Abstract
ABSTRACT The structure and distribution of the lobed glands in Porcellio scaber Latr. are described. The glands have a remarkable structure, each being deeply divided into many lobes, and provided with four nuclei which do not appear to be separated by cell membranes. They open externally at intervals along the margins of the body, on the lateral plates and uropods, always by separate pores, and always in exposed positions. The lateral plate and uropod glands resemble each other in many respects, but differ in size, staining reactions, and type of secretion. The glands do not differ in the two sexes, and are present in young animals newly liberated from the brood pouch. The glands of Porcellio scaber Latr. are compared with those of one species of each of the following genera: Asellus, Limnoria, Idotea, Ligia, Ligidium, Trichoniscus, Haplophthalmus, Oniscus, Platyarthrus, Hemilepistus, and Armadillidium. Lobed glands are peculiar to the terrestrial Isopoda (Oniscoidea), and appear to be present in all genera of this group, but no related structures are known in other Crustacea. They vary little in essential structure or distribution in the various genera. They vary considerably in size and number, but this variation is independent of sex, moulting condition, evolutionary position, respiratory mechanism, or humidity requirement. The lobed glands appear to have been evolved in adaptation to terrestrial life, but their function does not seem to be connected in any way with the problems of reproduction, moulting, respiration in air, or adaptation to dry surroundings.
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