Ctenophoras are exclusively marine,$X$,$Y$ organisms with tissue level of organisation.
$X$ - $Y$

In Ctenophora,the body bears $....$ external rows of ciliated comb plates,which help in locomotion.

Describe the phylum which shows bioluminescence.

Identify the phylum which shows the following characteristics:
$1$. Animals are exclusively marine,radially symmetrical,and diploblastic.
$2$. Body bears eight external rows of ciliated comb plates which help in locomotion.
$3$. Digestion is both extracellular and intracellular.
$4$. Reproduction is only by sexual means.

All organisms of this phylum exhibit bioluminescence.

The property of a living organism to emit light is found in $:-$