operations by per- 
forating the softest parts of the wood, and as they 
have seldom at this period attained their full growth, 
the perforations are frequently so small as to be 
