Biologic evolution

Consideration of method of moving mussel.
The method of moving the mussel is two.
One is a method of putting the string by using "" and the little movement.

Another is a method of throwing far away by exhausting the internal
organs part in the shell, lightening the weight of the shell, and using
the wave etc. and the movement.
The mussel in the photograph is the one in the state to live.
There is a body in the shell.