Write a short note on: Coelom.

(N/A) The $Coelom$ is a body cavity which is lined by the mesoderm.
$1$. Based on the presence or absence of a cavity between the body wall and the gut wall,animals are classified into three types:
$2$. $Acoelomates$: Animals in which the body cavity is absent (e.g.,Platyhelminthes).
$3$. $Pseudocoelomates$: Animals in which the body cavity is not lined by the mesoderm,instead,the mesoderm is present as scattered pouches in between the ectoderm and endoderm (e.g.,Aschelminthes).
$4$. $Eucoelomates$ (True Coelomates): Animals possessing a true body cavity that is lined by the mesoderm on all sides (e.g.,Annelida to Chordata).