Free swiming larvae are produced during the lifetimes of:

Explanation

Free-swimming larvae are produced during the lifetimes of some annelids, particularly in the class Polychaeta. Annelids are segmented worms, and the class Polychaeta is the largest and most diverse group within the phylum Annelida.In many polychaete species, the life cycle includes a larval stage known as the trochophore larva. The trochophore larva is a free-swimming, planktonic larval form that hatches from fertilized eggs. It is typically ciliated and has a ring of cilia around its body, which it uses for locomotion and feeding. The cilia create a characteristic rotating band, resembling a "trochus," hence the name "trochophore."