The origin and morphogenesis of cocoon-shell globules in the vitellaria ofDugesia lugubriss. l. have been investigated by means of ultrastructural and cytochemical methods. In the young vitelline cells with large nucleus and active nucleolus, numerous flattened cisternae of the endoplasmic reticulum and some Golgi complexes develop in the reduced cytoplasm. Adjacent to the Golgi complexes many vesicles are formed containing two kinds of material which the cytochemical tests revealed to be: (1) phenolic substances of high electron-density and (2) protein substances of medium electrondensity. Fusion of these vesicles results in the formation of membrane-bound globules which when fully mature have a phenolicprotein composition and a characteristic organization of dark and light concentric rings. Also the polyphenoloxidase system seems to be localized in the phenol containing vesicles and globules, as shown by the positive reaction observed at the level of these structures when catechol is added.
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