The gonads are the actual organs that produce the gametes . In most animals, individuals are either definite males or definite females. However, in some species, individual organisms are both male and female.
Hermaphroditism is when one organism has both sexes.
Earthworms and garden snails always have both male and female organs, and when, for example, two earthworms mate, they fertilize each other. A special variation on the theme is sequential hermaphroditism , in which an organism changes sex during its life. While most higher animals reproduce sexually, there are some species in which the females can, under certain conditions, produce offspring without mating. Parthenogenesis is the ability of an unfertilized egg to develop and hatch. This seems to be especially prevalent among insects.