Phylum IV: Ctenophora
(Greek, Ktenos meaning comb + phora meaning carrying).
This phylum includes animals (about 100 species) which are simple metazoans resembling the coelenterate jellyfish.
- Exhibits bilateral symmetry.
- Basically diploblastic but the mesoglea contains some muscle cells.
- Ellipsoidal or spherical; transparent body with light rows of comb plates (locomotor organs) on the external surface.
- They possess two solid contractile tentacles which emerge from blind pouches. The tentacles are equipped with adhesive cells (colloblasts) instead of nematocysts.
- They are hermaphrodites. The fertilised egg develops directly into an adult.
Examples of Ctenophora: A. Pleurobrachia; B. Beroe