Secernenteans: Secernentea

The life cycle of secernenteans generally goes from fertilization (FUR-teh-lih-zay-shun), or the joining of egg and sperm to start development, in the females through four stages of young and into adulthood. The young worms that hatch from the eggs usually resemble adults except they are smaller and their sex organs are not yet mature. Each of the four stages of young is separated from one another by complete shedding of the outer body layer. Most species of secernenteans have males and females, but in some species male and female organs are in the same worm.