Phylum-Aschelminthes or Nemathelminth :
(i) They are called roundworms as they appear circular in cross section.
(ii) Free living, aquatic, terrestrial or parasitic.
(iii) Organisation of body is organ level.
(iv) Bilaterally symmetrical animals.
(v) They are triploblastic and pseudocoelomate.
(vi) Alimentation is complete with muscular pharynx.
(vii) Sexes are separate.
(viii) Body is covered bv cuticle.
(ix) Fertilization is internal.
(x) Examples are filarial worm (Wuchereria), Ascaris, Hookworm (Ancylostoma) and Pinworm (Enterobius) etc.
