15. How is the nervous system
characterized in beings of the
phylum Annelida? How can
one compare cephalization in
annelids to cephalization in
nematodes and
platyhelminthes?

Gap-fill exercise

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Annelids have a system made
of ventral chords and relatively
big nervous concentration in its
portion resembling a
brain.

Nematodes have anterior neural ring
to two neural , a
ventral and dorsal one, while
planarias (platyhelminthes) there
only two small “cerebral”
ganglia from neural chords split.
in annelids thus more
outstanding than nematodes or in
.