The reproductive system of isopods was described in the early literature by various authors (see in Schobl 1880; Friedrich 1883; Leichman 1891; Nĕmec 1896a, b). The marsupium of the oniscid isopods is formed by five thoracic segments (Nos. 3–7). Four processes hang down from the thoracic epithelium; they are opaque or transparent, soft and surrounded by opaque mucus (Akahira 1956). There are three tubular evaginations per somite, called cotyledons, and the first somite bears only one (Patane 1940). When they shrink, the mancas (= larvae) hatch out of the marsupium (Schobl 1880 in Porcellio scaber). Verhoeff (1920) found that the cotyledons did not shrink within 42 days. There appears to be a relationship between the number of cotyledons and the habitat. More cotyledons were found in the more arid species (Lewis 1991).