Characteristic Features of Chordata
The following unique features help to distinguish
chordates from all other animals of the animal kingdom
(i) Notochord It is a solid, rod-like structure present
on the dorsal side of the body. It is derived from
the mesoderm. Its function is to support and
provide surface for attachment of muscles.
(ii) Nerve Cord It is a hollow tube-like structure
present on the dorsal side of the body. The
anterior end becomes brain while, the posterior
end forms the spinal cord. It coordinates all the
functions of body.
(iii) Pharyngeal Gill Slits These are like paired
openings formed on the lateral sides of the
pharynx that communicate to the exterior.
“They are derived from endoderm.
They help in
respiration.
arc retained throughout the life
in lower chordates and aquatic vcrtebrates and only
during enibryonic stage in all other chordates.
(iv) Post-Anal Tail It is reduced in some adults and
found in majority of chordates. It is a solid, slender
structure formed at the posterior end of the body
after the anus.
I Some Other Features
Apart from the above mentioned features chordates also
possess some other features as given below
(a) A ventral heart and dosed circulatory system is
(b) Haemoglobin is present in red blood corpuscles.
(c) Hepatic portal system is present.
(d) Digestive system is well-developed.
(e) Excretion occurs through kidney.

General features of roundworms are
(i) The body is cylindrical and tapering at both ends.
(ii) No segmentation.
(iii) Bilateral symmetry.
(iv) They have organ system level of organisation.
(v) The anterior end does not form a distinct head.
(vi) There are no locomotory appendages in roundworms.
(vii) The body wall consists of firm, non-living, resistant
cuticle, epidermis and muscle layer.
(viii) These are pseudocoelomates.
(ix) Hydroskeleton is present.
(x) Digestive tract is complete. Respiration occurs bv
body surface.
(xi) Circulatory system is undeveloped. Excretion
through gland cells.
(xii) Sexes are separate. Sexual dimorphism is present’
Fertilisation is internal. There is no asexual
reproduction.
(xiii) Development is direct.