How do male and female amphioxi differ internally?

Male and female amphioxi are identical in their outward appearance, but they differ internally in the nature of their gonads, or reproductive glands.1

These animals are dioecious, meaning the sexes are separate. Internally, they possess 24 or more pairs of either ovaries or testes that form in rows along the wall of the atrial cavity. These reproductive structures lack ducts; when the gametes are ripe, the gonads rupture, spilling the eggs or sperm directly into the atrium. From there, the gametes are carried out into the sea by the water flowing from the cavity.21