Mussel and Cockle. 93 
grounds, specially cared for and protected. As a 
ship by its cable, so commonly the Mussel, by its 
bissus or beard, is made fast to its anchorage- 
ground, be it pebbly or sandy beach, or jutting 
rock. Sometimes, however, the mollusk travels; 
and this is how it manages to do so: it has a stout, 
fleshy foot, in shape something like that of a 
chubby child, and this it can advance about two 
inches beyond the edge of the shell, then fixing 
the point of it to a piece of rock or any other 
body, and contracting it, the shell is drawn onward, 
and sure, though slow, progress is made in any 
desired direction. The Pinna, as the marine Mussel 
is called, has a foot which is cylindrical in shape, 
and has at the bottom a round tendon, almost as 
long as itself, the use of which appears to be to 
gather in and retain the numerous threads with 
which, when inhabiting the shores of tempestuous 
seas, it lashes itself fast to the fixed objects around; 
these threads are fastened at various points, and 
then drawn tight by the animal, whose instinct 
teaches it that its brittle shell would soon be 
broken in pieces, if suffered to roll hither and 
thither at the mercy of the waves. 
The Mussel has a very curious method of pre- 
paring its cable for this service; it is not woven, 
cf 
