Phylum Ctenophora or Ctenophores commonly known as sea walnuts or comb jellies are exclusively marine, radially symmetrical, diploblastic organisms with tissue level of organization. The body bears eight external rows of ciliated comb plates, which help in locomotion (Figure).
Digestion is both extracellular and intracellular. Bioluminescence (the property of a living organism to emit light) is well-marked in ctenophores. Sexes are not separate. Reproduction takes place only by sexual means. Fertilization is external with indirect development.
Examples: Pteurobrachia and Ctenoplana,