sexually
Most invertebrates reproduce sexually. Diploid adults produce haploid gametes sperm and eggs . In some species, the same individuals produce both sperm and eggs. In other species, sperm and eggs are produced by separate male and female individuals. Fertilization occurs when a sperm and an egg fuse to form a diploid zygote. The zygote develops into an embryo and eventually into a new adult organism. On the way, it may pass through one or more larval stages. A larva plural, larvae is a juvenile, or immature, stage of an animal. It is generally quite different in form and function from the adult form of the species. For example, the larva may be able to swim freely, whereas the adult must remain permanently attached to a solid surface.