ZOO 115 Invertebrate Zoology Nematoda. Phylum Nematoda Common name: round worms >20,000 species. Mostly widespread and abundant of all metazoans 90,000.
How do the acoelomates fit in? Porifera unknown common ancestor Cnidaria triploblastic organ level of organization Platyhelminthes protonephridia cephalization.
