Q. What do you mean by Hemichordata ?

Hemichordates re vermiform (worm-like) animals which have few characters like those of the chordates, hence the name hemichordata (hemi : half; chorda : string or cord). Hemichordates belong to the deuterostome branch of the animal kingdom and are enterocoelous coelotnates with radial cleavage. They show some of both echinoderm and chordate characteristics. A chordate plan is suggested by gill-slits in the pharynx and a restricted dorsal tubular nerve cord in the collar region. On the other hand, similarity to echinoderns is shown in (i) larval features and (ii) in having an epidermal nerve net. In this unit you will stildy the type specimen Balarroglossus of the phylum hemicliordat and the tornaria larva which is typically found in its life cycle.