ON ACEPHALA. 393 
We now come to those well known animals the MUSSELs, 
MyYTILvs, L. 
The mussels do not appear to possess a greater general 
or special sensibility than the other testaceous acephala ; 
perhaps, indeed, their sense of touch may be less fine, in con- 
sequence of the absence of tentacular filaments at the edges 
of the mantle. 
Their locomotion is nothing, or very trifling, according to 
some observers, who even assert that the mussel never totally 
changes place, and that the linguiform appendage of their ab- 
dominal mass serves only to spin the different threads of the 
byssus, or to place or fix these threads on submerged bodies. 
According to Reaumur, on the contrary, the mussel can 
change place when it has been accidentally detached by the 
cutting of the fibres of the byssus. He tells us, that in the 
saline marshes on the coasts of the ocean, where the fisher- 
men throw the mussels at hazard, they are found at the end 
of some time, united in packets. By putting them into glass 
vessels, he observed that their mode of locomotion consisted in 
drawing their linguiform appendage out of the shell, curving 
it, hooking it to some bodies, and thus drawing themselves 
towards the point of attachment. It is certain, that in ordi- 
nary circumstances, the mussel does not change place, fixed 
as itis by means of a greater or less number of its fibres, to 
all the surrounding bodies of whatsoever nature they may be. 
When we examine how this fixedness takes place, we find 
that it is by agglutination, each fibre being often a little 
widened at its extremity. The linguiform appendage of the 
foot may also conduce to a similar purpose, and this organ, 
(as has been ascertained by experiment) when cut off, will 
sprout again. 
The mussels undoubtedly feed upon very small animals, 
or their spawn, as is proved by the property which they ac- 
