This could mean several things. For one, the root of the Bilateral, to which “we” belong, sees one major branch being the acoelomate “worms,” and many of the phyla on the other branch are are worm-like. Also, the animals share at least one worm-like stage in development, the gastrula.
Work Step by Step
Skim the chapter, especially Fig. 32.11, and look for common worm-like features or ancestors to use as the basis for your answer.