The gonadal ridge, in turn, develops into a gonad. The female gonad, the ovary, produces egg cells. After migration primordial germ cells will become oogonia in the forming gonad (ovary). The male gonad, the testicle, produces sperm in the form of spermatozoa. Internal and external male genitalia development from bipotential gonad in embryo. The smooth endoplasmic reticulum is especially abundant in mammalian liver and gonad cells. This includes a decrease in reproductive hormone levels and gonad maturation. An ovotestis is a gonad with both testicular and ovarian aspects. The basic anatomy of "C. elegans" includes a mouth, pharynx, intestine, gonad, and collagenous cuticle. Hypogonadism without gonad destruction is reversible with treatment. When inside the gonad, it phagocytoses the sperm thus rendering the starfish infertile. This means that the sex of the animal is determined from an undifferentiated gonad. Both sexes have a single gonad located above the intestine. The nematode "Caenorhabditis elegans" has two spermathecae, one at the end of each gonad. Mutation of the Zinc fingers or inactivation of WT1 results in reduced male gonad size.