Many taxa such as the Digenea are normally-hermaphroditic.
Some groups, however, have become dioecious.
Some taxa such as the Nematoda are normally-dioecious.
However, many groups such as the rhabditida have hermaphroditic species.
Acanthocephalan male use an eversible copulatory bursa to grasp the female.
Nematodes have a variety of modifications. Male Trichinella grasp the femae with muscular appendages.
Male strongylid nematodes have a muscular bursa, (B)formed from their cuticle, supported internally by muscular rays (R). Spicules (S) pry open the vagina to allow the ameboid sperm to enter.
Many monogeneans possess elaborate sclerotized rods in the terminal portion of the male reproductive tract.
