Which phylum is known as sea walnuts or comb jellies?

What is the function of the comb plates present in Ctenophora?

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.

The ciliated comb plates in $Pleurobrachia$ are meant for

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

All organisms of this phylum exhibit bioluminescence.