Which of the following set of animals are acoelomates without the development of mesoderm?
Acoelomates without the development of mesoderm are diploblastic organisms (Cnidaria and Ctenophora).
Physalia (Cnidaria) and Ctenoplana (Ctenophora) are without coelom and mesoderm.
Taenia (Platyhelminthes) has mesoderm (triploblastic) but lacks coelom (acoelomate).
Wuchereria (filarial worm) and Ancylostoma (hookworm) are triploblastic, pseudocoelomates.