The offspring emerging from the marsupium are in length. Various species have some form of ovisac or marsupium. Mature females have a well-developed marsupium. Peracaridans are characterised by having a marsupium in which they brood their young. Reproducing females bear a prominent brood pouch (marsupium) between their legs. Reproducing females bear a prominent brood pouch (marsupium) between their thoracal legs. The early developmental period is spent while young are within the marsupium of the mother. They then stay in the marsupium for about 100 days. Females carry the embryos in their marsupium for some time. The female has a marsupium (pouch) in the middle of her abdomen to carry offspring. The most obvious characteristic of the group is the marsupium in females. They develop for four-and-a-half months, then hatch in the marsupium. Unlike true shrimps (Caridea), females have a marsupium beneath the thorax. The word "marsupial" comes from "marsupium", the technical term for the abdominal pouch. During the process, the male inserts his penises into the marsupium and releases sperm.