. Common sponge shapes include vases, tubes,
mushrooms and funnels. Some types of sponge branch
either regularly (as illustrated here) or follow a more
random pattern, but they all share the same major
feature - a cavity inside where the water is sieved
and the food removed. In addition, a growing sponge
may be constrained by its locality, such as a cleft in
, the sea bed rock, or be nibbled by predators, and both
of these factors can have an effect on its overall
form and size