ON ACEPHALA. 413 
or of some resinous gum which they contain; but what these 
woods are, and even whether the assertion itself be true, are 
points not ascertained. It is said that the previous carboniza- 
tion of piles, to the depth of a few lines, will be sufficient to 
protect them completely; but for vessels, the best method 
undoubtedly is coppering the bottoms. 
For the great injury done us by the teredines, there appears 
to be some slight compensation. They are said to constitute 
an article of food with some of the inhabitants of the coasts 
of the Atlantic, and their flesh is reported to be very 
delicate, and of a more agreeable flavour than that of the 
oysters. It is probable, also, that they may have their use in 
removing decayed vegetable matter, serving to somewhat the 
same end at sea, as the éermites, and many other insects, do 
by land. 
According to Seba, who made his observations in Holland, 
certain species of nereides are mortal enemies to the teredines, 
penetrating into their tube and devouring them. ‘The species 
of teredo appear to exist in all parts of the globe. 
We now proceed to the second order of Acephala, or those 
without shells. 
The BIPHORES of the text, THALIA SALPA, &c., are 
curiously constructed animals. ‘These gelatinous, transparent 
mollusca, sometimes free, and sometimes united in long lines, 
or cordons, like fire in consequence of their phosphorescent 
quality, must long ago have attracted the attention of naviga- 
tors. But it must have been somewhat difficult to form an 
exact idea of them, in consequence of their remoteness from 
ordinary conformation. Had they come under the inspection 
of some ancient naturalist, which is very probable, they 
would have been placed among the purgamenta maris, that 
is, in the very numerous section, where old writers placed all 
animals that do not come under the ordinary forms. 
The Salpze float constantly immerged at variable depths in 
