Chapter 31, Problem 4TYK

Summary Introduction

Introduction:

Cnidaria and Ctenophora, the two phyla of soft-bodied organisms, are radially symmetrical (the parts of their body are arranged regularly around the central axis, like the spokes of a wheel) and lack organ systems and coelom. The phylum, Cnidaria (knife: stinging nettle) has nearly nine thousand species. Cnidarians have unique cells in their epidermis called cnidocytes, which is armed with a stinging nematocyst.