Sponges

grow spontaneously either attached to a rock or on
sea-beaches, and they get their nutriment in slime: a proof of this
statement is the fact that when they are first secured they are
found to be full of slime. This is characteristic of all living
creatures that get their nutriment by close local attachment. And,
by the way, the close-textured sponges are weaker than the more openly
porous ones because their attachment extends over a smaller area.

It is said that the sponge is sensitive; and as a proof of
this statement they say that if the sponge is made aware of an attempt
being made to pluck it from its place of attachment it draws itself
together, and it becomes a difficult task to detach it. It makes a
similar contractile movement in windy and boisterous weather,
obviously with the object of tightening its hold. Some persons express
doubts as to the truth of this assertion; as, for instance, the people
of Torone.