Chordates represent a type of animals characterized by bilateral symmetry and the presence at certain stages of development the following characteristics: the chord, the neural tube, gill slits, endosteal.
Hemichordates represent a group of marine benthic soft-bodied worm-like animals. Hemichordates have a notochord in the anterior part of the body, which is an intestinal appendage that supports the proboscis. In addition to the spinal cord, the hemichordates also have a ventral nerve cord. Next, they differ from chordates in the structure of the heart, nervous system and other features of the internal organization.
Echinodermata is a type of exclusively sea bottom animals. Adult echinodermates are characterized by radial symmetry, while their larvae are bilaterally symmetric.
The similarity between hemichordates larvae (tornaria) and echinodermates bipinnaria larvae suggests that hemichordates are intermediates between echinodermates and chordates.