As nouns the difference between hemichordate and cephalostatin

is that hemichordate is any of many marine worms, of the phylum Hemichordata, that have a primitive notochord while cephalostatin is a steroid dimer, isolated from a hemichordate of the genus genus: Cephalodiscus, that induces apoptosis.

As an adjective hemichordate

is of, pertaining to, or characteristic of these animals.