Madisons
The Phylum Cnidaria
The Phylum Cnidaria
Etymology:- From the Greek knide for nettle.
Characteristics of Cnidaria:-
1)Radially Symmetrical.
2)Body multicellular, few tissues, some organelles.
3)Body contains an internal cavity and a mouth.
4)Two different forms exist, medusa and polyp
5)Reproduction is asexual or sexual.
6)Has a simple net like nervous system.
7)Has a distinct larval stage which is planktonic.
8)Lives in aquatic environments, mostly marine.
9)Mostly carnivorous otherwise filter feeders.
10)May have a minimal skeleton of chiton or calcium carbonate.
The Cnidaria come in two basic forms, a 'Polyp' form typified by the Sea Anemones and a 'Medusa' form typified by Jellyfish. Generally speaking Polyps are tube shaped and sedentary with a ring of tentacles around the mouth, Medusae are umbrella or bell shaped, free living and have a central projection on the inside of the umbrella which supports the mouth and their tentacles around the rim of the umbrella.