Animals are divided into two groups based on alimentary canal.
(i) Parazoa: All the animals which do not have alimentary canal are called Parazoa. Animals of the order Porifera are Parazoa. For example, Cycon (Scypha gelatinosum), Spongilla (Spongilla lacustris), Cliona (Cliona celata) etc.
(ii) Enterozoa: All organisms having alimentary canal are called Enterozoa. Enterozoa are animals of the order Annelida, Arthropoda, Nematoda, Platyhelminthes, Echinodermata, Cnidaria, Mollusca and Chordata. Asexual reproducers and sexual reproducers.